Healthy Home Tips: Mistakes Parents Make Trying to Clean Indoor Air

If you have a child with allergies or asthma, you probably work hard to keep your home and the air inside your home as clean as possible. But there are some things you might do or buy that can actually introduce rather than solve indoor air quality (IAQ) problems.

Let’s start with a hot-air heating and/or central air conditioning system – often a source of many allergens and irritants in a home.

1. Electronic filters are efficient in theory but lose their filtering capacity quite quickly as they get dusty. Since people rarely clean such filters frequently enough (monthly), these expensive filters (often costing upwards to $1,000 each) end up being pretty next to useless – kind of like using gold jewelry as a paperweight.

2. Washable electrostatic filters are also expensive ($100 or more) and also are rarely cleaned often enough or thoroughly enough, so in my opinion these filters are a waste of money.

3. A turbulent flow precipitator consists of several media filters stacked in a holder. Air passes over rather than through the filters. Supposedly, multiple passes of air over the pleats cause the air to rotate, and dust to deposit on the filter surfaces. In reality, despite being passed over the filters a number of times, many airborne particles get past the filter array and still enter the mechanical system, where in the presence of moisture, they can become nutrients for mold growth.

4. Ultra-violet (UV) lights are either supposed to disinfect the air or keep the system free of microbial growth (yeast, mold, bacteria). Germicidal UV has been used successfully for decades to disinfect air, but the homeowner versions do little to disinfect the air stream and cannot sufficiently clean interior surfaces in an already soiled air conveyance system. (A pivotal Canadian study concluded that UV irradiation would improve the health of millions of allergy sufferers. The study’s methodology, however, was flawed and thus the conclusion invalid.)

The best way to keep a hot air and/or central air conditioning system clean is to have the best filtration possible: a disposable pleated media filter with a MERV rating of at least 8 (MERV stands for minimum efficiency reporting value). Families with allergies or asthma should use a MERV 11 filter, like the Aprilaire, though the duct system will have to be altered to accommodate the deeper filter. Whether rated MERV 8 or MERV 11, the filter should be in an airtight filter holder, to prevent air from by-passing the filter and entering the system unfiltered; a one-inch media filter should be changed at least twice a year, depending on the manufacturer’s recommendations. (A one-inch media filter with a MERV-8 rating must be changed more often than a two-, four- or five-inch MERV-8 filter, because the static pressure builds up faster in a thinner filter, reducing the airflow.)

What else do people acquire in an effort to keep the air in their homes clean?

1. Air-to-air heat exchangers, also called energy recovery ventilation (ERV) or heat recovery ventilation (HRV), are devices that exhaust stale house air and introduce fresh outdoor air into the building. There are a few problems with these units, however. First, most lack a pre-filter to prevent the buildup of outdoor pollen, mold, plant materials, and insects inside the unit. Second, the built-in filtration within the unit itself is usually inadequate, so dust builds up on the heat exchanger. Whether in winter or summer, hotter air meets colder air within the heat exchanger, and condensation may occur. In fact, many such units that I’ve seen lack any accommodations for drainage, even when the exhausted air comes from bathrooms or the kitchen – adding even more moisture to the device. The presence of dust and moisture lead to mold growth, so it’s no surprise that almost every single HRV I’ve opened was full of mold growth. Then spores or other mold allergens are circulated in the air stream. If you have an air-to-air heat exchanger in your home, make sure you clean the interior (including the “core”) on a regular basis, and replace or clean the filter at least four times a year. If possible, eliminate the two internal filters and use in-line, external media filters at least two inches deep with at least a MERV 8 rating. If you are only thinking about installing an air-to-air heat exchanger and aren’t the type of person to take care of regular maintenance tasks, please think again and open a window now and then instead.

2. To finish off my rant, I have to complain about ionizing air purifiers. People like them because they make the air smell “clean” – like outdoor air. That fresh outdoor smell is caused by ozone – an irritating gas that is one of the major components in smog. If you want to use an air purifier, use one with a pleated media filter or a HEPA filter, and be sure it doesn’t have the air discharge at the base, which can disturb and make airborne more irritants and allergens than the machine can remove. But remember that IAQ problems aren’t born in the air itself. Air, like water, is a fluid, and like water, it carries gases and particles in its flows. So if you think that the air in your home is causing you or someone you love to cough, sneeze or wheeze, find and eradicate the sources of the airborne irritants and allergens, rather than try to “clean” the air. No air purifier can ever cleanse the air sufficiently, as long as sources of IAQ problems remain in a space.