HEPA filters validation

Initial validation once per HEPA filter unit Revalidation annually... 

Adjustments in the air source should be made to obtain a controlled flow of air within the tunnel and across the entrance and exit openings. Air must be particulate-free as it enters the tunnel area therefore, all high efficiency particulate air (HEPA) filters in the tunnel must be integrity tested and certified prior to validation studies. 

Gas niters may be evaluated prior to use by the same methods used for liquid filters (see Section 111 below), allowing that they can be effectively dried out and sterilized without loss of the qualities being tested. Alternatively they may be evaluated by exposure to particles in a gas stream, for instance by the sodium name test, which is also used for HEPA filters. Microbiological tests have to be considered in a somewhat different light. Leahy and Gabler 71 describe an aerosol challenge test of 10 Ps. diminuta bacteria per mL over a four-day period as an appropriate manufacturer s validation test. It would not be practical for routine use. 

Housings for terminal HEPAs should have airtight seals to the ceiling behind the grilles or diffusers. The sealing of the HEPA filter should be on the air-inlet side of front-withdrawal HEPAs and on the air-outlet side of back-wiih-drawal HEPAs. Filter housings should be equipped with an access port behind the filter to allow access of smoke for validation purposes (see below). 

The process used should include air circulation within the chamber and the maintenance of a positive pressure to prevent the entry of non-sterile air. Any air admitted should be passed through a HEPA filter. Where this process is also intended to remove pyrogens, challenge tests using endotoxins should be used as part of the validation. 

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