Also commonly called air cleaners, air purifiers help remove pollutants from the air, usually in enclosed structures, such as buildings and homes. Maintaining good air quality inside is important because indoor air pollution is one of the leading five health risks related to the environment, according to the United States Environmental Protection Agency, or EPA.
Significance
Using an air purifier to clean indoor air is essential in certain situations. For example, scientific studies reveal that the air inside some buildings and residences may contain more pollution than air outdoors. Since people are indoors about 90 percent of the time, reports the EPA, they may face greater risks from indoor air pollution than outdoor air pollution. Furthermore, the individuals most likely to suffer from poor indoor air quality are also the people who must spend the most time inside, such as chronically ill, elderly and young people.
Features
Air purifiers range in size from inexpensive, small portable or tabletop varieties that clean the air in one room or one area only to large, complicated and expensive models capable of cleaning the air in an entire building or residence. The second kind may require permanent installation, such as in the ducts used for air conditioning, heating and ventilation. Larger air purifiers also tend to perform better than smaller models, although neither is usually recommended for removing all gas pollutants.
Electrostatic Precipitators
The two main types of devices used to remove pollutants from the air are mechanical air filters, which trap particles in the fibers of a filter made from various substances, and electronic air cleaners. The latter externally powered purifiers come in two varieties. Electrostatic precipitators draw air through an ionization area that charges particles electrically using high voltage. The charged particles gather on a collector, or a group of plates that have the opposite charge. For effective performance, users must clean the plates to remove the accumulated particles.
Ion Generators
Alternatively called ionizers, ion generators are the second and simplest type of electronic air purifiers. Like electrostatic precipitators, they produce charged ions that adhere to particles in the air, but the ions become charged through corona discharge or ultraviolet light. Since ionizers also do not incorporate collector plates, charged particles attach to surfaces in the vicinity instead, such as furniture and walls.
Performance
The performance of an air purifier depends on its efficiency, or ability to remove pollutants from the air, and its effectiveness, or ability to decrease the concentration of pollutants within an area. Efficiency ratings are usually a percentage, and the higher the percentage, the more efficient an air purifier is.
Effectiveness depends on efficiency, as well as the amount of air the purifier has to process and where the air goes after it leaves the purifier. Highly efficient and effective air purifiers are capable of cleaning a greater percentage of the air that passes through them, and they are able to replace a greater volume of air in an occupied space with cleaned air.
