Dri-Eaz DefendAir HEPA Deployment Procedure

Why this matters

The Dri-Eaz DefendAir HEPA 500 is the air scrubber that controls airborne particulate and odor in a contaminated or microbial water loss, and deploying it correctly is what makes containment actually contain. Run as a recirculating scrubber, it filters spores, dust, and odor out of the chamber air; ducted as a negative-air machine, it pulls the containment to negative pressure so contaminated air cannot escape into clean parts of the building. Set it up wrong (undersized for the volume, wrong filter stage order, exhausted into the building instead of outside, or no negative pressure where you needed it) and you either fail to clear the air or actively push contamination where it does not belong. This procedure covers air-change sizing, filter staging, recirculation versus negative-air mode, and the containment integration that the DefendAir is meant to support.

Materials and prep

Confirm the job requires air scrubbing or negative air: Category 2 or 3 water, visible microbial growth, demolition that will release particulate, or odor control. Calculate the chamber volume (length by width by height) so you can size air changes per hour against the unit's airflow rating.

Gather: the DefendAir HEPA 500 with a new pre-filter, optional carbon or second-stage filter, and a seated HEPA filter; ducting and a collar if running negative air; poly sheeting, zipper doors, and tape for containment; a manometer or differential pressure gauge to verify negative pressure; and category-appropriate PPE. Inspect the HEPA filter seating and the gasket; a HEPA stage that bypasses around a poor seal does nothing. Stage the filters in order: pre-filter first to catch large particulate and protect the HEPA, then any activated-carbon stage for odor, then the HEPA as the final stage. Never run without the pre-filter; it is what extends HEPA life.

Step-by-step

1. Build the containment. Seal the work area with poly and a zipper door, isolating it from clean spaces and the HVAC return. The DefendAir only controls the air it can reach, so a leaky containment defeats the deployment.
2. Size the air changes. Divide the chamber volume by the unit's airflow to get air changes per hour at a given speed; add units or raise speed until you meet the air-change target the job demands (higher for active demolition or microbial work). One DefendAir clears a limited volume, so large chambers need multiple units.
3. Choose the mode. For particulate and odor control inside a sealed chamber, run recirculating: the unit draws chamber air, filters it through pre, carbon, and HEPA stages, and returns clean air to the room. For negative air, duct the clean exhaust outside the containment (ideally outdoors) so the unit pulls the chamber to negative pressure and contaminated air can only flow inward through the zipper door.
4. Set negative pressure. In negative-air mode, run ducting through a sealed collar in the poly to the exterior or to a clean exhaust path. Verify the chamber is at negative pressure with a manometer; the containment poly should draw slightly inward.
5. Position the unit. Place the scrubber to set up a circular sweep of chamber air so the whole volume passes through the filters, not just a corner. Keep the intake away from the cleanest air and the exhaust away from re-entraining into the intake.
6. Run continuously. Air scrubbing and negative air run around the clock for the duration of the contaminated work; do not cycle them off between visits.

Inspection and QA

Verify negative pressure with a manometer reading and by the inward draw of the containment poly; document the differential. Confirm the air-change calculation matches the installed units and speed for the chamber volume. Check filter loading: a clogged pre-filter starves airflow and drops your air changes, so inspect and replace the pre-filter on schedule and the HEPA per its service life or pressure-drop indicator. Confirm the HEPA gasket is seated with no bypass. Document the mode (recirculation or negative air), the unit count, the air changes achieved, the negative-pressure reading, and filter-change dates. At demobilization, bag the loaded pre-filter and any contaminated media as category-appropriate waste and decontaminate the housing.

Track filter life by pressure drop, not by the calendar alone. As the pre-filter and HEPA load, static pressure across the stack rises and airflow falls, which silently erodes your air-change rate even though the unit still runs. A unit set to clear a chamber on day one may be moving far less air by day three with a clogged pre-filter, so re-verify air changes against current airflow at each visit on a dusty or demolition job. When staging multiple units in one chamber, position them so their sweeps reinforce a single circulation pattern rather than fighting each other, and keep each unit's exhaust clear of every unit's intake to avoid re-entraining filtered air back through the stack. On negative-air jobs, log the manometer reading at every visit; a pressure that has drifted toward neutral signals a containment breach or a loading-induced airflow drop that must be corrected before the work continues.

References

• ANSI/IICRC S500-2021, Standard for Professional Water Damage Restoration, Section 8 (Safety and Health) and Section 12 on containment and air quality control for contaminated water.
• ANSI/IICRC S520-2015, Standard for Professional Mold Remediation, on HEPA filtration, containment, and negative pressure for microbial work.
• EPA, Mold Remediation in Schools and Commercial Buildings (EPA 402-K-01-001), on negative pressure and HEPA air filtration.
• Dri-Eaz DefendAir HEPA 500 operating manual for airflow ratings, filter staging, and ducting setup.