Working, playing, eating, and sleeping -- most of us spend about 90% of our time indoors. Since healthy lungs thrive on unpolluted air, keeping the air clean in your home and workplace is essential for good health. This is especially important for people with allergies or a lung disease such as asthma, bronchitis, or emphysema.

Indoor air pollution can cause dizziness, nausea, allergic reactions, and eye, skin, and respiratory tract irritation. If you have some of these symptoms, note whether they disappear when you are away from your home or office, or improve when you increase indoor ventilation. If so, your symptoms may be triggered by something inside your home or office.

Indoor Pollutants: Eliminate, Then Ventilate

The most effective way to control most indoor air pollutants is to eliminate the source. Improving ventilation by bringing cleaner outdoor air inside can also be beneficial. If these two methods are not successful in reducing pollutants, consider the use of an air cleaner.

Air cleaners are devices designed to remove substances from the air in rooms or buildings. Air cleaners can be very effective in removing pollutants that are present as particles in the air. (The particles must be suspended in the air -- not settled on floors, walls or furnishings -- in order to be removed.) Air cleaners have little effect on removing gases and odors.

Listed here are a variety of sources that may be polluting your home or office and suggestions on how to control them.

Secondhand smoke, the smoke you inhale from someone else's cigarette, pipe, or cigar, contains significant amounts of carbon monoxide, formaldehyde, and thousands of other gases and particles, some of which can cause cancer.
Control: Eliminate smoking. If this is not possible, increase ventilation and consider using an air cleaner. Secondhand smoke has a high concentration of particles which can be captured by some air cleaners. However, it is almost impossible to remove all the toxic gases produced by secondhand smoke.

Pet dander is a potent allergen for some people.
Control: Do not keep pets indoors. If you do keep a pet, bathe it weekly and keep it out of bedrooms. Animal dander tends to settle on surfaces where air cleaners cannot trap it.

Mold, mildew, and bacteria originating form improperly cleaned air conditioners, humidifiers, dehumidifiers, or house plants can cause allergic reactions and/or infections.
Control: Clean air conditioners, humidifiers, and dehumidifiers frequently. Use distilled water in humidifiers. Make sure that bathrooms and kitchen are well-ventilated to minimize mold growth. Spores from mold, fungi, and plants can be trapped by an air cleaner. However, these spores tend to settle on floors, furniture, and other surfaces rather than remaining suspended where they can be collected by an air cleaner.

Formaldehyde gas is released by many household products and tobacco smoke. It can cause headaches, dizziness, rashes, nausea, fatigue, and irritation of the eyes and upper respiratory tract. It can also trigger asthma attacks. Sources of formaldehyde gas include particleboard and plywood, some adhesives, carpet, upholstery and drapery fabric.
Control: If possible, remove the sources. If removal is not feasible, increase ventilation and consider covering the source with a coating. Special chemically-absorbing air filters can remove formaldehyde from the air. However, there is not sufficient information available at this time to evaluate the overall effectiveness of these air filtering units. Formaldehyde will become less of a problem in the future as the formaldehyde content of the products is controlled.

Combustion appliances (furnaces, heaters, and stoves fueled by natural gas or propane) can produce harmful amounts of nitrogen dioxide and/or carbon monoxide if not properly installed and vented. Nitrogen dioxide is a gas that can contribute to eye and respiratory tract irritation and lower your resistance to infection. Carbon monoxide is a gas that interferes with the distribution of oxygen to the body and can cause fatigue, headaches, nausea and dizziness. It can also exacerbate cardiovascular disease. Very high levels can cause death.
Control: Have combustion appliances professionally inspected annually for potential nitrogen dioxide and carbon monoxide production. Make sure that all appliances that burn fuel are vented to the outside. An air cleaner is not an effective control.

Dust mites in ordinary household dust can cause allergic reactions.
Control: Wash bedding frequently (every 2 to 7 days depending on the severity of the problem) in hot water at least 130 degrees. Air cleaners can lower the concentration of dust in the air, but have little effect on dust mites themselves.

Toxic chemicals in household products such as cleaning agents, pesticides, personal care products, paints, hobby materials and solvents can affect your health. Symptoms may include dizziness, nausea, allergic reaction, and eye, skin, and respiratory tract irritation.
Control: Follow directions for use of these products carefully. Work in a well-ventilated area. Avoid aerosols and use non-toxic products when possible. Air cleaners have very limited effectiveness in controlling most of these chemicals.

Radon gas is released by soil or rock which contains small amounts of uranium or radium. Exposure to radon has been linked to increased risk of lung cancer. Radon gas enters the home through cracks, drains, sumps, or other openings in the basement or foundation. In Washington, the soil and rock with the highest radon potential are located in the northeastern corner of the state, but no area of the state is completely free of radon risk.
Control: Test your home for radon. Inexpensive monitors are available. If levels exceed 4 picocuries, consult an expert. You may need to hire a professional to reduce the radon levels in your home. An air cleaner will not be effective.

Asbestos contained in roofing, flooring, insulation, cement or other household building materials can be released into the air if the material is abraded or if it disintegrates. When that happens, asbestos can cause disease, such as lung cancer or asbestosis. Consult an expert if you have questions about asbestos in your home.
Control: If an expert determines that asbestos fibers are being released into the air in your home or office, it may be necessary to hire a professional to remove the material. If an asbestos-containing material remains intact, however, leave it alone. The use of asbestos is being phased out. An air cleaner is not an effective control.

