The demand for sterile compressed air increases with the adoption of advanced technologies which were unknown a few years ago. The selection of a sterilization filter for a compressed air system can be a difficult task. The production of proteins, vaccines, antibodies, hormones, vitamins and enzymes involves high technology processes which require aseptic and sterile supplies of gases or liquids throughout the manufacturing cycle. The production and packaging of many dairy and food products such as beer, yoghurt, cream and cheese use compressed air or carbon dioxide. The nature of these products makes them susceptible to contamination by micro-organisms held in the compressed air or gas.

Any product that can be contaminated by airborne bacteria must be protected. In the case of food and chemicals produced by fermentation, bacteria would cause serious defects and rejection of the product.

In the fermentation and pharmaceutical industries, compressed air and other gases are used through every stage of the production process from the refining of the raw material to the manufacturing and packaging. Compressed air may be used as a source of energy in a process or as a biomedical aid. Air motors are used for explosion-free mixing of powders, instrumentation and cylinders for the batching of materials.

Process air can be used for aeration of liquids, seed fermentation and laboratory applications. Mixing air into the preparatory chemicals or the final product means that they must be as clean and sterile as the material it serves, so there can be no risk of fouling by solids, liquids or micro-organisms.

Micro-organisms are extremely small and include bacteria, viruses, yeasts, fungus spores and bacteriophages. Bacteria can be from 0.2 micron to 4 micron, viruses less than 0.3 micron and bacteriophages down to 0.04 micron. The sterilization filters that have to cope with these organisms have to have a performance rather better than these dimensions. The presence of these living organisms can be a serious problem in process industries, because they are able to multiply in the right conditions.