Healthy Indoors Magazine - USA Edition

HI December 2018

Healthy Indoors Magazine

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Page 25 of 48

26 | BUILDING SCIENCE Rx — December 2018 7 Reasons Your Filter Isn't Improving Your Indoor Air Quality I ndoor 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 small- er, abbreviated PM2.5 — is worse than the bigger stuff be- cause it can penetrate deeper into the lungs and more eas- ily 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 meth- ods is to filter it out of the indoor air. In most homes, the only filtering of the air that happens is in the heating and air conditioning system. But if you think you're covered just because you have a forced air HVAC system and it has a filter, let me give you a few reasons why that filter that you so dutifully change may not be helping your IAQ. (You do change your filter, don't you?) 1. No filter 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 crawl space. Sometimes they take it out and forget to put it back in. Sometimes...well, who knows! All kinds of things happen. But not only are you not improving your indoor air quality if you don't have a filter, you're also getting your duct work, blower, air conditioner coil, furnace heat exchanger, and everything else in there dirty. 2. Filter bypass Take a look at that photo at the beginning of this article. That's some serious bypass. They put a nice, deep media filter in that's capable of filtering out a lot of nasty stuff in the air. But they installed it incorrectly so quite a bit of air going through the system was passing right by — instead of through— the filter. Bypass means you're not cleaning the air nearly as well as you should.

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