Why should I be concerned about indoor air quality?
Millions of people across North America suffer from respiratory conditions, bodily irritations, illness and other health problems caused or aggravated by environmental air pollution. Since your home is an enclosed environment, indoor air is on average five times more polluted than the air outside. Sources of indoor air pollution are dust , pollen, cigarette smoke, volatile organic compounds, vapours from household liquids and biological material in the air. These particles and gases can accumulate as a result of energy conservation measures (e.g., sealing cracks around doors and windows), and affect your health.

Improving your indoor air quality has significant benefits for people who experience adverse health effects caused by indoor air pollution. Headaches, chronic fatigue, itchy skin, nervous problems, nosebleeds, allergies, asthma, or other respiratory illness could be due to the quality of the air in your home (provided other causes have been ruled out by a doctor). If your home has special features such as extensive woodwork, antiques, and artwork, they all need to be protected from dirt, molds, and air that is too dry.

Do I really need to buy a piece of equipment to solve the problem? Follow these three steps before you start shopping:

1. Try to determine as accurately as possible what causes your symptoms (ask your doctor for help). For instance, it would be helpful to know that you are allergic to molds, or that solvent fumes (e.g., from paints, glues, etc.) give you headaches.
2. Once you have an idea of what the offending contaminants are, try to locate their source and eliminate them if you can. Do you have a wet crawlspace where mold is breeding? Does your spouse keep fuel oil, paints, or pesticides in the garage attached to your house?
3. If you can't eliminate the source of the trouble, seek the help of a professional HVAC contractor who has experience solving indoor air quality problems. A good contractor should recommend that you follow steps 1 and 2 before you talk about solutions to your air quality problems. If they don't, then look for someone more experienced.

What kind of air cleaning products should I consider?
Most air cleaning products fall under one of two categories:

• Air-cleaning filters trap particles. They come in a variety of types and efficiencies. Some air cleaners, such as those with HEPA filters, are 99.9% efficient. When combined with charcoal, can remove mold spores and toxic gases.
• Air purifiers use ultraviolet light to kill molds and eliminate the odours associated with some volatile organic gases (paint thinners, glues, pesticides, etc.).

Exactly which product you need depends on what you're trying to eliminate. Carefully read the manufacturers’ literature provided by your contractor on each product.

Will a ventilator help improve my indoor air?
Mechanical ventilators are extremely important for exhausting stale indoor air. The two categories of ventilators are :

• local ventilators
• whole-house ventilators

Local ventilators exhaust locally produced humid air, odours, gases, and particles. Kitchen range hoods and bathroom exhaust fans are local ventilators. If you operate a workshop inside your home or garage and you work with chemicals, you should install a local ventilator to remove harmful contaminants.

Whole-house ventilators continuously exhaust a home's entire volume of stale indoor air. They also bring in an equal volume of fresh outside air. These ventilators can help to control humidity and dilute harmful gases (off-gases from insulation and press-wood furniture, carbon monoxide and other gases from cigarette smoke, etc.). Whole-house ventilators are generally sold as heat-recovery ventilators (HRVs) or energy-recovery ventilators (ERVs). Both types recover some of the energy you've put in to the air before it is exhausted outside. For example, in the cooler months, an HRV extracts most of the heat from indoor air before sending it outside.

I know humidity is important for indoor air quality, but how do I control it? Ideally, the level of relative humidity inside your home should be between 30 and 50%. If you're not sure where the level is, you can buy a hygrometer, which measures relative humidity. If your home is either quite dry or quite humid, you can probably already feel it. Excess humidity is particularly important to control because many molds, bacteria, dust mites, and viruses love humid air.

If you have dry indoor air: You'll need to add humidity with a humidifier. Portable humidifiers from the hardware store won't humidify your whole house and they are notorious for breeding germs. Choose a power humidifier, which is an accessory that attaches to your furnace and is controlled by a humidistat. Power humidifiers are either drum or flow-through style.

Drum style humidifiers have a pan of water over which air passes. This is a standing source of water, so if it is not scrupulously cleaned every month, mold and bacteria can easily be distributed throughout the house by the furnace fan.

Flow-through humidifiers use water that circulates continuously, and is eventually drained out of the system if it does not evaporate into the air. A flow-through humidifier is the safer option for preventing germ circulation.
If you don't have a forced-air heating or cooling system, there are special whole-house humidifiers available. These supply humidified air through a single outlet duct, which equalizes the humidity throughout the home.

If you have humid indoor air: In addition to a portable dehumidifier (or perhaps a few, depending on the degree of the problem), a central air conditioning system will help control humidity when it is the biggest problem—in the summer.