Indoor air quality (IAQ) researchers have established that little bitty invisible pieces of stuff that float around in the air are bad for human health. Of course, being scientists, they don’t call it little bitty invisible pieces of stuff. They call it particulate matter (PM) or particulates.
And it turns out that the really small pieces — the stuff that’s 2.5 micrometers (0.0000025 m, or 2.5 µm) or smaller, abbreviated PM2.5 — is worse than the bigger stuff because it can penetrate deeper into the lungs and more easily find its way into your blood than the bigger particulates. The chart I included in my last article shows that PM2.5 is probably the worst indoor air pollutant overall.
And how do you deal with it? One of the primary methods is to filter it out of the indoor air. In most homes, the only place where filtering of the air occurs is in the heating and air conditioning system. But if you think you’re covered just because you have a forced-air HVAC system which has a filter, let me give you a few reasons why that filter — the filter that you so dutifully change — may not be helping your IAQ. (You do change your filter, don’t you?)
It’s true. If you don’t have a filter, you’re not gonna get much filtration. And yeah, it really happens. Sometimes someone removes the filter because it’s in a difficult spot to reach, like a crawlspace. Sometimes they take it out and forget to put it back in. Sometimes… well, who knows! All kinds of things happen. But if you don’t have a filter, not only are you not improving your indoor air quality, you’re also getting your ductwork, blower, air conditioner coil, furnace heat exchanger, and everything else in there dirty.