The overall effectiveness of an air cleaner depends on its ability to trap small particles and on the amount of air drawn through it. There are no industry-wide performance standards, but the Association of Home Appliances Manufacturers (AHAM) has developed the Room Air Cleaner Certification Program. This program provides a uniform standard for portable air cleaners called the clean air delivery rate (CADR). The CADR is the amount of clean air measured in cubic feet per minute (cfm) that an air cleaner delivers to a room. AHAM publishes a list of Certified Air Cleaners that meet the standards of the Room Air Cleaners Certification Program.

Like humidifiers, air cleaners also come in styles that are part of the central ventilation system, that are room console units, and that are tabletop units. Here are the advantages and disadvantages of each style:

• Central filtration: These are air cleaners that are built into the home's central heating or air-conditioning system or a building's ventilation system. These are used when the air needs cleaning in an entire house or building. It may be difficult to add these to existing systems since a more powerful fan may be required to move sufficient air through some types of air cleaners. Another drawback is that the ventilation system must be running in order for the air to be cleaned. If you are having one of these systems installed, request one that has low-leakage, is easy to maintain, and is energy efficient. Be sure you go with a company or contractor that is very experienced in designing and installing central filtration systems.

Mechanical-electronic hybrid filters are a combination of the two filters mentioned above. For example, an "electret" filter uses an electrically charged flat or pleated fabric to attract airborne particles.

• Gas phase filters may be attached to air cleaning devices to filter specific gases, vapors, and odors since neither mechanical nor electronic filters can remove gases and odors on their own. These air cleaning units may be equipped with a chemical filter designed to removed pollutant gases from the air; activated charcoal is most widely used. Other substances used in these filters may include silica gel, activated aluminum coated with potassium permanganate (which is fairly effective in capturing formaldehyde from the air), zeolites, porous clay minerals, or molecular sieves. These filter materials may become quickly overloaded and need to be replaced often. As a result, these devices are more expensive to buy and maintain. Gaseous pollutant air cleaners are generally rated in terms of the total amount of a chemical that can be captured.

Electronic air cleaners are effective in removing airborne particles, but not gases. One major drawback to many of them is that they can produce ozone that may irritate the lungs.

• Negative ion generators: These give a charge to airborne particles so that they become attracted to and settle on walls, floors, tabletops, draperies, people, etc. Activity within a room, however, may stir up and release these settled particles back into the air. Some devices have a collector to pull the charged particles back to the unit. If a unit does not have a collector, then this kind of a unit can result in the soiling of walls and other surfaces.

There are three types of air cleaners: mechanical filters, electronic cleaners, and hybrids that are a combination of these two.

Mechanical filtration: These draw air through a flat, pleated, or high efficiency particulate air filter to trap particles.
Some of the purposes of air filters are:

• Protect the ventilation equipment from dust and dirt
• Protect furnishings and décor of the occupied space
• Reduce housekeeping and building maintenance
• Reduce furnace and heating equipment fire hazards

In the search for clean indoor air, a three-tiered system is used:

• Control the source of pollutants at their source
• Provide adequate ventilation
• Clean the air

If all sources of indoor air pollutants are controlled, then there is no need to have air cleaners; controlling the source of the pollutants is obviously the first thing you want to do. However, not all sources can be controlled. Sometimes pollutants get in no matter how hard you try to prevent them. Therefore, the last line of defense is the air cleaner. Because of that, it should always be used in addition to, not in place of, the other steps!

Source: Air Quality Sciences: IAQ resource center
Updated May 24, 2002

Introduction

Three-tiered system for cleaner indoor air

Types of air cleaners:

Mechanical filtration

Electronic air cleaners

Mechanical-electronic hybrid filters

Styles of air cleaners:

Central filtration

Console-size units

Tabletop units

"Personal" air cleaners

Effectiveness

Ozone generators

What to know if you are thinking about buying an air cleaner

Published at www.dustless.com

"One of the most highly allergenic contaminants found indoors"

One of the most highly allergenic contaminants found indoors is house dust, often heavily contaminated with the fecal pellets and skins of House Dust Mites. Estimates are that dust mites may be a factor in 50 to 80 % of asthmatics, as well as in countless cases of eczema, hay fever, and other allergic ailments. Common causes of allergy include house dust mites, cat dander, cockroach droppings and grass pollen.

Symptoms

Contact your local American Lung Association for copies of: Indoor Air Pollution Fact Sheets, Air Pollution in Your Home? and other publications on indoor air pollution.

Contact the U.S. Consumer Product Safety Commission, Washington, D.C. 20207, for copies of Humidifier Safety Alert.

To report an unsafe consumer product or product-related health problem, consumers may call the U.S. Consumer Product Safety Commission at 1-800-638-2772. A teletypewriter for the hearing impaired is available at 1-800-638-8270; the Maryland TTY number is 1-800-492-8104.

You may also contact EPA's IAQ

• Dirty air conditioners
• Dirty humidifiers and/or dehumidifiers
• Bathroom without vents or windows
• Kitchen without vents or windows
• Dirty refrigerator drip pans
• Laundry room with unvented dryer
• Unventilated attic
• Carpet on damp basement floor
• Bedding
• Closet on outside wall
• Dirty heating/air conditioning system
• Dogs or cats
• Water damage (around windows, the roof, or the basement)

Warning! Carefully read instructions for use and any cautionary labeling on cleaning products before beginning cleaning procedures.