CONTAMINANTS IN COMPRESSED AIR SYSTEMS
ISO 8573 is the international quality standard for compressed air systems. Along with BRC, Primus, SQF and others, ISO 8573 identifies particles, water, total oil, gases and microorganisms as common contaminants in compressed air systems. These types of contaminants can come from a variety of sources. If contamination is present, then facilities will receive out of specification results. Then the detective work begins. If the tests do not meet the purity limits the user has set, then troubleshooting and remediation must take place. Perhaps a filter is inadequate or needs to be replaced, or there may be black iron piping in the distribution after the last filter. Regular testing allows users to identify the type of contamination that is affecting their system and helps to narrow down the timeline in which the contamination began. The BCAS recommends monitoring programs for compressed air systems with both direct and indirect impact on products (2020). SQF Edition 9 recommends a risk-based testing schedule, with a minimum of annually (2021).
Particles can be categorized as either viable or nonviable particles. Viable particles, or microorganisms, will be discussed later in this section. Non-viable particles include everything from rust, to dust and dirt, sand, and metal oxides to fragments of o-rings and tubing. The main sources of particle contamination are improper maintenance, damaged or inadequate filtration, rust, particle shedding hoses, and insufficient purging time after system alteration. Users sometimes choose filtration based more on pricing than on efficacy, which can prevent them from meeting their air quality requirements. Filters must be appropriate for the industry, have the correct efficacy, and should be changed at appropriate intervals as recommended by the manufacturer.
Maintenance performed on the system can cause particulate matter to accumulate down the lines. If there are additions to the distribution line, test results will sometimes show metal shavings or other debris left over from installation. It is essential to properly purge your compressed air and gas lines before taking a test - particularly if there has been maintenance or installation of additional lines, sampling or end user ports. Cycle purging can be used to flush out the lines and ensure that no particle contamination reaches the end product when the system is in use.
Water vapor in a compressed air system can lead to many issues down the line including microbial contamination and the degradation of pipes, o-rings, and tubing. The main sources of water contamination come from ambient air, accumulation in drops, dead ends or traps, leaks in the system, and rubber tubing.
There are large quantities of water in ambient air, particularly in the summertime as humidity levels rise. The intake air is generally high in moisture content. Because the air coming from the compressor is generally quite a bit warmer than the ambient air, it can often cause condensation (Henly, 2016). Even the smallest amount of water in the air over time can accumulate and pool in places like drops, dead ends, and traps. When water accumulates like this, it creates a very inviting environment for microorganisms to grow and thrive. It is critical to regularly empty and monitor these areas in your system. Dryers work to remove moisture from the air, but if there are no dryers employed, you can expect the compressed air to be quite wet.
Leaks are also a source of water vapor contamination in compressed air systems. Whenever the pressure drops, it creates a suction around the area of a leak that pulls ambient air into the system. If the leak is after the dryer or filtration, it can lead to water vapor contamination that impacts the air quality.
Oil can be present in compressed air systems as both vapor and as aerosol. It's important to work with an accredited laboratory that can analyze both types of oil and provide Total Oil results. Aerosols more commonly enter a system from the compressor itself. New installations or lack of proper maintenance can be a source of oil aerosol in the system.
Many food and beverage manufacturers are transitioning to oil-free or food-grade oil compressors to avoid excess machine oil that could be harmful to the end-products. However, even if your system is “oil-free”, testing regularly for oil contamination is still of critical importance. Oil vapor can enter the system from the intake air. Process solvents and cleaning solutions can be another source for oil vapors in the air that appear quite frequently in compressed air tests. Accredited compressed air tests can pinpoint these, and, once identified, procedures can be changed or altered.
Always purge after maintenance or changes to the compressor or distribution piping and ensure that filtration is appropriate for the system and purity requirements. Oil contamination can be detrimental to end products and should be carefully monitored.
Viable particles, or microorganisms, are often a headliner in the food industry. Dangerous microorganisms like Salmonella or E. coli can put reputations and bottom lines at risk. Manufacturing facilities have controlled environment processes and workflows, but it is essential to monitor that those are appropriate and happening at the correct intervals. Process fatigue happens in all industries and can allow dangerous microorganisms to pass through even the most thoughtfully designed cleaning protocols. Microorganisms are also very small in size and particles as small as 2 microns can squeeze through the compressors inlet filter and spread throughout the compressed air system (Atlas Copco, 2021).
Testing for bacteria, yeast, and mold allows manufacturers to understand what kinds of risks and where these organisms may be coming from. Further identification can also allow a user to dial into the root cause of this contamination.
Microorganisms can flourish in systems that are already contaminated by water, oil, and other particles. Contaminated systems allow microorganisms to grow abundantly. Infrequent or inadequate maintenance can allow microorganisms to be introduced to the system and then subsequently spread throughout it. Additionally, if hygienic processes are not set in place and followed carefully, compressed air systems can end up blowing particulate matter and microorganisms onto food products (Brownlee, 2020).
Gaseous contamination is of concern to those using modified atmospheric packaging or creating products that use gases for taste or color. In addition to testing for purity, it’s also important to test for contamination in the gases.
Much like compressed air, pure gases are susceptible to particle, water, oil, and microbial contamination. Gaseous contamination, such as too much oxygen in a nitrogen line can impact products negatively and force users to throw away or discard the product. Gas contamination can enter the system from the intake, distribution piping leaks, or from a malfunctioning compressor.
SAMPLING POINTS AND FREQUENCY
The goal of compressed air testing is to find contamination in the system if it exists to an extent that could be damaging to the end product. Because of this, a single sample one time a year does not adequately represent the health and quality of the compressed air system. Though annual testing is all that is technically required per SQF and BRC, it's recommended to test on a risk or maintenance-based schedule.
Finding contamination in the system is the only way to get to the source and remediate the problem. Quarterly testing or testing before and after maintenance helps to ensure that all the scheduled maintenance and protocols are adequate and functioning as expected. There are some cases where filters need to be replaced more often, or changes to the workflow need to be implemented.
Compressed air contamination can come from many sources, and it's important to have an in-depth understanding of your system and its risks. Though each system is unique, the table above is a helpful tool in investigating different types of contamination. Regular testing is the best way to first identify contamination, and then track down the source so it can be remediated. The experts at Trace Analytics are here to help make sampling and understanding your reports easy. With over 3 decades of compressed air testing experience, the AirCheck team can walk you through common sources of contamination as well as help troubleshoot your sampling techniques. For more information on compressed air testing, please contact us at firstname.lastname@example.org.
Atlas Copco. (2021).
What contaminants can be found in compressed air? Atlascopco. Atlas Copco. https://www.atlascop...aminants-in-air.
BCAS urges best practice compressed air guidance is maintained during lockdown. BCAS urges best practice compressed AIR guidance is maintained DURING LOCKDOWN. https://www.bcas.org...ractice-84.aspx.
Brownlee, B. (2020).
Keep contaminants out of food and beverage processing air supplies. Keep Contaminants Out of Food and Beverage Processing Air Supplies | Compressed Air Best Practices. https://www.airbestp...ng-air-supplies.
Heney, P., & 4 Reasons Your Air Compressor Has Water In It – Air compressor repair knowledge at your finger tips. says: (2016).
Why is there water in my compressed air system? Pneumatic Tips. https://www.pneumati...ssed-air-system.
- Sep 21 2021 02:44 PM
- by Simon
CHANGES TO SQF CODE
SQF Edition 9 comes with several enhancements and improvements to the code structure, methodology, and technical requirements. Below are the relevant compressed air and gas updates and how they pertain to the health of your compressor system and quality system alike.
SQF Edition 9:
The new addition in Module 11 states, “The frequency of analysis shall be risk-based and at a minimum annually.”
- 22.214.171.124: Compressed air or other gases (e.g. nitrogen or carbon dioxide) that contact food or food contact surfaces shall be clean and present no risk to food safety.
- 126.96.36.199: Compressed air systems and systems used to store or dispense other gases that come into contact with food or food contact surfaces shall be maintained and regularly monitored for quality and applicable food safety hazards. The frequency of analysis shall be risk-based and at a minimum annually.
Because manufacturing facilities vary so dramatically in their needs, procedures, systems, and workflows, it is critical for each to assess their individual risks. A compressed air risk assessment is a great place to start. Risk assessments account for everything from system age, to piping distribution, to filtration and dryers. Knowing where your system stands, what its limitations are, and how it could contribute to contamination can help determine the frequency and stringency of analysis.
Annual testing, at a minimum, allows manufacturers to understand their system at that point in time. More frequent monitoring allows users to create a trend analysis and understand how seasonal changes, maintenance, and other factors can affect the quality of their compressed air or gas. Of course, each facility has unique needs and risks, but the annual requirement of analysis helps to set a minimum benchmark for manufacturers.
