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Sources of Contamination in Food Grade Compressed Airfood grade compressed air compressed air testing compressed air contaminants
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.