Health Canada Guideline
Air that comes into direct contact with primary contact surfaces and/or the product should be monitored to control the level of particulates, microbial contamination, and the absence of hydrocarbons. Limits used should take into consideration the stage of manufacture, product, etc. Additional tests might be required due to the nature of the product. Gas used in aseptic processes must be sterile and filters checked for integrity.
To verify the contents of the gas system at factories that comply with GMP, a complete gas analysis should be carried out at least once a year. This is particularly important in cases where the gas is in contact with the finished product. For example, in the GMP guide for APIs issued by the International Conference on Harmonization (ICH), Q7A -7.31 states that complete analysis should be carried out at suitable intervals (i.e. at least once a year).