Air Scrubbers and Negative Pressure

Why Containment Exists

Removing mold disturbs it. Cutting drywall, pulling carpet, and scraping framing all release far more spores into the air than the undisturbed growth ever would.

Without containment, a remediation project spreads contamination through the rest of the building. This is the single most common failure in unqualified work — the mold gets removed from one room and distributed everywhere else.

What an Air Scrubber Does

An air scrubber is a blower with a filter train, typically a pre-filter, an optional carbon stage for odor, and a HEPA filter. HEPA filtration captures at least 99.97 percent of particles at 0.3 microns, which covers mold spores comfortably.

Run inside the containment, it continuously reduces airborne spore concentration during work. It is doing the most useful thing on the job site, and it should be running before demolition starts, not after.

How Negative Pressure Works

The same equipment can be ducted to exhaust outside the containment. Removing air faster than it enters makes the enclosure lower in pressure than surrounding areas, so air flows in through gaps rather than out.

That inward flow is what keeps contamination inside. Done properly, the plastic sheeting visibly pulls inward. If containment sheeting is billowing outward, the pressure relationship is backwards and the setup is actively pushing spores into the rest of the building.

What a Correct Setup Looks Like

Questions Worth Asking

Ask where the exhaust is going. Ask whether HVAC registers in the work area will be sealed. Ask when the scrubbers start relative to demolition.

These are simple questions, and a contractor who cannot answer them clearly is telling you something useful about how the job will run.