There are many types and sizes of air cleaners on the market, ranging from relatively inexpensive table-top models to sophisticated and expensive whole-house systems. Some air cleaners are highly effective at particle removal, while others, including most table-top models, are much less so. Air cleaners are generally not designed to remove gaseous pollutants.

The effectiveness of an air cleaner depends on how well it collects pollutants from indoor air (expressed as a percentage efficiency rate) and how much air it draws through the cleaning or filtering element (expressed in cubic feet per minute). A very efficient collector with a low air-circulation rate will not be effective, nor will a cleaner with a high air-circulation rate but a less efficient collector. The long-term performance of any air cleaner depends on maintaining it according to the manufacturer's directions.

Another important factor in determining the effectiveness of an air cleaner is the strength of the pollutant source. Table-top air cleaners, in particular, may not remove satisfactory amounts of pollutants from strong nearby sources. People with a sensitivity to particular sources may find that air cleaners are helpful only in conjunction with concerted efforts to remove the source.

Over the past few years, there has been some publicity suggesting that houseplants have been shown to reduce levels of some chemicals in laboratory experiments. There is currently no evidence, however, that a reasonable number of houseplants remove significant quantities of pollutants in homes and offices. Indoor houseplants should not be over-watered because overly damp soil may promote the growth of microorganisms which can affect allergic individuals.

At present, EPA does not recommend using air cleaners to reduce levels of radon and its decay products. The effectiveness of these devices is uncertain because they only partially remove the radon decay products and do not diminish the amount of radon entering the home.

For most indoor air quality problems in the home, source control is the most effective solution. This section takes a source-by-source look at the most common indoor air pollutants, their potential health effects, and ways to reduce levels in the home. EPA has recently released, Ozone Generators That Are Sold As Air Cleaners. The purpose of this document (which is only available via this web site) is to provide accurate information regarding the use of ozone-generating devices in indoor occupied spaces. This information is based on the most credible scientific evidence currently available.

When using air cleaners, dirty air is drawn into the unit through the inlet grill. Some of the units have a washable pre-filter that traps larger airborne particles. Air then passes through the carbon filter with help reduce odors and captures larger particles. The air then passes through the HEPA filter (on some models) made of tightly woven fibers. Some units have electronic ionizers which further assist in particle removal. The fan then redistributes the filtered air throughout the room.

The basic functionalities:

• A prefilter catches the larger particles as room air is drawn in.
• In the air cleaner units having a ionizing ability, billions of microscopic particles become electrically charged as they pass through a powerful electric field and thereby get caught in the air cleaner.
• After this a carbon filter removes most common odors and fumes as the "clean air" is circulated back into the room.

This method where several techniques are used, provides you with fresh, clean air to breathe and reduces breathing problems for those with allergies and respiratory sensitivity.