Breathe Easy

At a recent party, I joined a friend on the balcony for a break from the festivities. "It's good to get a breath of fresh air," she said. That got me thinking about air quality, not just at smoky parties but at home, too.

I live in the heart of a metropolis often shrouded in a smudge of brown. Until recently I worked in a closed-design building and felt tired all the time.

Which air was better for me to breathe-the pollution outdoors or the stale air indoors? What can we do to ensure the air in our homes is the best it can be?

The Air we Breathe

Outdoor air is contaminated by pollutants such as pollen, dust, chemicals, gases, and vehicle exhaust. Nevertheless, the US Environmental Protection Agency's Total Exposure Assessment Methodology (TEAM) studies found levels of about a dozen common organic pollutants to be two to five times higher inside homes than outside.

These pollutants are potential irritants and many are toxic if exposure is chronic. People with allergies, asthma, and multiple chemical sensitivities are the first to be affected. Cleaning the air in your home is important but no one method-or one air purifier-will do the job. You need to take a three-step holistic approach: source control, ventilation, and air purification.

Step 1-Source control

Eliminate or reduce existing emissions by cleaning or removing pollution sources in your home. Maintain oil or gas furnaces or stoves, kerosene lamps, and coal or wood fireplaces to reduce fumes. Remove pressed wood cabinetry and furniture, and cleaning products made with volatile organic compounds (VOCs). Regularly clean carpets, refrigerator drip trays, and cooling and dehumidification devices to reduce breeding grounds for viruses, fungi, and mites.

Step 2-Ventilation

Ensure your home has adequate ventilation by opening windows and doors. Use fans to reduce humidity levels while cooking and showering. Be especially sure to bring fresh outdoor air indoors when painting or sanding, or when using hobby supplies that include organic chemicals.

Step 3-Air purification

Air purifiers are a third measure to improve indoor air quality. Mechanical purifiers draw air with a fan and motor and usually come with an industrial-quality high-efficiency particulate-arresting (HEPA) filter.

Other purifiers collect pollutants electrostatically on charged plates.

To remove common allergens from the air, buy a purifier capable of collecting particulates between 0.3 and 9 microns in size (a micron is one-thousandth of a millimetre). This includes mold, bacteria, animal dander, fumes, and dust mite allergens. Ninety percent of particulates, however, are 0.3 microns or smaller. Other purifiers have filters fine enough to trap these particles and some even sterilize them with ultraviolet rays.

To clean the air of odours and gases, choose a gas filter, such as activated carbon, which acts like a sponge. Small gas molecules such as formaldehyde require a chemisorber, which converts the molecules into a harmless gas.

Mechanical filters are more efficient in cleaning the air than electrostatic filters, but they are noisier and require expensive filter replacements.

Maintenance is Key

Make sure your air filter comes with a pre-filter to trap larger particles and extend the life of finer filters. Be sure that all filters are easy to change or clean, without tools. Filter change indicator lights are another handy feature.

Once filters get clogged with pollutants, air cannot flow through as easily and efficiency drops. Although purifier manufacturers commonly claim 99.97 percent efficiency, this refers to the HEPA filter alone, not the entire unit. Ultra low penetration air (ULPA) filters are rated more efficient than HEPA filters, but their greater density restricts airflow and they end up less efficient overall.

The bottom line is to do your homework before buying an air purifier and to use it in conjunction with household pollutant source control and ventilation. Taking care with your indoor air quality will help you breathe cleaner-and easier.