Industrial Utility Efficiency

Compressed Air System Design Recommendations for Food Processors

Editor’s Note: This is an edited version of the previously published article, “Oil in the Sausage”, published in 2007 by the same author.


Oil in the Würstchen!

Oil in the sausageIt was the Fall of 1997 in Germany. I was just another guy working in the German compressed air industry. East Germans were still being looked down on - seven years after unification, the Euro was launching in little over a year - forcing marketing managers like me to scramble and create unified european Euro pricing strategies, European Cohesion Funds were flowing out of Germany and into the Mediterranean (not literally), and the diminutive Mercedes “Smart Car” was the cool car for space-challenged urban dwellers. With this going on, you can imagine the surprise of the compressed air industry when compressed air was featured in “Der Spiegel”, a “Newsweek-like” weekly magazine in Germany with national distribution.

“Oil in the Sausage!” hollered the article headline! It proclaimed how a consumer-packaging expert had found mineral oil in a sampling of vacuum-wrapped frankfurter würstchen packages he had tested. The resulting investigation discovered that the food packaging facility in question, did not have proper compressed air filtration systems installed. Oil vapors (hydrocarbons), present in the compressed air system, had entered the packaging machinery - which then injected them into the sausage package. The hydrocarbons condensed at a later date and were discovered by this consumer advocate product-tester.



You can imagine how the fingers started to point. The packaging machine manufacturer said it wasn’t their responsibility to provide quality compressed air-that it was the responsibility of the factory. The consumer advocate said, “Quatsch to that!” He felt that all packaging machinery manufacturers should install activated carbon filters, which remove oil vapors, on the compressed air inlet side to their machines. He found that few do. He went on to sarcastically assert that the additional \$350.00 filter on the \$150,000 packaging machine should be economically feasible, given the potential liabilities. All eyes turned to the compressed air industry for a recommendation.

The “Oil in the Sausage” story spurred a swift reaction from the German VDMA (German Engineering Federation), which issued the recommendation we will document in this article. The U.K. code of practice (put together by the British Compressed Air Society and the British Retail Consortium) is more recent and incorporates the latest ISO 8573.1 air quality classes. The objective of this article is to inform food industry compressed air users and specifiers, of the voluntary compressed air quality recommendations, provided by the compressed air industry in the U.K. and in Germany


ISO 8573.1 Compressed Air Quality Classes

Before discussing the air quality recommendations, it is useful to understand ISO 8573.1 Air Quality Classes. In the early 1990’s, the International Standards Organization (ISO) announced a very practical way for compressed air quality to be defined. The ISO 8573.1 Standard (updated in 2001) established “Quality Class Numbers” to be applied to different levels of contamination in compressed air systems. Moisture, solid particulates, and oil were identified as the primary contaminants in a compressed air system and “Quality Class” numbers were applied to them. Quality Class numbers eliminate potential confusion over Fahrenheit/Celsius conversions, mg/ppm conversions, and language translations (can you say dewpoint (drucklufttaupunkt) in German?) in a specifying situation.

An end user can simply specify ISO 8573.1 Quality Class 1.4.1 compressed air for his facility. The first digit represents Class 1 Solid Particulate Removal. The second digit represents a Class 4 Dewpoint of 3 C (38 F), and the third digit represents Class 1 Total Oil Removal of 0.01 mg/m3 (0.01 ppm). The food industry compressed air standards we will review both used ISO 8573.1 as their way to specify compressed air quality.

ISO 8573-1:2001 Compressed Air Quality Classes

Air Quality Classes


Germany’s VDMA Recommendation for the Food Industry

The VDMA (German Engineering Federation) section for the compressed air industry responded swiftly to the “Oil in the Sausage” 1997 article in Der Spiegel, with a document titled a “Recommendation for Compressed Air Quality in the Food Industry”. It used ISO 8573.1 as the method to specify air quality and it recommended the required air treatment equipment to achieve the desire air quality. It is interesting to note that the recommendation, on the front page, stated “this recommendation applies to all air compressors independent of type.” This is an obvious reference to oil-free vs. lubricated air compressors and suggests that air treatment requirements are the same for either compressor technology. For a copy of the recommendation visit

The VDMA recommendation was written in two sections:

  1. For packaging machines where compressed air is in contact with packaging material which is directly in contact with the food or drug product
  2. If the compressed air is in direct contact with the product or mixed with it

In both sections, the recommendations varied based upon the pipework. If the pipework in the facility is new or cleaned, centralized air drying and filtration systems are recommended. If the pipework is “polluted or hard-to-clean”, centralized air drying is recommend while decentralized filtration is recommended. By “centralized” the VDMA means the location of the air treatment equipment can be next to the air compressors in the “compressor room”. “Decentralized” means that the air treatment should be located on the factory floor directly upstream of the machine or process where compressed air can come into contact with food. The recommendation states that new or cleaned air pipework should be made of:

  1. Zinc-plated steel suitable for food
  2. V2A/V4A
  3. Compressed air-approved plastic
  4. Aluminum

Another installation note was that no system bypasses be used.

