By Doug Hoffman

Why can’t customers just get a better filter for indoor air quality (IAQ) problems? This is a great question because it hits right at the heart of a big misunderstanding about how filtration works.

At the National Organization of Remediators and Mold Inspectors (NORMI), our IAQ classes go into quite a bit of detail to discuss the difference between filtration and purification because they are not the same thing. Filtration typically deals with air, while purification, when done properly, also cleans the surfaces.  Filtration is a passive technology, but purification is active. Let’s talk about the difference.

If I were going to catch that pesky mouse that’s been running around in my garage, a mouse trap might function well. With a little bait on the trap, I could lure the mouse to the trap. But then two things must be true: 1) The mouse must notice that it’s there, and 2) The mouse must be large enough to avoid escaping the guillotine. Mouse traps are sitting there, ready to pounce but awaiting the mouse’s decision to go after the food. It is a passive technology.

On the other hand, if I borrowed my neighbor’s cat, Cindy, she would seek and destroy that mouse, proactively going after it.

In the IAQ world of filtration and purification technologies, all fall within one or the other of these approaches. They are either sucking the pollution to a solution or taking the solution to wherever the pollution resides. NORMI IAQ/Mold Assessors recommend implementing both technologies to achieve a more holistic and comprehensive approach to reducing indoor air quality pollutants.

Filters are good dust collectors. When contaminated air moves across the filter, contaminants are collected and can then be discarded with the filter media.  However, the trapping of those contaminants is dependent on two things: 1) They are large enough to get trapped in the filter, and 2) They can be brought to the filter. Some submicron particles are so tiny that even a powerful fan couldn’t suck them to the filter, and even if they got there, they are too small to be trapped by the filter. The best filters are rated to trap particles above .3 microns, but most of the particulate in our air is much smaller than that. Try moving those tiny particles you see in a shaft of light and they’ll simply settle right back in place. This is why a better filter alone won’t solve an indoor air quality problem.

Proactive technologies, on the other hand, “seek and destroy” contaminants where they live in the air and on surfaces. Incorporating both filtration and purification is, by far, the best way to a healthier living environment. Everyone should have a good filter but shouldn’t rely only on that solution. A multi-faceted problem, especially those including mold, requires a multi-strategic solution, and that’s what our IAQ training is all about.

For more information on NORMI and the training available, contact, call 877.251.2296, or visit

Doug Hoffman is the CEO of NORMI, the National Organization of Remediators and Mold Inspectors. He can be reached via e-mail at