Testing for micro-organisms in compressed air

The Safe Quality Food Institute (SQFI) has introduced a new Safe Quality Food Manual (ISO 22000) in the U.S. According to the standard, food processors must test annually for factors including particulate, water, oil, microbiologicals and relevant gases, and ensure their compressed air system meets the appropriate quality standard.

If you are a food or beverage processor, this should raise a fundamental question: “What’s in my compressed air?” A wide variety of contaminants can end up in compressed air, with most falling into one of these groups:

Hydrocarbons
Viruses
Bacteria
Moisture (liquid water or water vapor)
Oil
Solid particles (whatever makes it past intake filter)

Some impurities, such as lubricating oil, can also be part of the mechanics of a compressed air system. Other impurities including dust (dry or wet), water (liquid or vapor) and oils (aerosol or hydrocarbon) originate in the ambient environment, so the quality of intake air is a key factor. Whatever their source, if impurities are not effectively removed from the compressed air, they can contaminate product, impair production results, increase costs and damage your reputation.

ISO 8573
As a food and beverage processor, you are now required to evaluate the purity of your compressed air against a recognized standard, at least annually. The most common quality standard is ISO 8573:2010. Depending on your application, the standard covers three categories of contaminants (dirt, water, oil) with ten classes of purity within each category (the lower the class, the higher the air quality). Note that a process involving compressed air may require a different purity class for each contaminant category.

For example, with dirt, Class 1 volume of air must contain less than 20,000 particles per cubic meter where particle size ranges from 0.1 to 0.5 micron; Class 2 must contain less than or equal to 400,000 particles per m3. With water impurity, Class 1 refers to a vapor pressure dew point of less or equal to -70°C/-94°F, and Class 2 refers to a vapor pressure dew point of less than or equal to -40°C/-40°F. With total oil (expressed as aerosol liquid and vapor in mg/m3) Class 1 is 0.01 and Class 2 is 0.1.

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