In appendix 2, users will find this definition of compressed air monitoring:
- A program that includes particles, water, oil, microorganism, and gases in compressed air and other gases. A verification of effectiveness of compressor maintenance and filtration a management facility has in place.
Leaks in distribution piping can provide contaminants a way to infiltrate the system. Maintenance without proper purging can introduce contamination into a system and should be considered a potential source of risk. Additions or changes to a system may leave the piping or valves vulnerable to contamination as well. Trace Analytics recommends sampling after any major repair work to ensure that the air quality has not been negatively impacted. If changes are made to a system and the system is not effectively purged, contaminants like particles, water, and oil can be left behind. Without proper monitoring, contamination could remain in the system, and if left unchecked, could impact the end-product.
WHO IS IMPACTED BY THESE CHANGES:
SQF Edition 9 has expanded and modified codes from previous editions. This change has introduced compressed air monitoring to some codes where it previously hadn’t been included. Compressed air requirements can be found in:
• Food Manufacturing
• Pet Food Manufacturing
• Animal Feed Manufacturing
• Animal Product Manufacturing
• Dietary Supplement Manufacturing
• Storage & Distribution
• Manufacturing of Food Packaging
If your facility falls into any of these categories and you use compressed air in your processes, you will be required to monitor your compressed air and gas systems at least annually (or more frequently based on your risk assessment) to ensure product safety.
WHAT TO TEST FOR:
SQF Edition 9 points to particles, water, oil, microorganisms, and gas testing for manufacturing facilities. Each facility is unique and has individual requirements, so it is essential for each user to conduct a risk assessment and compare with published standards, like ISO 8573, to choose the right purity levels for their systems. Higher risk end-products may require more strict purity levels. Some end-products may require strict particle testing, but have lower limits for water vapor.
It is also important to consider the capabilities of your system and ensure that your purity classes are achievable and appropriate. For example, black iron pipes are going to have a great deal more rust accumulation than stainless steel pipes. Systems with refrigerated dryers are going to have more moisture than systems with desiccant dryers.
ISO 8573 is an international compressed air standard that provides purity classes for particles (viable and nonviable), water, and total oil, allowing users to choose the appropriate ranges for their use. This standard can be used as a “common language” between users, laboratories, and compressed air system suppliers.
Particles can be categorized as viable and non-viable. Viable particles are microorganisms, which will be discussed below. Non-viable particles are characterized by their size, shape, transparency, color, and material. They are of great concern to many manufacturers. No one wants to find metal shavings in their coffee grounds. Metal shavings, rust, bits of tubing and plastics are all examples of particles that might be found in a compressed air system. ISO 8573 designates size ranges with limits for each purity class to help manufacturers ensure that their filtration systems are functioning properly. If your point-of-use filter is supposed to filter particles size 0.3um and up, and your compressed air tests reveal particles sized 0.5-5, then you will need to troubleshoot your filtration and distribution lines after filtration.
Water in compressed air systems is concerning as it often leads to much bigger problems. Excess water can cause piping to rust, producing particles. This contamination can also create a breeding ground for dangerous microorganisms and saturate filters, rendering them useless. ISO 8573 offers 6 purity classes to accommodate users with either desiccant or refrigerated dryers.
Oil vapors and oil aerosols together are known as Total Oil. Stricter limits require both aerosol and vapor testing combined. In less strict classes, oil aerosol alone can be monitored. Depending on your risk levels, you can choose the appropriate class for your system. Even if you have an oil-free compressor, maintenance oils, oils from cleaning supplies, and vehicle exhaust can infiltrate the system. It is not enough to simply replace your compressor with an oil-free one. If you’ve previously used a traditional compressor, there could be oil left in the pipes or distribution system. Regular monitoring helps ensure oils are not impacting your end-products.
Microorganisms (Viable Particles):
Viable particles, or microorganisms, can be hugely detrimental to your end-products, bottom line, and reputation. Contamination from microbes like Listeria, or Salmonella should be monitored for regularly if manufacturing consists of dairy products. Microbes can live in compressed air systems, particularly if these systems are contaminated by oil, particles, and water. These dark, wet breeding grounds can put products at risk. ISO 8573-7 recommends testing with an impaction sampler and incubating contact plates for a minimum of 10 days. Some companies may have specific indicator microorganisms that they are concerned about and need to do further identification.
HOW TO SET UP A MONITORING PLAN:
Setting up a monitoring plan is an important part of ensuring the quality of your compressed air system and meeting your certification requirements. SQF Edition 9 mentions particles, water, oil, microorganisms, and gases as contaminants to monitor. Using ISO 8573 purity classes along with a compressed air risk assessment, a user can determine how strict their limits should be.
Where to sample:
A common question from manufacturers is where to take the samples. Results from your air samples should be representative of their use on the product. If your compressed air directly impacts your products, you’re going to want to test at the point of use. Tests at the compressor can help users understand the quality of the air at the start of the system. Testing can also be performed midway through the line to understand the impact that the distribution system may have on the quality of that air.
Number of Samples:
The number of samples is also one that must be determined by the manufacturers. If you have 20 points of use, you may want to test them in rotating percentages. Testing 25% of the points of use quarterly could be an appropriate and manageable way to test each point annually. This would dictate only 5 samples per quarter. Some users may choose to test each point of use that impacts end-products. Others may choose to test at the compressor and then at the end of the line only. While a single test point does meet the minimum requirement, it hampers the ability to perform seasonal trend analysis.
Frequency of sampling:
It’s then necessary to consider how often testing should take place. SQF Edition 9 cites annually - at a minimum. Many manufacturers choose to test quarterly or semi-annually to build a trend analysis and see how their system changes over time, reacts to maintenance schedules, and handles seasonal changes.
Each facility is unique and each monitoring plan will be as well. Depending on the risk levels, the type of system, and the usage of the compressed air, a users’ monitoring plan should fit their needs. Third-party, ISO 17025 accredited laboratories, like Trace Analytics, LLC can help implement a monitoring plan, schedule testing, and provide reliable and expedient air quality results.
Preparing your compressed air system for the new Edition 9 improvements means your facility won’t be left unprepared. With the release of SQF Edition 9 comes the opportunity for manufacturers to address their quality systems, risk assessments, and monitoring plans for their compressed air systems. With added guidance from SQF, users can determine what contaminants to test for, how often to test them, and create a plan to ensure they maintain appropriate levels of quality year-round. For more information on compressed air testing, please contact the experts at Trace Analytics, LLC.
512-263-0000 ext 5 | email@example.com
By Jenny Palkowitsh, Trace Analytics, LLC
Chuboff, L. (2021, March 05). Sqf code edition 9: What's changing and how to prepare. Retrieved March 10, 2021, from https://www.sqfi.com...how-to-prepare/
Sqf code downloads. (2021, January 12). Retrieved March 01, 2021, from https://www.sqfi.com...on-9-downloads/
- Apr 05 2021 04:33 PM
- by Simon
ISO 8573 has 9 parts, with one dedicated specifically to particle contamination (ISO 8573-4). Section 4 mentions liquid, viable, and non-viable particles as possible contamination in compressed air. The focus of this article will be on analytical methods for non-viable particle contamination specifically.
According to ISO 8573-4, non-viable particles are characterized by their size, shape, transparency, color, and material. ISO 8573 provides purity classes based on size ranges for particles. Learn more in the chart below.
TYPES OF PARTICLE ANALYSES
Gravimetry, microscopy, laser particle counters, and SEM are methods that can be used to test for particle contamination in compressed air. Not all types of analysis are appropriate for all systems or specifications. It is critical to work with a third-party accredited laboratory to ensure your results are accurate and that the type of testing performed is right for your facility’s needs.
Gravimetry is the analysis of particles by mass. Sampled on a filter membrane, compressed air is passed through and any particles are captured on the membrane. The filter is then transported to a third-party laboratory and weighed. According to ISO 8573, gravimetry is appropriate for the analysis of particle contamination for applications that require a Class 6, 7, or X.
Sampling for gravimetric analysis takes only about 5 minutes and requires about 250 liters of air. It is important that ambient air does not impact the filter membranes as ambient air is often full of particles. Depending on the facility, there could be dust, powder, plastics or other non-viable and viable particles circulating in the air. Gravimetric analysis must consider the influence of temperature, pressure, water vapor, and other contaminants (Ochoa, 2016).
Filter membranes can capture oil aerosol in addition to particle contaminants, and in some cases, it may be necessary to separate the two. Maria Sandoval, Laboratory Director at Trace Analytics, LLC, states: “Gravimetry relies on pre and post weights of filter membranes upon fabrication and sampling respectively. If sampled weight exceeds a specification limit, oil aerosols can be extracted, the filter reweighed, and oil aerosol concentration extrapolated.”
