Calculate how many air scrubbers or negative air machines you need based on room size and application. Our calculator uses IICRC S520 mold remediation standards and EPA guidelines for air changes per hour (ACH).
Enter the length, width, and ceiling height of your containment area
Select the primary use case - this determines required air changes per hour (ACH)
How severe is the contamination or dust level?
Air Scrubber Sizing Guide
Understanding ACH
Air Changes per Hour (ACH) = how many times the entire room volume is filtered each hour. Higher ACH = faster air cleaning and better containment.
Negative Pressure
For abatement work, air scrubbers create negative pressure by exhausting filtered air outside the containment, preventing contaminated air from escaping.
HEPA Filtration
True HEPA filters capture 99.97% of particles at 0.3 microns — including mold spores, asbestos fibers, and lead dust particles.
Multiple Units
For large spaces, multiple smaller units provide better air distribution than one large unit. Position units to create airflow across the entire space.
How We Calculate
CFM Required = (Room Volume × ACH) ÷ 60
Room Volume = Length × Width × Height (cubic feet)
ACH varies by application: Mold (6 ACH), Asbestos (4 ACH), Construction (8 ACH), General (3 ACH)
Need Help Sizing Your Project?
Our team has real restoration and abatement experience. Call us for personalized recommendations.
Frequently Asked Questions
How many CFM do I need for an air scrubber?
Multiply room volume (length × width × height in feet) by the required air changes per hour, then divide by 60. A 20×20 room with 8 ft ceilings at 6 ACH needs 320 CFM: 3,200 cubic feet × 6 ÷ 60. Mold remediation runs 4–6 ACH under IICRC S520; active construction dust runs 6–12.
What is the difference between an air scrubber and a negative air machine?
Same core machine — fan plus HEPA filtration. The difference is setup. An air scrubber recirculates filtered air back into the room. A negative air machine ducts its exhaust outside the containment, which lowers the pressure inside so contaminated air can't leak out. Asbestos and lead work require negative pressure; most units on this page can run either way with ducting.
How many air changes per hour for mold remediation?
IICRC S520 calls for 4–6 ACH inside containment. Light preventive work can run at 4; heavy contamination or healthcare-adjacent projects should run 8 or more. ICRA construction guidelines go up to 12 ACH for active demolition near occupied areas.
Can one air scrubber handle a whole house?
Not effectively. Air scrubbers clean the room they sit in — walls and doorways block circulation. Run one unit per containment zone or per major room. For a 2,000+ sq ft project, multiple smaller units positioned for cross-flow beat one large unit parked in a hallway.
How often do air scrubber filters need replacement?
Pre-filters: every 1–3 days on a dusty job, sometimes daily during demolition. Secondary filters: weekly to monthly. The HEPA itself lasts 6–12 months depending on loading — replace it when airflow drops noticeably or the pressure gauge says so. Running with a clogged pre-filter kills CFM and loads the expensive HEPA early. We stock replacement HEPA filters and pre-filters for Abatement and Aerospace units.
Do air scrubbers remove odors?
HEPA filters capture particles, not gases. For smoke, sewage, or chemical odors you need a unit fitted with an activated carbon filter stage — the carbon adsorbs odor molecules HEPA lets through. Several Abatement and Novatek models accept an optional carbon stage.
See the full range of HEPA air scrubbers and negative air machines — all prices listed, no quote needed. Sizing dehumidifiers for the same job? Use the dehumidifier calculator or the full water damage equipment calculator.