Air purifiers are appliances which remove foreign substances from an indoor air supply, allowing a clean, filtered flow of oxygen to the lungs. Air purifiers are most popular with asthmatics and allergy sufferers, but can help to maintain healthy lungs for anyone, particularly individuals who spend the majority of their waking day indoors-a population which includes the vast majority of Americans.
Air Purifier Functions
Contaminants removed by means of purifiers include such common airborne allergens such as:
- Pet dander
- Dust mite waste
- Secondhand smoke
- Toxic compounds given off by paints and cleansers
- Microscopic organisms such as bacteria and viruses.
High Efficiency Particulate Air Filter (HEPA) Purifiers
The standard and most universally acclaimed style of air purifier is the High Efficiency Particulate Air Filter, or HEPA. A HEPA purifier is little more than a microscopic sieve, allowing air to flow freely through its workings and picking out foreign objects as it finds them. These are then diverted into filters, which require regular replacement.
HEPA purifiers are extremely effective, and most are able to capture objects as small as .3 microns (about one three-millionth of a meter). They are by far the most trusted and lauded by indoor environmentalists and other authorities on air purity, who often express skepticism as to the efficiency of non-filter-based purifiers. Larger HEPA units tend to be more effective in reducing contaminants than smaller ones.
Ozone-Generating Air Purifiers
Ozone-generating purifiers work by releasing electrically charged particles into the surrounding atmosphere, which attract contaminants to them in a manner much like static cling. They then careen through the room until they affix to a surface such as a wall or a floor. Such a system is less expensive because it requires no filter replacement, but possesses three main disadvantages:
- The dirty particles emitted throughout the room can create stains where they land. In addition to being aesthetically unpleasing, this may also result in the contaminants being reintroduced into the air supply during cleaning.
- Ozone purifiers do not manipulate the surrounding air flow as HEPA filters do. Because they act on whatever air happens to pass inside of them, their range is severely limited.
- Ozone purifiers emit ozone gases, which may pose a significant health risk to certain individuals, particularly small children and the elderly.
Electrostatic Air Purifiers
Electrostatic air filters operate by a similar static cling method as ozone-generating purifiers, but tend to be somewhat cleaner; as they attract airborne substances to a metal plate rather than ejecting them back out into the environs. This plate can be repeatedly washed and reused, which makes such units a less pricy alternative to HEPA filters.
In addition, electrostatic purifiers usually do not produce ozone gases. However, like ozone purifiers, they do not create their own flow of air, leading some experts to question their overall efficiency.