Low risk applications can consider gravimetry in order to ensure that their compressed air meets requirements laid about by ISO 8573 or their corporate standards.
Microscopy allows for the characterization of particles by size and shape. Light Optical Microscopy is an appropriate method of analysis for purity classes 3-5. This method allows for the lab technician to categorize the particles by size, group them into ranges, and then count the totals. Sampling for purity classes 3-5 lasts only about 10 minutes, and requires a minimum of 500 liters of air volume. Once air passes through the filter membrane, it is returned to the lab for analysis by trained lab technicians and scientists.
“At Trace, we use Bright Field Microscopy to analyze filter membranes that may be contaminated with particles. Depending on the specification, we can use high or low objective to bin the size particles for reporting. In the event that further particle characterization is required, the filter membrane can be sent to scanning electron microscopy for further analysis,” Sandoval states. For most applications, microscopy is appropriate and allows manufacturers to meet their requirements.
Sandoval mentions that there are both advantages and disadvantages to using microscopy: “Using this technique, not only can a particle be sized, but its characterization can also be determined (e.g. color, topography). This requires the use of technician-driven analysis, which can be time consuming.”
Laser Particle Counter
Laser particle counters also report the number of particles in different size ranges. Compressed air is passed through a high pressure diffuser and then through an LPC which analyzes the size and number of particles present in the air at that time. Companies with higher risk applications, often pharmaceutical or high-risk food manufacturers, will opt for laser particle counters in order to reach purity classes 1 and 2. Expensive and sensitive instruments, laser particle counters can provide on-site test results and can act as troubleshooting devices (Ochoa, 1999).
Sandoval notes that, “LPC’s have limitations such as, but not limited to, the lowest size particle they can detect. When researching use of LPC for particle analysis, the facility should always consider the particle range their facility specification requires to be reported to. Also note that LPC’s are limited because they’re calibrated to spherical, standardized particles, so if an irregular shaped particle crosses the laser, the LPC will assign the closest sized spherical range to that irregular shaped particle.” This creates a disadvantage for use of LPC for reporting particle analyses as they can only differentiate by size; however, particles can be reported instantly, saving the manufacturer time. Instant results represent a time-saving opportunity, but the lack of size differentiation might not be appropriate for all applications.
Scanning Electron Microscope (SEM)
In some circumstances, manufacturers will want further identification, or need additional help troubleshooting contamination. SEM (scanning electron microscopes) can reveal the texture and chemical composition of particulates. According to Metallurgical Engineering Services, “the scanning electron microscopes will allow you to view surface features at 5 to 300,000X magnification to provide you with high quality, depth of field images. When used with EDS detectors attached to each SEM, the chemical composition of surface features is quickly attained” (2019). Analyzing particles using SEM is advantageous over use of optical microscopes as it provides a focus on irregular fracture surfaces. For most applications, this level of specificity is not necessarily required, but it can be employed as a type of particle analysis.
RISKS OF CONTAMINATION AND INAPPROPRIATE ANALYSES
Contamination poses a great risk both to the safety of the product and to the efficacy of the system. Inappropriate analysis could cause serious contamination to be missed. It could also be overly stringent, causing a failed test result when air quality was at an acceptable level.
Particle contamination can occur from a variety of sources. The compressed air system itself is often a major source of contamination. Rusty pipes, the use of mixed metals, polymer hoses, o-rings, damaged filters or solder can all result in particle contamination of compressed air or gas. Maintenance events or system alterations can also negatively impact the quality of the system. Ambient air has tons of particles and when a system is exposed to ambient air, even for a short period of time, the system can become contaminated. Because particles can originate from so many different places, and can appear in many different sizes and shapes, it is critical for a manufacturer to understand their system’s risks and the necessary specifications they should adhere to.
Any particle contamination can be harmful to consumers. No consumer wants metal shavings in their coffee grinds. Performing a risk assessment can help manufacturers determine the unique challenges their system might face. This can also help determine which kind of particle analysis is best suited to their requirements.
Manufacturing industries can ensure product safety and quality through appropriate analysis of particle contamination in their compressed air systems. As individual facilities encounter varying risks, careful determination of particle analysis methods should be made in order to meet ISO 8573 or corporate standards.
Analysis through gravimetry, microscopy, laser particle counters (LPC), and a scanning electron microscope (SEM), can each be employed to determine particle contamination depending on the necessary requirements.
TESTING WITH TRACE ANALYTICS, LLC
Trace Analytics, LLC is an ISO 17025-accredited laboratory specializing in the analysis of compressed air. Testing at Trace includes the analysis of particles, water, and oil contamination according to ISO 8573 standards through the use of gravimetry, microscopy, and Laser Particle Counter (LPC) techniques. To learn more about compressed air testing for particle contamination and packages offered at Trace, visit www.AirCheckLab.com.
ISO 8573-4:2019. International Organization for Standardization
Metallurgical Engineering Services. “SEM Analysis - Metallurgical Engineering Services.” Metallurgical Engineering Services, 2019, metengr.com/testing-services/metallurgical/sem-analysis/. Accessed 29 Aug. 2019.
Ochoa, Ruby. “Sampling and Testing for Compressed Air Contaminants.” Sampling and Testing for Compressed Air Contaminants | Compressed Air Best Practices, Air Best Practices, 2016, www.airbestpractices.com/standards/food-grade-air/sampling-and-testing-compressed-air-contaminants.
Sandoval, Maria. “Particle Analysis at Trace Analytics.” 28 Aug. 2019.
- Jun 29 2020 05:47 PM
- by Simon
Contamination of compressed air and gases used in beverage manufacturing can lead to beverage recalls, reduced product shelf life, changes in taste and appearance of products, and overall lost profits and a tarnished company reputation. For example, in 2001, one of the largest food and beverage companies in North America recalled over 140,000 cases of product due to contamination with a compressed air system lubricant (1).
Food-borne illnesses alone are estimated to cost the United States $93.2 billion annually, a hefty increase from the $77.7 billion estimated in 2012 (2). Beverage companies applying Hazard Analysis and Critical Control Point (HACCP) principles, included in the International Standards Organization (ISO) 22000 Food Management System (3), deem compressed air and gases as critical control points, vital to beverage safety [Table 1]. International food safety standards exist to hold beverage manufacturers accountable for the safety of their products.
[Table 1]- Examples of critical control points for compressed air and gases in beverage manufacturing (20,21,22,23,24).
Major global and national standards and organizations, including the ISO (4), the British Compressed Air Society (BCAS) (5), the British Retail Consortium (BRC) (6), the Safe Food Quality Institute (SQF) (7), the Global Food Safety Initiative (GFSI) (8), and the U.S. Food and Drug Administration (FDA) (9), mandate or suggest monitoring of compressed air and gases used in beverage manufacturing. While compressed air and gas testing has become a requirement for these major food safety standards and organizations, specifications for compressed air and gases are few and far between. ISO 8573 has laid the groundwork for developing limits [Table 2] for contaminants in compressed air and gases. This standard considers particles (non-viable and viable), water, and oil as the key contaminants to monitor (4). The procedures outlined by ISO 8573: 1-9 can be modified to address pure and mixed compressed gases as well as gas distribution systems.
BCAS goes further in setting compressed air and gas standards for the beverage industry. BCAS recommends ISO 8573 purity classes to follow for indirect contact, purity classes 2:4:2 (non-viable particles: water: oil), and direct contact, purity classes 2:2:1 (non-viable particles: water: oil), of products with compressed air and gases in beverage manufacturing processes (5).
Beverage companies may test compressed air and gases used in their manufacturing solely to meet various standard guidelines; however, compressed air and gas testing also provides insights and important metrics that can be used to benefit and improve the quality of their beverage products and safety schemes. Annual testing, while sufficient to meet most international food safety standards, may not be enough to establish compressed air and gas quality trends. Testing frequency is a topic rarely discussed, but essential to leveraging compressed air and gas testing to benefit beverage quality. Key factors of compressed air and gas, particles (non-viable and viable), water, oil, gas purity, and gaseous contaminants, will be discussed with regards to their relationship to beverage quality and safety. Compressed air and gas testing is a vital supplement to compressor purification systems for ensuring that the compressed air and gases used in beverage manufacturing conform to industry standards and pose minimal risk to beverage quality and safety.
[Table 2]- ISO 8573 purity class. Include microbial contaminants.
