An air impaction microbial assessment of your air supply may indicate you have unwanted inhabitants in your compressed air system.

INTRODUCTION
Manufacturers of medical devices who label their product as “sterile” may use compressed air in various applications. Applications include injection molding, operation of conveyor belts, and/or aseptic cleaning processes. The manufacturer may use these systems on a continuous basis or on an as-neededbasis.

The manufacturer may not realize that the compressed air system could be harboring microorganisms. When the air supply system is operating, it may unleash contaminants which could adversely affect the product, including operational characteristics,by compromising sterile claims, or product aesthetics.

The condition or the quality of the supplied air, from a microbiological standpoint, may not be obvious unless microbiological testing is performed. A simple air impaction microbial assay of compressed air lines, however, will alert the manufacturer to the various types of viable microorganisms that might be present.

Manufacturers of medical devices, pharmaceutical operations, or those classified as sterile fill, are constantly assessing the environmental impact on the product during the manufacturing process. This assessment usually includes the facility, the equipment, and the personnel involved in the assembly process. Sampling may include, but is not limited to, surface sampling, particulate counts, water analysis, and product testing. However, compressed air can easily be overlooked if not initially inserted into the environmental monitoring protocol or identified by an experienced environmental scientist.

The engineering department may design the facility whereby the air compressor is segregated from the area where the product is assembled for logical hygienic reasons. However, this segregation may lead to a false sense of security because it is possible that the environmental air source that feeds into the compressor may contain biological flora similar to that of the manufacturing environment. It could be possibly even higher in microbiological levels if the location of the air compressor is less controlled than that of the manufacturing environment. If the compressed air supply is not properly engineered with filters, dryers, and appropriate gauges, these microbiological inhabitants could eventuallyreach the product.

Compressor as the Culprit
The compressor itself can function as the culprit by creating a contaminated environment for the product. For example; the compressor’s pre-filters can become overloaded with dust and lint, causing the filter to cease functioning properly, thereby resulting in migration and potential strike-through. Also, there may be a contaminant in the environment which is smaller than the poresize of the pre-filter. Again, this may lead to the inefficiency of the pre-filter.

Microorganisms

A microorganism that is capable of forming a viable colony forming unit (CFU) and which exists within the compressed air line system is called the microbiological particle (MP) as per ISO 8573-4:2001(E). The microbial load on a product is referred to as Bioburden, as per ANSI/AAMI/ISO 11737. The Bioburden can come from various sources, such as human contact, air conditioning systems, the manufacturing process itself, raw materials, and any other vector that the product is exposed to. However, the least likely considered vector for contamination is the compressed air system. Maybe this is because the compressed air network is considered to be a closed system, under high pressure (usually 160 pounds of pressure and greater) and is expected to supply continuous high quality filtered air.