The recommendation calls for ISO Class 4 moisture removal equal to a 38 F (3 C) pressure dewpoint in all situations. It does state that the refrigerated air dryers should have a dewpoint alarm built into the unit. There is also a note that for direct contact applications with extremely moisture sensitive products, then Class 4 is not sufficient and a desiccant or membrane air dryers (providing Classes 1-3) should be used.

Oil removal and particulate removal are both specified as per ISO 8573.1 Air Quality Class 1. The section on “indirect contact” suggests using a 0.01 ppm coalescer followed by an activated carbon filter. The section on “direct contact” suggests using a 1 micron filter, a 0.01 ppm coalescer, and a activated carbon tower/adsorber. Sterile filtration is also recommended in all situations where seen as appropriate.


A Voluntary U.K. Code of Practice for Food Grade Air

Ham packagedSuch is the name of the code of practice jointly prepared, in 2006, by the British Retail Consortium and the British Compressed Air Society (BCAS). Mr. Greg Bordiak is the Technical Officer of the BCAS who produced the code. For more information on acquiring a copy of the code, visit This voluntary code is very complete and includes compressed air system installation requirements, compressed air quality specifications for “contact” and “non-contact” applications, and verification methods.

Within the compressed air system installation requirement section, are recommendations for air compressors. The importance of the quality of intake air is emphasized to prevent the introduction of dust, hydrocarbons, and chemical vapors into the air compressor. The importance of intake filtration (with regular maintenance) is also emphasized. The code of practice also suggests that in installations with potential contamination areas with risk, known as Critical Control Points (CCP’s), that food-grade lubricants be required if lubricated (oil-injected) air compressors are used.

The use of carbon steel pipe is discouraged as it can corrode in the presence of moisture in the compressed air. Other piping materials such as aluminum, copper, stainless steel, plastic, are encouraged. It is noted that with plastic pipe, considerations for temperature acceptance of the plastic pipe material should be made.


Bottling plant

Bottling barbeque sauce at a food processing plant


Contact is defined in the code as, “the process where compressed air is used as a part of the production and processing including packaging and transportation of safe food production.” The code of practice calls for the equivalent of ISO 8573.1 Quality Class Air 2.2.1. The “2” digit calls for a -40 C (-40 F) pressure dewpoint. This dewpoint specification therefore recommends the installation of desiccant air dryers and membrane air dryers (for lower flow volumes).

Non-contact is defined in the code as, “the process where compressed air is exhausted into the local atmosphere of the food preparation, production, processing, packaging or storage.” This application calls for the equivalent of ISO 8573.1 Quality Class Air 2.4.1. The “4” digit specifies a +3 C (38 F) pressure dewpoint – which signals the possible use of a refrigerated air dryer. Whether or not separate drying systems (desiccant and refrigerated) are practical will depend upon the characteristics of each installation. Some may find it more practical to use one desiccant air dryer for the whole installation. They should, however, be aware of the energy costs involved with desiccant air dryers vs refrigerated air dryers.

BCAS & BRC Food Grade Purity Recommendations

Food Grade Purity Recommendations

Chart provided courtesy of Parker domnick Hunter.

Particulate and oil removal filtration are specified as ISO Classes “2” and “1” respectively, for both contact and non-contact applications. This means that one micron filtration for particulates and 0.01 mg/m3 (0.01 ppm) oil coalescers and activated carbon filters will be required. Please note that the code specifies “total oil”, which therefore mandates the use of activated carbon (also known as charcoal filters) filters, which can capture oil vapors (particularly hydrocarbons).

The BCAS/BCR Code of Practice has a section dedicated to measurement and testing. This is an area of great “opportunity” in compressed air systems. This code recommends testing the installation twice per year for solid particles (dirt), humidity, total oil, and microbiological contaminants. The code suggests the appropriate ISO codes which define how to conduct the specific tests for air purity.



Lubrication Standards in the U.S.

Lubrication standards cover what lubricants an air compressor may use, in a food industry application. The United States Department of Agriculture (USDA) has requirements for the use of the designated H1, H2 and H3 lubricants. NSF (National Sanitary Foundation) also has a standard (NSF 116-2000) which follows Germany’s food grade lubricant standard DIN V 0010517, 2000-08. It is up to the factory to determine what lubricants are required in the factory. The guidelines provided by the USDA on lubricants are:

  • H1 lubricants are food-grade lubricants used in food-processing environments where there is the possibility of incidental food contact
  • H2 lubricants are nonfood-grade lubricants used on equipment and machinery where there is no possibility of contact
  • H3 lubricants are food-grade lubricants, typically edible oils, used to prevent rust on hooks, trolleys and similar equipment





The codes and recommendations put forth by the BCAS/BRC and by the VDMA provide the compressed air user and specifier in the food industry with some VOLUNTARY guidelines to consider when designing a compressed air system. The key word here is “voluntary”. These recommendations do not recommend the involvement of any inspectors or the creation of new regulations. The compressed air industry has simply shared very solid, unbiased, and practical recommendations to the food industries in their respective countries.


For more information contact Rod Smith.


To read more Compressed Air Standards articles, visit