Particles (non-viable and viable):
ISO 8573-4 discusses methodology for determining particle content (4), both liquid and solid; examples of particle contaminants include metal shavings, glass, tapes, rubbers, insect parts, plant debris, oil, liquid water and microorganisms. Particles can be introduced into beverage products from the ambient air intake and/or as a byproduct of the pneumatic machinery and engine combustion of the compressed air system.
When viable particles, or microorganisms (bacteria, yeast and mold) are required to be reported, ISO 8573-7 can be employed. While specifications for microbial contamination of compressed air and gases do not exist in the current standard, they should always be a result of a risk assessment by the quality department of the sampling facility. Particle contamination in beverages can result in changes to the taste, color/appearance, and texture of the final product. Consumers won’t want to drink beverages containing unidentifiable particulates as this could suggest unhygienic business manufacturing practices and/or a tainted beverage product. Particle contamination, especially by viable particles, jeopardizes the safety of the beverage and can result in lost profits and sick and unhappy customers. Proper filtration, with size limits appropriate for the diameter of the particle desired, should be employed just at the point-of-use and after the outlet area of the storage tank prior to the distribution system in order to prevent particle contamination of beverage products.
Per ISO 8573-3, water is measured in terms of pressure dew point, or the humidity of the compressed air (4). Ambient air, containing moisture, introduces water to the compressed air or gas system (10). To dry the compressed air before use, a series of air dryers and filter systems should be employed. Compressors lacking drying systems may result in water condensate and ultimately lead to a misting of the final product, which can impact the balance and homogeneity of beverage ingredients (11). High moisture content in compressed air and gas is harmful to the compressor system and leads to the creation of corrosion and metal oxides, such as rust (10), non-viable particles under ISO 8573 (4). These newly produced contaminants, which will exit the compressor system and make their way into beverage products, can affect the taste and appearance of beverages. Perhaps the biggest danger with moist compressed air is the creation of an ideal environment for certain microbes to grow, such as mold (11, 12). Thus, contamination generates additional contamination, and one can see the significance of water contamination to microbial and non-viable particle contamination.
Oil contaminants behave similarly to water in that they can both condense and vaporize. However, due to the weight of oil, a pressure drop will occur, slowing the efficacy of the compressor system (13). Oil in various forms, including as liquid, aerosol, and vapor, is considered under ISO 8573-2 & 5 as a major contaminant to monitor in compressed air. Oil contamination can originate from ambient air and/or the compressor itself, especially when using compressors that require lubricants in the compression chamber (14, 15). Oil contamination can result in recalls and can ruin beverage products by giving them off-flavors and an altered appearance and consistency. In beer, oil can flatten the frothy head and ruin the experience of the consumer (16). Oil contamination may also increase risk for microbial contamination by providing nutrients needed for microbial growth (17). Food-grade lubricants may help reduce the risk of harmful oil contamination reaching final beverage products, but this may not always be financially feasible as food-grade lubricants can be more costly upfront (18), compared to traditional industrial oils. These food-grade lubricants are still regulated and only minimal contact with food and beverage products is permitted (19).
Gas Purity and Gaseous Contaminants:
Compressed pure gases and mixtures of gases are used in beverage manufacturing for bottling, aeration, fermentation, carbonation, nitrogenation, and preservation (20,21,22,23,24, 25). The gases typically used in these applications include nitrogen, carbon dioxide, argon, and sulfur dioxide. Proper gas purity, with minimal to no gaseous contaminants, is vital to maintaining control and consistency with beverage manufacturing processes and for ensuring the quality and safety of the final product. Gaseous contaminants are often present in both compressed air and gases, originating from ambient air and/or within the compressor, and ISO 8573-6 considers carbon monoxide, carbon dioxide, sulphur dioxide, hydrocarbons (C1 to C5), and oxides of nitrogen as gaseous contaminants to measure. However, gaseous contaminants are not considered major contaminants per ISO 8573 and no purity classes are specified, leaving the beverage manufacturer to decide which gaseous contaminants (if any) to measure and appropriate limits to set for the given application.
Sulfur dioxide is a regulated gaseous contaminant, often used in beverage manufacturing for preservation and antimicrobial purposes, with limits set by the FDA and European Union (25, 26, 27, 28). Oxygen is of major concern to beverage manufacturers due to its oxidative effects. Excess oxygen can result in the creation of off-flavors and the degradation of colors, flavors, and clarity of the beverage product (29, 30, 31). In the case of fermented beverages, such as beer and wine, oxygen is needed during fermentation as yeast require oxygen to grow and expand (30, 31). However, after fermentation has begun, oxygen, even in small quantities, can result in stale/off-flavors, a hazy and/or mis-colored product, and a reduced shelf-life stability (30,31). Carbon dioxide is one of the most well-known of gases used in beverages and imparts effervescence, a tangy taste, and aids in the prevention of spoilage (32). The International Society of Beverage Technologists Carbon Dioxide Guidelines set forth recommendations for ensuring the quality of carbon dioxide used in beverage manufacturing (33) [Table 3]; the suggested limits for gaseous contaminants listed may also be used as a guide for other compressed gases.
[Table 3] International Society of Beverage Technologists Carbon Dioxide Guidelines (32).
Beverage manufacturers should consider their processes and perform a risk assessment to determine which gaseous contaminants and limits to use.
One of the most commonly posed questions to third party testing laboratories relates to the number of times a point-of-use needs to be tested in a calendar year. Facilities adhering to the BCAS Guidelines test compressed air quality twice per year or per the manufacturer's recommendations. ISO 8573 standards do not mention testing frequency and act only to provide methodologies and references for testing and limits. This leaves the sampling facility with the task of determining how often testing should be conducted. Often facilities will utilize risk assessments and HACCP training programs to establish a monitoring schedule. When a monitoring plan is initiated, the first data point is commonly referred to as a baseline, or the initial state of contamination for the point-of-use of the compressed air or gas system. Monitoring these critical check points and critical limits should always require procedures (trend analysis) that detect loss of control at the monitored site in real-time and over an extended period (34). When real-time analysis is conducted of a high-risk point-of-use, action and alert levels can be designated to signal drift from historical performance measurements (35). The facility can then develop a strategy to respond to these trends in line with the desired outcome. Trend analysis works best when multiple data points are available throughout a year. Too many data points and the information is redundant, too few and the information is inadequate. When done well, trend analysis can even give facilities ideas about how to change preventive maintenance and cleaning schedules to move results in a more predictable fashion.
Compressed air and gases are a vital utility and additive for beverage facilities today. However, this utility is susceptible to various types of contamination which can affect the quality and safety of beverage products, ultimately hurting a beverage company’s bottom line. While it is the duty of beverage companies to orchestrate a fine-tuned monitoring plan that analyzes all possible contaminants that can harm consumers, it is also in the best interests of beverage companies to complete extensive testing to improve and protect the quality of the beverages they produce. Combining air and gas treatments, such as dryers and filters, with regular monitoring enables beverage companies to ensure the quality of the compressed air and gases used in manufacturing. Monitoring the status of contaminants in compressed air and gas is an important step towards maintaining brand integrity, customer favorability and beverage quality and safety. For more information on compressed air and gas testing, contact us at firstname.lastname@example.org.
By: Maria Sandoval and Robert Stein of Trace Analytics, LLC
Maria Sandoval has over 15 years of experience in Microbiology and Molecular Biology. Her field work includes analyzing extremophiles isolated from the depths of Lake Baikal in Russia to the 50km exclusion zone of Chernobyl. Additionally, she’s worked alongside the CDC with DSHS analyzing and diagnosing patient microflora. Her tenure with the Lawrence Berkeley National Laboratory, Department of State Health Services and the University of Texas MD Anderson Cancer Center has made her a leading expert in microbial testing. As Trace Analytics’ Microbiologist and Lab Director, she is responsible for microbial testing and procedural development.
Robert Stein is a U.S. appointed expert on the ISO 8573 Compressed Air Testing Technical Committee and holds a BS in Chemistry and Archaeology and an MS in Forensic Chemistry. Robert has gained experience in varied scientific roles, including forensic anthropology, trace chemistry, molecular and cell biology, and clinical toxicology. Experienced in analytical chemistry and microscopy, he currently serves as the Quality Manager at Trace Analytics.
Trace Analytics is an A2LA accredited laboratory specializing in compressed air and gas testing for food and beverage manufacturing facilities. Using ISO 8573 sampling and analytical methods, their laboratory tests for particles (0.5-5 microns), water, oil aerosol, oil vapor, and microbial contaminants found in compressed air. For over 29 years, they’ve upheld the highest industry standards of health and safety, delivering uncompromising quality worldwide in accordance with ISO, SQF, BRC, and FDA requirements. Visit www.AirCheckLab.com
1. Hui, Y. H., Bruinsma, L. B, Gorham, J. R., Nip, W., Tong, P. S., and Ventresca, P. (2000). Food Plant Sanitation. New York: M Dekker.
