Air Cleaners

Air Cleaning
There are three basic strategies that can be used to  reduce the amount of pollutants in indoor air. Ranked by the United States Environmental Protection Agency in order of effectiveness, they are; source control, ventilation, and air cleaning. Source control involves reducing individual pollutants at their sources. This is generally the most effective method for reducing indoor air pollutants, though not all pollution sources are identifiable or containable. The next most effective method for pollution reduction is proper ventilation. By bringing outside air indoors, whether by opening a window or turning on a mechanical ventilation system, pollutants can be effectively diluted and sent outdoors. There are some limits to the effectiveness of ventilation due to the cost of heating incoming outdoor air. Finally, the least effective method for reducing indoor air pollutants is the use of an air cleaner. Air cleaners can be classified as mechanical filters, electronic air cleaners, and ion generators. The use of air cleaners by themselves will not ensure clean air, especially if ventilation is inadequate and there are serious pollutant sources. There are no air cleaners on the market that will remove all the pollutants from indoor air.

How Effective are Air Cleaners?
How effective an air filter is depends on how efficient the device is, and how many cubic feet per minute of air the device can handle. A device may be 95% efficient at removing particles, but only capable of handling 10 cubic feet of air per minute, essentially rendering it ineffective. Effectiveness also depends upon what size of particles the cleaner can remove, how many particles the device can capture before it is "clogged", and how well air in the house is mixed with air coming out of the device.

Types of Air Cleaners
Mechanical Air Filters
- These types of filters are located in furnaces and ducts. These filters are designed to capture large particles that may damage a furnace fan.

Pleated Filters- More efficient than furnace filters; they last longer but are more expensive.

Electronic Air Cleaners- Electrically charge particles and captures them. May produce ozone, a known lung irritant.

Ion Generators- A portable unit that removes particles from the air by electrically charging them so they attach to walls, floors, etc. May also produce ozone.

Factors to Consider When Purchasing an Air Cleaner*

  • Ion generators and electronic air cleaners may produce ozone, particularly if they are not properly installed and maintained. Ozone can be a lung irritant.
  • Gases and odors from particle collected by these devices may be re-dispersed into the air.
  • The odor of tobacco smoke is largely due to gases in the smoke, rather than particles. Thus, you may smell a tobacco odor even when smoke particles have been removed.
  • Some devices scent the air to mask odors, which may lead you to believe that the odor causing pollutants have been removed.
  • Ion generators, especially those that do not contain a collector, may cause soiling of the walls and other surfaces.
  • You may be bothered by noise from portable air cleaners, even at low speeds.
  • Maintenance costs, such as costs for the replacement of filters, may be significant. You should consider these costs in addition to the initial cost of purchase. In general, the most effective units are also the most costly.
*Taken from the United States Environmental Protection Agency, Indoor Air Facts No. 7