Should You Consider Using an Air Cleaner?

The use of air cleaning devices alone cannot assure good air quality. However, if removing the pollution source or increasing ventilation are not options or are not effective in improving your indoor air quality, an air cleaner may help. There are three types of air cleaners:

Mechanical filters draw air through a flat or pleated surface to trap particles.

Electronic air cleaners draw particles across an electrostatic precipitator to give them an electrical charge. Particles are then trapped on oppositely-charged metal plates.

Ion generators emit electrically-charged particles (ions) into room air. These ions then attract pollutant particles until they become too heavy to remain airborne. These combined particles then settle on walls, floors, or other surfaces.

Mechanical and electronic air cleaners are available either as portable units (for room use) or installations for central heating/air conditioning systems (for whole-house or building use). Ion generators come in portable units only.

Some air cleaners include, in addition to the filter or electrostatic precipitator, a carbon absorbent designed to remove some gases from the air. Over time, the absorbent will become saturated and need to be replaced. The effectiveness of these devices has not been thoroughly evaluated.

Some air cleaners use an electrical charge to generate ozone. At high concentrations, ozone destroys gas molecules and microorganisms. It has no effect on particles. Ozone itself is a pollutant with damaging health effects. It causes lung irritation and lowers resistance to lung infections. The American Lung Association® of Washington does not recommend ozone generators.

Nine Factors To Consider When Choosing an Air Cleaner

1) Efficiency
The efficiency of an air cleaner is measured in terms of the particle size that the cleaner can capture. Different air pollutants come in different sizes. In most cases, it is the very small, respirable size particles that can penetrate deep into the respiratory tract and lungs that you want to remove from the air. Biological pollutants such as mold spores and animal dander are relatively large particles (10 - 100 microns in diameter), while tobacco smoke particles are very small (less than one micron in diameter). (A micron is twenty five thousandths of an inch.) Therefore, the efficiency of an air cleaner is a significant factor.

Efficiency is expressed as the percent removal of particles of a particular pollutant or mixture of pollutants. Both mechanical filters and electronic air cleaners are available which can effectively trap both large and small particles.

HEPA (High Efficiency Particle Arresting) filters are the most efficient mechanical filtration cleaners for removing small particles. HEPA filters remove up to 99.97 percent of particles as small as 0.3 microns.

Electrostatic precipitators can also be very effective in removing small and larger particles. Current data indicates that ion generators are not effective in removing small particles from the air.

2) Clean Air Delivery Rate
The overall effectiveness of the air cleaner depends on the efficiency of the unit and on the amount of air drawn through it. Although there is no universally accepted performance standard for rating air cleaners, there is a standard for portable air cleaners called the CADR (Clean Air Delivery Rate) that you can use to compare various units. THE CADR expresses the number of cubic feet of clean air a unit delivers each minute. The more effective units have a CADR over 200.

3) Installation
Installation of air cleaners can be permanent (installed in central heating and cooling systems) or portable (units can rest on desk or table tops).

4) Location
Location of the unit in relation to the source of pollution also affects the unit's overall effectiveness. In the case of portable air cleaners, the unit should be placed so that the intake is near any identifiable source of pollutants. Make sure that the inlet and outlet are not blocked by walls or other obstructions. Cleaned air should be directed toward inhabited areas.

5) Noise
Noise generated by an air cleaner can be a concern. Check the unit at all fan speeds to evaluate noise levels.

6) Energy Consumption
Energy consumption will be increased by operating an air cleaner. Check the electricity consumption rating of the unit to compare needs and anticipate additional costs. A heat pump can help offset this increase.

7) Price
Price includes both the initial purchase price and the charge for replacement filters and other maintenance costs.

8) Maintenance
Maintenance schedules vary by type of cleaner. Most filters need to be cleaned or replaced regularly. Filters should be accessible and easily removable so they can be maintained with minimum effort. HEPA filters become more efficient with use, but they will eventually become clogged and need to be replaced. Electrostatic precipitator cells need to be washed every few months. Be sure to follow the manufacturer's cleaning and maintenance directions. Ask for information on the cost of replacement filters.

9) Ozone production and other pollutants
Possible production or redispersal of pollutants such as ozone gas, or gaseous pollutants trapped by an absorbent can be a problem. Both electrostatic precipitators and ion generators can produce small amounts of ozone. Ask whether the unit has been tested for ozone production. The FDA recommends a limit of 0.05 ppm (parts per million) of ozone in indoor air.

A Note On Air Conditioners:
An air conditioner can be a helpful allergen or particle control measure if you have allergies to, or a lung condition made worse by, outdoor dusts, mold and pollens. During warmer weather, air conditioning can be used to reduce pollen, dust, and mold spores indoors by recirculating air. Only about 10% of the air passing through an operating air conditioner is drawn from outside. The remaining 90% is indoor air. Air conditioners can also decrease the number of house dust mites and mold spores by reducing the humidity. However, be sure to routinely drain and clean air conditioner drip pans or they can become a source of mold and bacterial growth.

If your home has central air conditioning, use medium or high efficiency filters in the system to filter the outside air. It may also be possible to replace the filter in window- or wall-mounted units with a medium or high efficiency filter. Contact an air conditioning contractor to find out. If air conditioning is in use -- especially if you have installed a medium or high efficiency filter -- adding a portable air cleaner for the control of molds, pollens, or house dust mites may be unnecessary.