2.Filipic, M. (2015, June 3). High Cost of Foodborne Illness: New Study Provides State-by-State Breakdown. Retrieved February 24, 2019 from https://cfaes.osu.ed...state-breakdown
3. ISO 2200. International Organization for Standardization. (2019)
4. ISO 8573. International Organization for Standardization. (2019)
5. Food and Beverage Grade Compressed Air Best Practice Guideline 102. British Compressed Air Society Limited.
6. Global Standard for Food Safety: Issue 8. British Retail Consortium. (2018)
7. SQF Code, Edition 8. Safe Quality Food Institute. (2017)
8. GFSI Benchmarking Requirements: Verision 7.2. Global Food Safety Initiative. (2018)
9. Doc. No. 21 CFR 110. U. S. Food and Drug Administration. (2018)
10. Parker. (2014, October/November). Retrieved February 26, 2019 from https://www.foodsafe...-food-industry/
11. Ochoa, R. The Major Contaminants in Compressed Air. (2016) Retrieved April 2, 2019 from https://www.ifsqn.co...pressed-air-r52
12. U.S. Environmental Protection Agency. A Brief Guide to Mold, Moisture and Your Home. Retrieved April 1, 2019 from https://www.epa.gov/...e-and-your-home
13. Atlas Copco. The Quality of Compressed Air. Retrieved April 2, 2019 from https://www.atlascop...sed-air-quality
14. Atlas Copco. What Contaminants Can Be Found in Compressed Air? Retrieved February 26, 2019 from https://www.atlascop...aminants-in-air
15.Ryan, D. and Hannifin, P. ISO 8571.1. Retrieved February 24, 2019 from https://www.airbestp...-purity-classes
16. Atlas Copco. Improving Beer Brewing Quality with the Right Air Compressor. Retrieved April 1, 2019 from https://www.atlascop...nd-beer-brewing
17. Scott, L. Compressed Air GMPs for GFSI Food Safety Compliance. Retrieved April 2, 2019 from https://www.airbestp...fety-compliance
18. Palkowitsh, J. (2018, November 30). The Impact of Oil Contamination in Food Grade Compressed Air. Retrieved April 2, 2019, from https://www.ifsqn.co...pressed-air-r64
19. Gebarin, S. (2009, January 1). The Basics of Food-grade Lubricants. Retrieved April 2, 2019, from https://www.machiner...bricants-basics
20. Compressed Air and Gas Handbook (7th ed.). (2016). Retrieved April 1, 2019, from https://www.cagi.org...electhb_ch1.pdf
21. Food and Beverage - Oil-Free Air. (n.d.). Retrieved April 1, 2019, from https://www.ingersol...ndbeverage.html
22. Draft Beer Made Easy - Draft Beer Gas The Basics. (n.d.). Retrieved April 1, 2019, from http://www.draft-bee...aftbeergas.html
23. Reble, A. (2016, March 16). Let’s Talk about Gases…in Winemaking. Retreived April 4, 2019, from https://www.wineshop...-in-winemaking/
24. Grennier, M. (n.d.). Clean and Dry Compressed Air Drives Success at Five Churches Brewing. Retrieved April 4, 2019, from https://www.airbestp...hurches-brewing
25. Carel, M. (2011, October 11). Sulfur dioxide (SO2) in wine. Retrieved April 4, 2019, from https://winobrothers...de-so2-in-wine/
26. Doc. No. 21 CFR 130.9 (2018)
27. England, European Parliament, Council of the European Union. (2008). REGULATION (EC) No 1332/2008 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 16 December 2008 on food enzymes and amending Council Directive 83/417/EEC, Council Regulation (EC) No 1493/1999, Directive 2000/13/EC, Council Directive 2001/112/EC and Regulation (EC) No 258/97 (pp.1-9).
28. News Medical Life Sciences. (2004, May 19). Survey of Sulfur Dioxide in Soft Drinks. https://www.news-med...05/19/1659.aspx
29. Walker, C. (2013, January 11). The impact of natural ingredients on the manufacture of soft drinks. Retrieved April 4, 2019, from https://www.newfoodm...of-soft-drinks/
30. Smith, B. (2015, June 18). Why oxygen is bad in your home brewed beer. Retrieved April 5, 2019, from https://beersmith.co...me-brewed-beer/
31. Vinifera, V. (n.d.). Why is oxidation bad for why? Retrieved April 2, 2019, from https://www.winespec...ation-Bad-53941
32. ISBT Carbon Dioxide Guidelines. 1999. International Society of Beverage Technologists.
33. Ringo, S.M. (2001, January). International society of beverage technologists carbon dioxide guidelines. Retrieved April 3, 2019, from https://www.foodsafe...ide-guidelines/.
34. Sandle, T. (2018, July 27). Use of hazard analysis and critical control points (HACCP)-Part 1: Assessing Microbiological Risks. Retrieved April 2019, from http://www.ivtnetwor...iological-risks
35. McAteer, F., & Burke, R. (2008, April). Getting the bugs out- An effective environment monitoring program begins with interpreting applicable international standards. Clean Rooms-Microbial Monitoring. Retrieved April, 2019, from https://books.google...nalysis&f=false
- Jun 29 2020 05:50 PM
- by Simon
HACCP and Compressed Air
The new rules created by the FDA to fulfill FSMA require that manufacturers must conduct a Hazard Analysis (HA) as part of the revised current Good Manufacturing Practices (cGMP). Hazard Analysis serves to identify and inform Critical Control Points. Critical Control Points (CCP) are steps, stages, or points in a process where a failure of a standard operating procedure or equipment could lead to the contamination of product and resulting harm to consumers. Together, Hazard Analysis and Critical Control Points are referred to as HACCP. Each identified CCP must be monitored, and such monitoring must be documented. The HACCP process informs the frequency and tolerance of that monitoring. For example, if milk must be pasteurized to a temperature of 161 F, the step of the process that heats the milk is a Critical Control Point, and the functioning of the equipment and temperature achieved must be monitored and documented.
Often, Critical Control Points are less obvious. In the context of compressed air and gas, if a facility uses compressed air to cause a product to flip at a certain point, that compressed air is in direct contact with the food and becomes a potential source for contamination. Compressed air that is used to clean a surface that is used to prepare food has indirect contact with that food. Obviously, air or gas that is in direct contact food poses a more significant risk than gas that only indirectly contacts food, but both are still Critical Control Points.
Common utilizations of compressed air or gas that are in direct contact with food include drying, sorting, freezing, moving, carbonating, culturing, inert packaging, and modified atmosphere packaging. Some examples of indirect contact of compressed air or gas with product include cleaning of surfaces, packaging manipulation and pneumatically driven equipment. Each of these represent a Critical Control Point.
Contamination of Compressed Air
Depending on the compressed air or gas system, contamination can take several forms and have multiple sources. Common contaminants of compressed air or gas include solid particulates, oil vapors and aerosols, water vapor or aerosol, and viable microbial contamination. Particulates are commonly a consequence of friction within the system. They can originate from unions, valves, seals, and other fittings, as well as the moving parts of the compressor itself. They may also be a consequence of the ambient air the compressor intakes for the system. Oil vapors and aerosols are commonly a consequence of compressor pump oil, but may also originate from cleaning materials, solvents, and contamination of the ambient air the compressor intakes. Water vapor and aerosol originate from the ambient air used by the compressor. Microbial contamination is ubiquitous, and may be present in the ambient air, on the equipment at the time of install, or contamination at the point of use. Microbial contamination is also more common in the higher humidity segments of a compressor system, such as receiver tanks and condensate traps.
These contaminants are removed at various stages throughout the compressor system by subsystems such as pre-filtration, condensate traps, driers, and midstream and point-of-use filters. When applying the HACCP process to a compressed air or gas system, the Critical Control Points are most commonly the point-of-use filters, as well as the condition of the point-of-use itself. As such, a risk analysis for each point of use should be performed to identify Critical Control Points. The risk analysis will also inform the monitoring criteria for each CCP, and a monitoring plan can then be developed. Once the monitoring plan is established and documented, records of monitoring the CCP according to the monitoring plan must be maintained. A summary of the FDA guidance for filtration, as well as guidance or compliance requirements from other regulatory bodies can be found here. Some best practices guidelines for microbial contamination can be found here.
Testing your compressed air and gas:
Many different options exist for testing a compressed air or gas system exist. These range from expensive in-line instrumentation to relatively cheap single use detector tubes and impactors. However, testing a system in-house opens a whole range of liability and potential hang-ups. Furthermore, any testing done will require quality control and calibration of the testing apparatus.
