Have your heating system checked and tuned up every year, and get your chimney inspected regularly.

Consumer Reports suggests placing one near your bedrooms and another in high-occupancy areas like the TV room. Caution: Avoid placing detectors to close to your heating unit, your water heater or a window, or you won't get an accurate reading.

These devices, which capture particles on charged plates or grids, are also known as ionizers or electrostatic precipitators. They are far less efficient than a true HEPA filter, even when the collection plates are clean. As happens with electrostatic filters, their efficiency will drop off precipitously as the collection plates get dirty, and homeowner cleaning and maintenance becomes an issue.

Several safety measures protect service technicians and homeowners from eye or skin UV exposure, including a lamp shutoff switch, and a sight glass for safe and easy lamp inspection. A protective cover with a safety interlock switch immediately deactivates the lamp before the service technician or homeowner can access or service the unit.

The "links" page of this Web site will take you to a number of helpful and informative sites with extensive information about allergies, asthma and IAQ.

Indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home. High temperature and humidity levels can also increase concentrations of some pollutants.

Pollutant Sources
There are many sources of indoor air pollution in any home. These include combustion sources such as oil, gas, kerosene, coal, wood, and tobacco products; building materials and furnishings as diverse as deteriorated, asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products; products for household cleaning and maintenance, personal care, or hobbies; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides, and outdoor air pollution.

The relative importance of any single source depends on how much of a given pollutant it emits and how hazardous those emissions are. In some cases, factors such as how old the source is and whether it is properly maintained are significant. For example, an improperly adjusted gas stove can emit significantly more carbon monoxide than one that is properly adjusted.

Some sources, such as building materials, furnishings, and household products like air fresheners, release pollutants more or less continuously. Other sources, related to activities carried out in the home, release pollutants intermittently. These include smoking, the use of unvented or malfunctioning stoves, furnaces, or space heaters, the use of solvents in cleaning and hobby activities, the use of paint strippers in redecorating activities, and the use of cleaning products and pesticides in housekeeping. High pollutant concentrations can remain in the air for long periods after some of these activities.

Amount of Ventilation
If too little outdoor air enters a home, pollutants can accumulate to levels that can pose health and comfort problems. Unless they are built with special mechanical means of ventilation, homes that are designed and constructed to minimize the amount of outdoor air that can "leak" into and out of the home may have higher pollutant levels than other homes. However, because some weather conditions can drastically reduce the amount of outdoor air that enters a home, pollutants can build up even in homes that are normally considered "leaky."