Air Scrubbers


Air scrubbers are machines that collect contaminants in the indoor environment.

The S500 IICRC flood standard and S520 mold standard call them Air Filtration Devices or AFD’s.

Scrubbers (AFDs) are most often used to reduce high levels of mold and bacteria in indoor environments. The most obvious situations are flooded buildings with high mold levels and sewage backflows into buildings creating hi bacteria count.

They have “pre” filters that collect the “big stuff”, sometimes another charcoal filter for odor and a final “HEPA” filter for the really small particles. Particle size is measured in microns. The period, at the end of a sentence, printed by a printer, could be 50 to 250 microns, depending on the “spreading” of the ink. Most people can’t see smaller than 50 microns. A microscope is needed to see a single micron.

A  HEPA or High Efficiency Particulate Air filter catches particles as small as .3 microns. That’s 99.97% of whatever tries to go through it.

Some have added ultra violet lights to their units, for disinfecting.  


A new attitude has developed, recently. Some say that thousands of cubic feet of airflow per minute, even in a category 1 (relatively clean) flood could dislodge enough mold and bacteria, embedded into the cracks and crevices in the room, to make it an unhealthy situation. Some companies are installing scrubbers on every category of flood job. Many companies report a positive attitude, on this idea, from insurance companies.

An AFD has a “capture zone”. This capture zone is the area, extending out from the unit, from which particles will be pulled in. Airflow from fans can increase the ability, of the scrubber, to pull particles out of the environment by circulating “stuff” outside of the units’ capture zone.


These machines are rated by the volume they can filter - Cubic Feet per Minute or Hour. (ends up being the same) The IICRC S520 says they want the space in a level 3 mold situation (bad) filtered four times every hour. If we have 1000 cubic feet in our space and it needs to be filtered four times every hour, that’s 4,000 cubic feet per hour. It’s now as simple as dividing by the rating (cubic ft/hr) of the units available, to figure how many are needed.


These units are sometimes used to make an environment safe enough for workers to be there without having to wear personal Protection Equipment.

Containment can be another tool. This means blocking off the area, to maintain “safe” areas for workers and occupants. The area of contamination still needs filtering.


Often people, with a low tolerance for mold and pollen, will run a filter device in their homes to help lower the particles that can cause them to have allergy problems.

Sometimes, hepa filter material can be installed under an h-vac vent cover to help filter particles going through the ductwork. This is NOT a substitute for an air scrubber, in serious situations.



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              Dennis Klager
              IICRC Instructor


Copyright 2012 by Dennis Klager