Accredited laboratories offer a measure of confidence and simplicity at cost-effective prices to help ensure continuing FSMA compliance. Accreditation to ISO 17025 guarantees appropriate handling and analysis of test items and ensures accuracy and consistency. Trace Analytics ups the ante by providing education and resources to allow operators to make intelligent and confident decisions regarding the scope and criteria for monitoring of their compressed air and gas CCPs. Our analysis reports provide easily referenced documentation of monitoring. Training resources are provided to ensure our customer’s ability to fulfill FSMA training and competency requirements. Our HACCP trained customer service team and long experience in the compressed gas industry are powerful tools for our customers, regardless of whether they are new to HACCP, or seasoned veterans.
Matthew DeVay has over 10 years of experience in Quality Assurance and chemical testing. As the Quality Assurance Director for Trace Analytics, LLC, he oversees and directs compressed air analysis and has helped countless customers successfully troubleshoot compressed air systems. He is a member of the Medical Gas Professional Healthcare Organization, and an expert in GC and GC/MS analysis.
Trace Analytics is an A2LA accredited laboratory specializing in compressed air and gas testing for food and beverage manufacturing facilities. Using ISO 8573 sampling and analytical methods, their laboratory tests for particles (0.5-5 microns), water, oil aerosol, oil vapor, and microbial contaminants found in compressed air. For over 29 years, they’ve upheld the highest industry standards of health and safety, delivering uncompromising quality worldwide in accordance with ISO, SQF, BRC, and FDA requirements.
Links and Resources:
Trace Analytics Resources
- The Seven Principles of HACCP Application: Compressed Air Systems - https://www.airchecklab.com/manufacturing/the-seven-principles-of-haccp-application-compressed-air-systems/
- HACCP and Compressed Air Testing - https://www.airchecklab.com/news/haccp-and-compressed-air-testing/
- Compressed Air System Risk Assessment: Do I Need to Test? - https://www.airchecklab.com/food/compressed-air-system-risk-assessment-do-i-need-to-test/
- Sampling Plans for GFDI-Required Compressed Air Monitoring - https://www.airchecklab.com/manufacturing/sampling-plans-for-gfsi-required-compressed-air-monitoring/
- Food Safety Management Systems: Who Regulates Compressed Air? - https://www.airchecklab.com/food/food-safety-management-systems-who-regulates-compressed-air/
- Our Compressed Air – Food Grade Air in Manufacturing - https://www.airchecklab.com/services/manufacturing-iso-8573-1/food-grade-air/
- FSMA - https://www.fda.gov/Food/GuidanceRegulation/FSMA/
- FSMA – Final Rule for Preventative Controls for Human Food https://www.fda.gov/Food/GuidanceRegulation/FSMA/ucm334115.htm
- Lists “Upcoming Compliance Dates”
- Managing Food Safety: A Manual for the Voluntary Use of HACCP Principles for Operators of Food Service and Retail Establishments - https://www.fda.gov/Food/GuidanceRegulation/HACCP/ucm2006811.htm
- DSMA Preventative Standards - https://www.fda.gov/Food/GuidanceRegulation/FSMA/ucm256826.htm
- Preventative controls plan is required
- CFR- Code of Federal Regulations Title 21 (references compressed air) https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=111.27
- FSMA Guidance Documents - https://www.fda.gov/Food/GuidanceRegulation/FSMA/ucm253380.htm#guidance
- Micro - https://www.fda.gov/food/guidanceregulation/ucm064458.htm
- HACCP – GMPs – Parker reference - https://www.foodengineeringmag.com/ext/resources/WhitePapers/Compressed-Air-for-Food-GMPs.pdf
- Compressed Air GMPs for GFDI Food Safety Compliance – Parker CABP article - https://www.airbestpractices.com/standards/food-grade-air/compressed-air-gmps-gfsi-food-safety-compliance
- Jun 29 2020 06:01 PM
- by Simon
Air quality is mentioned throughout the SQF Code Edition 7.2, in which we are given the guideline: “compressed air used in the manufacturing process and in direct contact with food products, primary packaging, or food contact surfaces, is clean and presents no risk to food safety and that it shall be regularly monitored for purity.” In this case, purity can be understood as “the absence of contaminants that could cause a food safety hazard.” 
SQF also states that, “food processing facilities need to operate from a fundamental assumption that compressed air can be a source of chemical and microbiological contamination.”  Similarly, BRC Global Standard for Food Safety Issue 7, Clause 4.5.4 states that, “Air, other gases and steam used directly in contact with, or as an ingredient in products shall be monitored to ensure this does not represent a contamination risk. Compressed air used directly in contact with the product shall be filtered.” 
What are the potential contaminants in compressed air at your facility? Take a look at the first article in this series titled Compressed Air Contaminants where we identify particles, water, oil aerosol, oil vapor, and microorganisms to be potential risks. Now we will turn our attention on how to sample for particles, water, and oil contaminants. Microorganisms will be covered in a future article. You can also view a recorded webinar on food grade air entitled Navigating the Path to Food Grade Compressed Air Quality at IFSQN.com.
Where to Sample
SQF recommends (in their FAQs) using 0.1um (micron) particle filters or as needed based on a risk analysis. We recommend that you take air samples after point-of-use (POU) filters if you have any installed. Your service distributor or trained maintenance staff should prepare the sampling ports. Setting up a sampling port can be as simple as adapting the pipe or tubing with the correct fittings. However, in some cases, you may need to break into the line to establish the necessary connections. Fully purge the system, as tapping into the distribution line may loosen rusty particles that can break loose from within the pipe. This is also true of metal or plastic shavings from newly threaded pipe, or sealing material.
Establishing a Monitoring Plan
Ultimately, the purpose of any monitoring program is to verify that your compressed air quality is in a state of control and will not contaminate your product. As you probably know, the compressed air system pulls ambient air in through the intake and compresses it for process use. What you may not know is that typical ambient air contains millions of inert particles, 5-25 grams of water, 1-5 micrograms of oil, and tens to hundreds of bacteria per cubic meter. The odds of contamination entering your system are against you from the beginning.
No single monitoring plan exists for all manufacturers. We recommend performing a risk assessment to identify your specific areas of concern and to determine what to test for, frequency of testing, number of sampling points and ultimately, the acceptable purity limits.
Another method used to determine these factors is the performance of baseline analyses. We recommend testing for particles, water, and oil using ISO 8573-1:2010 purity limits at various points throughout your facility. The analytical laboratory classifies your compressed air quality according to the ISO 8573 purity classes. This allows you to verify that the quality of air matches the type of filtration installed at your facility. With sufficient data points, a trend analysis can be performed to make an educated decision on whether the air quality is acceptable for all product lines or if improvements are necessary to ensure food safety.
An excellent source of information is the Food and Beverage Grade Compressed Air Best Practice Guideline 102  from the British Compressed Air Society (BCAS). It recommends testing at least semi-annually, unless otherwise determined by the HACCP process or manufacturers’ recommendations. If an alteration to the design or distribution piping is made, or maintenance is performed that could affect the quality of the air, then additional testing should be performed. For air that comes in direct contact with the product, they recommend ISO 8573-1:2010 [2:2:1], and for indirect contact, purity classes [2:4:2]. (Note the order of the purity classes are always [Particles:Water:Oil] or [P:W:O].)
When selecting a laboratory to provide your compressed air quality assessments make certain that you are getting what you pay for. According to the FDA(4) “Valid analytical results are essential to make informed decisions that impact public health. At its heart, laboratory accreditation is about laboratories’ consistently producing valid results by focusing on assuring 1) management requirements for the operation and effectiveness of the quality management system within the laboratory and 2) technical requirements that address the correctness and reliability of the tests and calibrations performed in laboratory.”
For purity classes 1-5, particles are measured by their size and quantity. ISO 8573-1 establishes three particle size ranges: 0.1 to 0.5 um (microns), 0.5 to 1.0 um, and 1.0 to 5.0 um. Also, there can be no particles greater than 5 um present to qualify for a class 1-5 purity rating. Only purity classes 1 and 2 require all three size ranges. Typically, compressor or filter manufacturers recommend filters for particle and oil removal to meet class 1 or 2 for the food industry.
To measure particles as small as 0.1 um, a calibrated laser particle counter (LPC) is required. For many food manufacturers, this may prove to be impractical due to the availability and expense. While LPCs can be costly if only a few samples are to be taken on an infrequent basis, an LPC is extremely helpful when a particle contamination problem exists. The laser particle counter can be used to rapidly sample multiple locations with on-site test results, and is therefore ideal for troubleshooting. The use of an LPC has played a crucial role in identifying the source of particle contamination from a variety of sources at some of our customers’ facilities. Contamination has been detected from O-rings in valves and filter housings, flexible tubing, distribution piping, and plastic or metal fittings.
