For absolute filters, you should do integrity testing and for coarse filters, you should monitor differential pressure. This is actually a part of area qualification.
ASHRAE Standard 52 actually deals with the testing of common HVAC filter efficiencies.
HEPA filtration is a different matter. As best I can tell, the FDA has no specific standard that they've formulated themselves (not surprising). The HEPA standard is based on a 3 micron particle effectiveness. That is the worst case size. Particles larger and smaller will be easier to block with HEPA. ULPA filtration ratchets up the decimal point effectiveness after the first 99.9...%.
IEST establishes clean room particle counts, NSF for BSC's, and there is also some LLNL field-testing standards for nuclear applications - although those would probably work for any situation. A special trace gas is used in conjunction with a particle counter. The particle counter itself is an extremely expensive instrument. Many companies purchase the service, instead, and there are some well-known laboratory testing firms that can perform the certification.
I believe all of these standards are also traceable back to an ANSI and ISO standard as well.
I consider 3micron is a typo as it is 0.3micron. Actually, MPPS (most penetrating particle size) falls in the range of 0.1 to 0.5 microns and 0.3 micron size is selected as an average.
We need not do periodical testing of efficiency of filters as this needs bulky setup and this is a destructive testing. We have to have manufacurer's certificate for efficiency and then do the integrity testing periodically. Interestingly, FDA doesn't even specify what type of filter is to be used for various classes. I have seen class 100000 areas being maintained with EU-8 (>95% at 0.5micron) in plenum, terminal EU-12(>99.97% at 0.3micron) and EU-13 (>99.997% at 0.3 micron) as well. It all depends upon the designer's ability(?) to take risk.
ISO 14644-3 specifies methods to leak check the filters. But IES-RP-CC1 and IES-RP-CC6 are good references.
Though Pharma Industry follows a strict 6 month period for HEPA integrity testing, regulators, sometimes, ask for retrospective data about filter integrity(or cleanliness data of the controlled space). This is to take care of the cleanliness during the 6 month period during which the filters are not checked. Of late, continuous monitoring of particles is in vogue, particularly for liquid paranterals.
Yes, you are correct - 0.3 micron is MPPS. For the rest, we are in agreement. The point being, FDA does not appear to generate its own specific standard (neither CDC nor NIH), and testing/validation is not something typically done by the owner. If HEPA filtration is deemed necessary, then the specific filters are certified (and tested) by the mfr. Clean room particle counts are made and certified, but typically, that is part of new construction and is for the purpose of validating the design.
That does not preclude the need to have the capability for isolated circumstances. Health and Safety Engineers may need to have that skill for unique situations and/or specific quality control. As you state, apparently continuous particle monitoring may be appropriate in some cases. Typically, BSC's are able to handle most situations in a research environment where small volumes predominate. A production situation may be different.
As in many cases, the original poster was not very specific in the question, e.g.,
- FDA has no validation process,
- owners do not usually validate filters,
- "HVAC filters" can encompass a wide variety of products and applications.
Like you, I noted his "bioengineer" classification and made some assumptions. Sorry for the typo.
I should add that many labs seek accreditation agencies to certify the lab capability. That usually requires periodic testing, regardless of any continuous monitoring or lack thereof.
NIST, ANSI, and ISO establish the standards and the accreditation procedures for AALA, NACLA, NVLAP, ILAC, AAALAC, FLAWG, etc. Discussion on the individual standards and accreditation agencies are way beyond the scope of this discussion, or my capability to address the possibilities of the "general" question.
