HEPA, high-efficiency particulate air, is a filter performance grade that captures at least 99.97% of airborne particles 0.3 microns in diameter, the size that is hardest to trap, which makes it the standard for capturing mold spores during cleaning and air filtration.
What is HEPA?
The 0.3-micron specification is deliberate: that particle size is the most penetrating, so a filter that catches 99.97% of those catches a higher fraction of both larger and smaller particles (EPA, What is a HEPA filter?). Mold spores typically run from about 2 to 10 microns, well within HEPA's capture range, which is why HEPA vacuums and HEPA-filtered negative air machines are specified for mold work. A "HEPA-type" or "HEPA-style" filter that does not meet the 99.97% spec is not HEPA, a distinction worth catching on a remediation invoice.
Why it matters to a mold inspection
The remediation answer for settled spores is HEPA vacuuming and damp wiping, and the air-cleaning answer during work is HEPA filtration, so HEPA shows up in nearly every protocol. The EPA's remediation guidance specifies HEPA vacuums for cleaning and HEPA filtration on negative-air units (EPA, Mold Remediation in Schools and Commercial Buildings). A clearance inspector verifies that the equipment used actually met the HEPA standard, since a non-HEPA vacuum spreads the fine spores it fails to capture. See HEPA and PPE in mold work and containment and negative air.
MoldMind's protocol output specifies HEPA filtration and vacuuming as structured scope items, so the required filtration grade is explicit, not implied.