On the other hand, particles sized at 0.5 um and larger can be sampled easily and at a significantly lower cost. This is accomplished by using a filter membrane inside a filter housing and passing a known volume of the compressed air over the membrane. Samples are lightweight and easily transportable worldwide, and analyzed using an optical microscope.
For purity classes 6, 7 and X, particles are measured by weight only. These classes are most often used for industrial tools and pneumatically operated machines with filtration by general-purpose filters. Commonly, class 6 limit of 5 mg/m3 is the maximum allowable limit for breathing air used by sport and commercial divers in the U.S. No particle size or quantity is included in these classes. Instead, results are reported by mass weight in mg/m3. Analyses are performed using a calibrated micro-balance. Classes 6, 7, and X are not typically considered food grade air quality by filter or compressor manufacturers.
Trace Analytics offers the LPC Rental Program for our US customers. 
Photo credit: Trace Analytics, LLC
Common Sources of Particle Failure
A common error identified through a monitoring program is the installation of inappropriate tubing or piping after a point-of-use filter. Even a short, brand new, 2-foot length of galvanized piping can be the source of particle contamination.
When the more stringent class 1 particle limit is required (more common in pharmaceutical or electronics) it becomes critical to limit or eliminate the use of quick disconnect fittings, valves, gauges or anything with O-rings because they can lead to sporadic particulate contamination. When a sample is taken from an outlet, it is important to ensure that the sampling process itself isn’t contributing to contamination. The connection between the point of use and the sampling equipment should be short, straight, and preferably made of stainless steel. There should be no elbows, tees, valves or dead ends.
In some cases, where stainless steel piping cannot be used, flexible tubing with low particle shedding properties must be used. Recommended tubing material types, in order of preference, include: stainless steel, conductive polymer, polyester, vinyl (if plasticizer does not interfere), polyethylene, copper, Teflon, and aluminum. 
Water Vapor Testing
There are several ways to measure dew point in compressed air. There are in-line instruments or sensors that provide constant measurements, can transmit data, and/or alarm when results are outside of the required parameters. There are also portable devices that can be used to confirm that the water vapor is in the proper range at use points.
It is important to follow the manufacturer’s recommendations and calibrate the equipment/sensors to assure consistency of results. Another quick and inexpensive method for water vapor determination are length-of-stain (detector) tubes. They are a portable method for determining water vapor for both refrigerated and desiccant dryers. Typically, these require a known quantity of compressed air to flow through the tube at a specific flow rate. A chemical reaction occurs between the water vapor in the sample and the chemicals in the tube. This will be represented by a length of color stain on the tube. Sampling times vary between 2.5 and 12.5 minutes—depending on a variety of factors.
AirCheck Kit K8573NB sampling for water as shown.
Photo Credit: Trace Analytics, LLC
Water Sampling Tips
To prevent the interference of ambient moisture permeating into the compressed air sample stream, select impermeable materials, such as polished stainless steel or PTFE (best known brand is Teflon) . Avoid using hygroscopic materials like rubber, as these materials can allow ambient moisture to permeate into the tubing and affect the results. The use of polished or electro-polished stainless steel is important to prevent any water from collecting on the inner surface of the sampling apparatus.
Any type of connection between the sampling apparatus and the sampling outlet should be short, straight and without dead ends. Avoid the potential for leaks by limiting elbows, tees, and valves.
Total Oil Testing
The terminology used to describe oil can be quite confusing. It is important to understand which form of oil will be tested. Some common terms for oil include: condensed hydrocarbons, oil mist, oil aerosol (these are all aerosols), oil vapor, total gaseous hydrocarbons, and total volatile hydrocarbons (these are all gaseous). Aerosols are usually reported in milligrams per cubic meter (mg/m3) while oil vapors are often noted in parts per million (ppm). ISO 8573 specifies sampling for oil aerosol and oil vapor separately, then combining test results to comply with Total Oil limits for class 1 and 2. Results are reported in mg/m3. Critical control points should be monitored for both oil aerosol and oil vapor for better quality control. This is one of many reasons why testing to ISO 8573 purity classes makes sense for the food manufacturer.
ISO 8573 has a few definitions that help clarify which hydrocarbons are to be tested:
- Oil: A mixture of hydrocarbons composed of six or more carbon atoms (C6+)
- Oil Aerosol: A mixture of liquid oil suspended in a gaseous medium having negligible fall velocity/settling velocity
- Organic Solvent: A mixture of or a combination of the following identified groups: alcohols, halogenic hydrocarbons, esters, esters/ether alcohols, ketones, and aromatic/aliphatic hydrocarbons
- Wall Flow: The proportion of liquid contamination no longer suspended within the air flow of the pipe
Oil Aerosol Testing
A common method for collecting oil aerosols for laboratory analysis is by passing a known volume of air across a pre-weighed filter membrane. The sample can then be analyzed by either infrared spectrometry or gravimetrically.
The path from the point of use to the collection method should be kept short, without bends or drops to avoid the loss of aerosols. The use of cylinders (without a filter membrane) to collect oil aerosols is not recommended because if oil aerosols are present they will adhere to the sides of the cylinder wall.
Oil Vapor and Organic Solvent Content Testing
Oil vapor analysis is suggested for the food industry and required by ISO 8573 for classes 1 and 2. To accomplish analysis for oil vapor consisting of hydrocarbons with six or more carbon atoms (C6+), a charcoal tube must be used to collect the sample. A known volume of air is passed through the collection tube. The sample is lightweight and can be easily shipped to a laboratory for analysis by gas chromatography.
Lighter hydrocarbons composed of five or less carbon atoms are not included in total oil purity classes. These lighter hydrocarbons—as well as other gases like carbon monoxide, carbon dioxide, sulfur dioxide and nitrogen dioxide—are addressed in section 8573-6 Gaseous Contaminant Content. There are no established ISO 8573 purity classes or limits for these other gases. Trace Analytics offers methods to collect the C5- hydrocarbons and other gases upon request.
Common Sources of Oil Failure
Clean, oil-free fittings are critical for a true reading of contamination. Oil aerosol and vapor are detected at very low levels. A slight amount of hydrocarbon contamination in a fitting is enough to produce unacceptably high levels of oil vapor (OV).
The filter cassette holds three layers of membranes for oil aerosol collection, and the charcoal tube collects oil vapors.
Photo Credit: Trace Analytics, LLC
Solvents remain trapped in O-rings and fittings for a long time. Because of this, only solvents that are not C6+ hydrocarbons should be used. Many common cleaning agents are high in C6+ hydrocarbons. Research the solvents you use in your manufacturing area. Ensure that the air compressor inlet is not situated near a source of C6+ materials. This would include cleaning baths, solvent waste cans, process solvents, or other ambient sources of hydrocarbons such as forklift exhaust.
If contamination is expected in the ambient or process air, have the laboratory perform oil vapor (OV) analyses using gas chromatography/mass spectrometry (GC-MS), a technique that readily discerns between OV and other compounds. These other compounds can be reported separately, thus not impacting the OV level as might occur with gas chromatography with a non-specific detector, such as flame ionization detection (FID).
ISO 8573-1:2010 purity classes serve as the foundation for compressed air monitoring to meet certification requirements. As an internationally accepted standard, ISO 8573-1 is a common language available to the food manufacturer, compressed air system supplier, and testing laboratory.
 SQF Code Edition 7.2, http://www.sqfi.com/...code/downloads/
 SQF FAQs, http://www.sqfi.com/...f/faq/sqf-code/
 BRC Global Standard for Food Safety Issue 7, http://www.brcbooksh...378/food-safety
 U.S. Food and Drug Administration, Frequently Asked Questions on FSMA, http://www.fda.gov/F...b_Accreditation
 Particle Measuring Systems, Inc., Basic Guide to Particle Counters and Particle Counting, http://www.pmeasuring.com
 ISO 8573 specifications referenced above are copyrighted and are available for purchase online at http://webstore.ansi.org/.
Ruby Ochoa, President and Co-Owner at Trace Analytics LLC
Ruby has over 30 years of experience in compressed air and gas quality testing. Demand from customers influenced Ruby and co-owner Richard A. Smith into finding a solution for manufacturers needing affordable ISO 8573 testing. Trace Analytics developed the AirCheck Kit™ Model K8573NB specifically to address the needs of today’s manufacturer. The kit captures samples for particles (0.5-5 microns), water, oil aerosol and oil vapor. All samples must be submitted to Trace’s A2LA accredited laboratory for analysis. Trace’s lab accreditation meets ISO/IEC 17025 criteria as established by FSMA. For more information, contact Ruby Ochoa, tel: (512) 263-0000 ext. 211, email: Ruby@AirCheckLab.com, or visit AirCheckLab.com.
