Changing furnace filters

Do you ever wonder what household dust is actually made of? Well, I found out. A lot of it is dead skin.

When you scratch, towel off, file your nails, dress or undress, you discard bits of dead epidermis, which become household dust. So 'dusting' the furniture is really 'de-skinning'.

There are other treats mixed in with the dead skin dust, like pollen, plant and mould spores, pet dander, lint, bacteria and dust mite poop.

To make matters worse, most North Americans spend 90% of their time indoors. And with all the modern emphasis on efficiency, some homes are so airtight that airborne particles get trapped indoors and can't escape. So the air inside many homes is two to five times more polluted than outdoor air!

Your furnace filter can help. So can an expensive, stand-alone air filtration device, but today I'm talking strictly about the filter in your forced-air heating/cooling system.

If your current furnace filter is inefficient, old or dirty, the air you're breathing is probably thick with particles. A failing filter means the job of cleaning the air falls to your hardworking nose and sinuses, which is probably why our culture is facing a wave of chronic respiratory diseases, and why Canadians spend over $12 billion a year on costs linked to respiratory problems. By comparison, furnace filters are cheap.

So if you want to help your family avoid allergies, asthma, sinusitis, influenza and bronchitis, lower the particle count in your home by using better furnace filters. And change them regularly. I mean it.

The filter aisle is rife with variety. Choosing the right filter is easier than it looks, because many of them are so lame you don't want them. This is what's available:

Disposable panel filters: Low-priced and virtually useless, these babies shield the blower and coils of your furnace. They don't trap smaller airborne contaminants that mess with your health. They're made of cloth, fibreglass, open-cell foam or synthetic fibres. They're so porous you can see through them. They remove 10% or less particulate from your air, and only the really big particles. Often sold in 3-packs, which camouflages their flimsy composition.

Washable/reuseable filters: These seem like a good idea, but it's hard to get them truly clean even with the garden hose set on 'Stun'. If you're going to buy one, buy the kind that are electrostatic. And be ruthless in your cleaning procedures. Many washable filters are ineffective at capturing small particles and allergens (i.e. smoke), according to research done by the U.S. Environmental Protection Agency and the American Lung Association.

Pleated filters: This is just a flat filter with pleats to increase the surface area, so more particles are collected. However, the filter can get clogged up with particles, making it harder for air to pass through, so your fan works harder and your furnace runs longer. Therefore you must change these filters frequently to ensure proper airflow.

High Efficiency Pleated filters are made of electrostatically-charged fibres designed to attract tiny particles that other filters don't catch, including smoke. High-efficiency filters, like the Filtrete from 3M, capture up to 30 times more allergens than standard fibreglass filters. The Filtrete is the only filter endorsed by both Canadian and American Lung Associations. Since really small particles are the worst culprits, making up 99% of contaminants in indoor air, these filters are a great idea. Replace them every three months. They cost about $25; well worth it. You'll breathe better, and you won't have to dust as often.

Getting Started

Before changing your filter, turn off the power to the furnace fan.

Locate the filter. This can be straightforward or wildly irritating, depending on your furnace model and your level of alertness.

Hint: Your filter is located in the return grill, in the main return near the furnace, or inside the furnace near the blower. If you can't find the filter, blame your parents for their choices that somehow led to you living in a cold climate where you have to know stuff about furnaces. Then consult the furnace manual. If all else fails, call a heating contractor and watch them change the filter. Then, for future reference, paint huge irate arrows all over the furnace indicating the location of the filter.

Out with the Old

Grasp the edge of the filter and slide it out of its channel. If you still haven't found your filter, it may be hidden behind a door or panel that lifts or swings open. Tip: The door or panel will be indistinguishable from the rest of the ducting, and it won't open without a fight.

In with the New

Before installing, look for an arrow on the edge of your new filter. This arrow indicates the required direction of airflow. Position the filter so the arrow points toward the blower motor and related machinery. Putting the filter in backwards decreases its efficiency, so get it right.

Timing

Most households should replace filters every three months. However, if you've been doing dusty renovations, burning candles or smoking inside the house, you'll need to change your filter more often. If anyone in your family suffers from asthma, allergies or breathing problems, try changing your filter monthly to keep the indoor air as clean as possible. And run your furnace fan continuously throughout the year. The filter can only trap contaminants if the blower is running.

Bonus air quality tip:

A pair of pantyhose does not make an efficient dust filter for your dryer. The last time I bought a second-hand dryer it came with a pair of support hose tied onto the exhaust. Each leg was swollen with dryer lint. The person who sold me the dryer explained that the pantyhose acts as both lint collector and humidifier, since the moist air from the dryer fills the house after escaping the pantyhose. I said, "So that explains your persistent cough." Please ensure your dryer is properly vented. End of lecture.

More about indoor air quality:

• Ontario Lung Association's "Clean Air Now" Movement - C.A.N. DO