The general topic you mention has certainly generated greatly variable suggestions for limits for wet cleaning systems, some of which are accumulated in this thread – http://www.ifsqn.com...?showtopic=9365
A similar logic for both wet and dry cleaning has been adopted by NZFA based on operational criteria, an extract follows for dry cleaning -
13.6.4 Cleaning frequency
18.104.22.168 The frequency of cleaning shall be determined from a microbiological evaluation of the types of raw materials used, the characteristics of the process and the nature of the food soils and the environmental residues.
22.214.171.124 Microbiological monitoring shall be carried out according to the principles set out in Section 13.4.1.
126.96.36.199 The numbers of micro-organisms on food contact surfaces should not exceed in-house base levels that have been established for the indicator organisms, see also Section 13.4.2.
13.4.1 General requirements
Microbiological monitoring of the processing environment and food contact surfaces of plant and equipment shall be carried out to verify the effectiveness of the cleaning programme.
188.8.131.52 Indicator organisms
a. The programme shall include the surveillance of aerobic plate counts using methods generally recommended for microbiological surveillance of the environment.
A reference database, compiled using the principles of microbiological monitoring outlined in IS8/IAS8: Appendix A, should be maintained from the quantitative data.
b. Rapid tests for hygiene evaluation, e.g. bioluminescence, may be routinely used provided the methods are adequately calibrated against quantitative aerobic plate count data.
The programme shall establish a specific pathogen profile where there is a likelihood for a particular environmental pathogen to create an adverse food safety outcome in a specific product, e.g. Listeria monocytogenes in cooked ready to eat foods.
13.4.2 Performance standards
The microbiological condition of any food contact surface during operations, as measured by the mean log10 count of the indicator organism(s), should not exceed the expected mean log10 count of similar indicator organism(s) on product.
The numbers of micro-organisms on food surfaces throughout a processing day will be influenced by cleaning programmes, incoming microbial loads on the food and the opportunities for growth during production. The objective of this standard is to minimise contamination of foods through redistribution of micro-organisms from food surfaces.
The above approach conveniently reflects their believed variability and passes the responsibilty for evaluation back to the user. Not sure what level of agreement exists on this style as compared to specifying “just cleaned” surface data / limits which seem to hv an equal degree of variability also.
Personally, hv never had an auditor object to the use of in-house formats validated as “based on” appropriate (named) published refs like in the top thread. Obviously some practical data is also required. I guess this follows yr current method where 100 colonies refers to some area of surface.
An example of the practical implementation of a (presumably wet) pre-operational cleaning approach is given in ScheduleC in this link –
I realise this still doesn’t answer yr specific request for “dry’ limits. Not seen any on the IT as yet. Maybe there are some other dry process people here ?
Rgds / Charles.C
added - I know it's not directly comparable however you might find this generic (dry) validation SOP for cleaning in the pharmacological business of some interest, particularly the closing section.