See the interview where Ruby answers your questions about major contaminants on “Ask the Expert"
- Jun 29 2020 07:08 PM
- by Simon
- The 7.2nd edition of the SQF Code states:
- “Compressed air used in the manufacturing process shall be clean and present no risk to food safety.”
- “Compressed air used in the manufacturing process shall be regularly monitored for purity.”
- The 7th issue of the BRC Global Standard for Food Safety states:
- “Air, other gases and steam used directly in contact with, or as an ingredient in, products shall be monitored to ensure this does not represent a contamination risk. Compressed air used directly in contact with the product shall be filtered.”
- The 5th issue of the BRC Global Standard for Packaging and Packaging Materials states:
- “Based on risk assessment, the microbiological and chemical quality of water, steam, ice, air, compressed air or other gases which come into direct contact with packaging shall be regularly monitored.”
In the SQF Frequently Asked Questions on their website they state that:
“Food processing facilities need to operate from a fundamental assumption that compressed air can be a source of chemical and microbiological contamination. The site must verify and validate that the compressed air used in the facility is appropriate for use and not a source of contamination.”
With this background set, let’s explore the nature of compressed air contaminants.
Experts like the Compressed Air & Gas Institute (CAGI) and the International Organization for Standardization (ISO) agree that the primary contaminants to monitor are particles, water, and oil (PWO). CAGI also includes micro-organisms in this list. ISO 8573-1:2010 establishes a variety of purity classes for PWO from very clean [1:1:1] to shop air [6:7:X]. These classes are different from air quality specifications for breathing air used by firefighters and divers. ISO 8573-1 focuses on quantifying particles by size, and oil aerosol and oil vapors consisting of hydrocarbons with 6 or more carbons in the chain (C6+).
Breathing air specifications primarily focus on gaseous contaminants like oxygen, nitrogen, carbon monoxide, carbon dioxide, total gaseous hydrocarbons (C1-C10), and oil aerosol. Both ISO 8573-1 and common breathing air specifications provide a variety of limits for water content depending on the usage.
ISO 8573-1 does not have purity classes for other gaseous contaminants but stipulates that if these are a risk for a particular application, they should be monitored.
We can safely generalize that an excess amount of particles, water, oil aerosols, oil vapors, and micro-organisms are contaminants that can affect the quality and safety of most foods. Gaseous contaminants listed in ISO 8573-6 are EPA cited environmental pollutants such as carbon monoxide, carbon dioxide, hydrocarbons C1-C5, nitrogen oxides, and sulfur dioxide. If the food manufacturer determines that these or other gases can adversely affect their product, then limits should be established and air monitoring should include the specific gas(es).
Sources of Contamination
The primary sources of contamination in a compressed air supply include the intake air quality and the compressor itself. Other significant sources include distribution piping, storage receivers, and point-of-use items such as valves, gauges, flexible tubing, and fittings.
The decision about where the intake of the compressor should be located was made at installation. It is prudent to inspect the intake location to verify that air quality conditions have not changed since installation. At any given time the atmospheric air feeding the compressor inlet can have contaminants such as particles (both viable and nonviable), water vapor, oil vapor, and other gases. Careful consideration should be given to the placement of the compressor intake to avoid these contaminants as much as possible. The intake filter as a first defense should be routinely replaced according to the manufacturer’s guidelines.
The intake filter is responsible for removing particles greater than 2.5 microns in size that include solid and liquid aerosols from the outdoor environment and from within the manufacturing facility.
Atmospheric air contains aerosols of various types and concentrations, including quantities of:
• natural inorganic materials: fine dust, sea salt, water droplets.;
• natural organic materials: smoke, pollen, spores, bacteria;
• anthropogenic products of combustion such as: smoke, ashes or dusts; and
• urban ecosystem products: dust, cigarette smoke, aerosol spray cans, car exhaust soot.
Particles – Air pollution is not only a public health and environmental problem, it also contributes contamination in the form of millions of particles per cubic meter. These particles consist of acids (nitrates and sulfates), organic chemicals, metals, and soil or dust particles. Coarse particles are between 2.5 microns and 10 microns in diameter. The finer particles with a diameter of 2.5 microns or smaller are not removed by the intake filter and enter into the compressed air system.
Nonviable particles or micro-organisms such as bacteria and viruses exist in the ambient air and can enter the compressed air system through the intake. The growth of microbes are inhibited when the pressure dewpoint is -26°C / -15°F or better. A refrigerated dryer cannot provide this level of dryness and thus these systems may be more susceptible to microbial growth. It is important to note that although a desiccant dryer can inhibit growth of micro-organisms, it does not kill the microbes. Once the microbes are introduced into a warmer and wetter environment, if present, they will begin to grow again.
The compressor can contribute wear particles from its operation. Wear particles can be metallic or polymeric. Particles can also be generated from a compressed air system that utilizes a refrigerated dryer and iron piping or iron receivers. The combination of water and iron will form rust and pipe scale. Viable particles (micro-organisms) can also grow in this warm, dark, nutrient rich environment. Aluminum piping is a source for fine dust in the form of aluminum oxide.
There seems to be a general agreement that stainless steel along with certain specially manufactured polymers can form a good backbone for the transport of compressed air. Unions and valving of the piping system are critical in that material used for seals can shed particles and have a tremendous negative impact on air quality.
Photo credit: Vaxomatic
Water – Atmospheric air typically contains 1,000-50,000 ppm of water depending on where you live. If left untreated, compressed air with high levels of water is unacceptable for critical applications.
Excess water will cause corrosion in iron piping and storage receivers that can damage equipment used in your production lines and contaminate the final product.
Drops and dead ends in the distribution piping can trap water and create an environment for microbial growth.
Pressure and temperature affect the amount of water in a compressed air system.
Not only can water, the universal solvent, wreak havoc on the piping system, but in a water saturated system, aerosol can be generated from water collected on piping walls and mist the final product.
Oil – Atmospheric air typically contains between 0.05 mg/m3 and 0.5mg/m3 of oil vapor. Common sources are vehicle or motor exhaust and industrial processes.
As oil is comprised not only of liquid and aerosol, but also vapor, the cast of usual suspects is widened to include off-gassing of the more volatile compounds associated with oil, such as solvents used to clean piping and threads and glue used to cement connections. While many of these compounds may not be considered oil in the wider context, the ISO 17025 definition includes C6+ compounds and some of these are indistinguishable from oil components.
Oil lubricated compressors by the nature of their operation introduce liquid oil, oil aerosols and oil vapor from the compression process. However, using an oil-free compressor does not guarantee oil-free air as oil vapors can be drawn in through the compressor intake.
Hydrocarbons and oil (as well as particles) can be introduced by the installation of inappropriate piping. The inside of the distribution piping should be clean, oil-free with low particle shedding properties.
Other – Potential air quality problems can also arise from compressor misuse or mishandling, inattention to maintenance, and of course human error.
The use of flexible tubing should be carefully considered as many types of commonly used polymer tubing in the food industry can shed significant particles. They can also allow ambient water vapor to diffuse into the tubing. This can adversely affect the quality of dry air by raising the vapor levels. There are suitable types of tubing that are designed to have little to no particle shedding or permeability issues. Manufacturers label these types of tubing in a variety of ways.
The proper selection, sizing, and maintenance of compressors and purification packages can eliminate the threat that these major contaminants can pose to your final product. If the food manufacturer must verify the absence of contaminants such as particles, water, oil, and micro-organisms; it must do so by establishing a robust sampling strategy to assure that compressed air is in a state of constant control and will not contaminate the final product.
Ruby Ochoa, President and Co-Owner at Trace Analytics LLC
Ruby has over 30 years of experience in compressed air and gas quality testing. Demand from her customers persuaded Ruby to find a solution for manufacturers needing affordable ISO 8573 testing. Trace Analytics developed the AirCheck Kit™ Model K8573NB specifically to address the needs of today’s manufacturer. The kit captures samples for particles (0.5-5 microns), water, oil aerosol and oil vapor. All samples must be submitted to Trace’s A2LA accredited laboratory for analysis. Trace offers additional samplers and methods for analyzing contaminants outside of the above-mentioned parameters. For more information, contact Ruby Ochoa, tel: (512) 263-0000 ext. 4, email: CDATest@AirCheckLab.com, or visit AirCheckLab.com.
Have questions about contaminants in compressed air?
Submit them to TraceAnalytics@AirCheckLab.com.
Ruby will answer your questions on an upcoming segment of “Ask the Expert". Stay tuned for more details.
- Jun 29 2020 06:57 PM
- by Simon
- The 7.2nd edition of the SQF Code states: