HEPA Filtration & Air Scrubbing Flashcards

Which particle size is considered the 'most penetrating particle size' (MPPS) that HEPA filters are rated against?

Answer: 0.3 microns

0.3 microns is the MPPS because particles at this size are least affected by the filtration mechanisms of diffusion and interception, making them hardest to capture.

When establishing negative pressure containment in a multi-story building, the negative air machine exhaust hose should:

Answer: Exit through the nearest window or exterior wall penetration

Exhaust must exit to the exterior of the building through a window or wall penetration to prevent re-entrainment of mold spores into the occupied structure.

A technician notices the smoke test shows air leaking OUT of the containment barrier. This indicates:

Answer: Positive pressure exists inside the containment — a containment failure

Smoke or air escaping outward from the containment indicates positive pressure rather than negative pressure, meaning contaminated air can spread to unaffected areas.

How should a HEPA vacuum filter bag or canister be handled after mold remediation work?

Answer: Sealed inside the containment and disposed of as contaminated waste

HEPA vacuum filters and bags must be sealed while still inside the containment and disposed of as contaminated material to prevent releasing trapped spores.

The primary purpose of using a HEPA air scrubber during the demolition phase of mold remediation is to:

Answer: Capture airborne mold spores released by disturbing contaminated materials

Demolition and material removal dramatically increase airborne spore counts; the air scrubber captures these spores before they can migrate to unaffected areas.

What does a particle counter measure during post-remediation verification?

Answer: The number and size distribution of airborne particles in the air

Particle counters measure the concentration and size distribution of airborne particles but cannot distinguish mold spores from other particles without laboratory analysis.

If a negative air machine's airflow (CFM) decreases significantly during a project without changing the filter, the MOST likely cause is:

Answer: The pre-filter or HEPA filter becoming loaded with debris

As filters accumulate captured debris, airflow resistance increases and CFM output drops, reducing the machine's ability to maintain negative pressure and air changes.