Air Scrubber
A HEPA-filtered unit run inside a space to reduce airborne particulate, with its clean air returned to the same room.
The short version
- An air scrubber filters the air in a room; it does not create a pressure difference.
- The same machine becomes a negative air unit when it is ducted to exhaust outside the containment.
- A true HEPA filter captures at least 99.97 percent of particles at 0.3 microns, the hardest size to filter.
- Capacity is measured in air changes per hour, calculated from the volume of the space.
- Pre-filters must be changed on schedule, because a loaded pre-filter starves the HEPA stage and airflow collapses.
What it actually means
An air scrubber pulls room air through a series of filters, a coarse pre-filter, often a secondary filter, then a HEPA final filter, and returns the cleaned air to the same room. It is used to reduce airborne particulate during and after work that generates it: mold remediation cleaning, soot cleaning after a fire, and demolition on contaminated water losses.
The distinction from a negative air machine is entirely about where the discharge goes, not about the machine. Returned to the room, it scrubs. Ducted through a containment barrier to the outside of the work area, it removes air from the enclosure and makes it negative relative to the rest of the building. Both configurations are legitimate; only the ducted one protects the rest of the building from the work area.
HEPA is a defined performance specification rather than a marketing term. As EPA describes it, a HEPA filter can remove at least 99.97 percent of airborne particles at 0.3 microns, which is the most penetrating particle size, with larger and smaller particles trapped at even higher efficiency. Filters labelled HEPA-type or HEPA-like do not meet that specification, and on remediation work that difference is the entire point of the equipment.
What it looks like on a real job
Sizing is a calculation, not a guess: the volume of the space divided into the machine’s rated airflow gives the air changes per hour, and the number of units follows from the target. A 500 cubic feet per minute unit delivers a very high exchange rate in a small bathroom and a poor one in an open living area.
On a mold job the unit runs continuously from before the first cut until after final cleaning, and it keeps running through the period between cleaning and verification sampling. Shutting it down early lets settled particulate re-aerosolize, which is a common reason a clearance test fails.
Questions we get asked
- What is the difference between an air scrubber and a negative air machine?
- It is the same equipment used differently. Recirculating inside a room, it filters the air. Ducted out through a containment barrier, it creates negative pressure so contaminated air cannot escape the work area. Only the ducted configuration protects the rest of the building.
- Will a home air purifier do the same job?
- No. Consumer purifiers move a small fraction of the air volume, cannot be ducted through a containment barrier, and cannot establish a pressure differential. They may help with general indoor air quality; they are not remediation equipment.
- How long should it run?
- Through the work, through final cleaning, and up to verification sampling, so that particulate disturbed during cleaning is captured rather than left to settle back onto the surfaces being tested.
Official sources
Everything on this page rests on the documents below. Read them yourself, they are all free.
- EPA, What is a HEPA filter?
- EPA, Mold Remediation in Schools and Commercial Buildings (Chapter 3)
- ANSI/IICRC S520, Standard for Professional Mold Remediation
- OSHA, Mold safety and health topic page
Last reviewed against these sources on August 26, 2026. These definitions are general information about restoration work and property claims in Florida, not legal advice or a coverage opinion. Your policy language and the facts of your loss control what is owed. Swift Response Restoration Inc is a licensed restoration contractor, not an insurer, a public adjuster, or a law firm.
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Related terms
Negative Air
A HEPA-filtered air filtration device that scrubs the air inside a containment and holds it under negative pressure by exhausting outside it.
Containment
A sealed work area, usually plastic sheeting held under negative pressure, that keeps contamination and dust inside the job.
HEPA Vacuum
A vacuum with a sealed HEPA filtration path, so fine particulate is captured instead of blown back into the room through the exhaust.
Indoor Air Quality
The condition of the air inside a building, which after any loss is driven by moisture, particulate, and whatever the HVAC system is circulating.