The most effective line of defense against food contamination caused by compressed air is point of use filtration. Even the best compressor room system filtration does not eliminate harborage sites and biofilm buildup in the downstream compressed air piping system. For additional information on contaminants present in compressed air, see the diagram in part 3 of this series.
Best practice: Good manufacturing practice (GMP) system design – point of use filtration
Wherever compressed air comes in contact with food, either directly or indirectly, the following three stages of filtration will significantly reduce the risk of microbial contamination of the food.
- Stage 1: Remove bulk liquid and particulate matter down to 0.01micron at greater than or equal to 93% DOP efficiency (as measured by the Dioctylphthalate Fog Method test, MIL-STD-282; method 102.9.1). Filter should include an automatic drain.
- Stage 2: Remove oil and water aerosols and smaller particulate matter down to 0.01 micron at greater than or equal to 99.99% DOP efficiency. Filter should include an automatic drain.
- Stage 3: Remove microbial contamination down to 0.01 micron at greater than or equal to 99.9999% DOP efficiency with a sterile air filter.
Best practice: Sanitation Standard Operating Procedures (SSOP) – filter maintenance
- Stages 1 and 2 (Coalescing filtration): Change the filter element every six to twelve months.
- Stage 3 (Sterile Air filtration): Change the filter element every three to six months, as necessary based on point of use air quality test for microbial content.
Optional: Steam sterilize stage three, providing the filter is designed for CIP (Clean in Place) sterilization. Follow manufacturer’s instructions.
Note: Sterile air filters are designed to capture microbial matter larger than the nominal element rating, so microbial matter will not create a differential in pressure across the element. Therefore, measuring differential pressure across the element will not give an accurate reading of contamination. Air testing and/or regularly scheduled element changes are the best practice.
SQF (Safe Quality Food) Code Requirements:
The 7th edition, published July 2012, has added the following verbiage to Module 11: Good Manufacturing Practices for Processing of Food Products:
11.5.7 Air Quality
- 126.96.36.199 - Compressed air used in the manufacturing process shall be clean and present no risk to food safety.
- 188.8.131.52 - Compressed air used in the manufacturing process shall be regularly monitored for purity.
SQF Implementation Guidelines:
Where compressed air contacts the food either directly or indirectly, a point of use .01 micron filter with a 99.999% efficiency rating should be installed. Doing so will fulfill the requirements of the new 184.108.40.206.
A periodic test (based on empirically derived test intervals) to confirm the absence of contamination should be performed at all points in the system where compressed air could contact the food. This will fulfill the requirements of 220.127.116.11.
For further information, please refer to page 47 of the SQF Implementation Guidance Document.
This series was written by Lee Scott, Market Development Manager, Parker Hannifin