Compressed gases are used widely in pharmaceutical production facilities. Common gases such as air and nitrogen are often injected into cleanroom environments or processes or act as barriers in the production of Active Pharmaceutical Ingredients (API). First released in 1991 and updated in 2001, ISO 8573 contains several part in maintaining a particle-free compressed gas for cleanroom environments. Compressors used in pharmaceutical applications should be 100% oil-free and manufactured to ISO 8573 Class 0 standards which must successfully pass strict testing by a qualified external laboratory. Testing for particulate contamination in compressed gases are outlined both downstream and upstream: first, removal of water vapor and particulates: testing the compressed gas line; Testing for non-viable particles using a particle counter; and lastly, testing for viable particles using an active air sampler.