To reduce the contaminants that lower air quality in the home, the Environmental Protection Agency first and foremost recommends minimizing or eliminating the sources of the pollution and increasing ventilation in order to replace bad air with good.
"[Air purifiers] may help control the levels of airborne particles including those associated with allergens." - United States Environment Protection Agency (August 2009)
However, there are limitations to how much of each of these you can effectively do. Some pollution sources can be easily dealt with, but others cannot. Opening windows to increase air circulation is not always a convenient option, and as the Association of Home Appliance Manufacturers points out, ventilation is relatively poor in many modern homes, as they were designed to be "energy efficient" by reducing airflow to and from the outdoors as much as possible. The EPA therefore also recommends the use of air purifiers to supplement these other avenues of cleaning indoor air.
It is important to understand and accept the limitations of air purifiers in order to comprehend their usefulness. The EPA emphasizes that air cleaners are not meant to be a substitute for the other two methods of cleaning your home's air described above. However, in conjunction with them, the EPA says that air purifiers "may help control the levels of airborne particles including those associated with allergens."
Most air cleaners are not effective at removing unwanted gases, being designed instead to target unhealthy particles floating in the air. Among these particles, the relatively larger ones are often missed by the air cleaner because gravity pulls them to the ground more quickly than smaller particles, keeping them out of the purifier's reach.
Therefore, no one should ever expect air cleaners alone to have a significant impact on indoor air quality. Nevertheless, a high-quality air cleaner can be used to improve certain aspects the air you breathe in your home, and can be an important part of your overall air-purifying strategy.
The main function of most air cleaners, therefore, is combating smaller contaminating particles. Research has shown that good air purifiers, even those of the smaller, portable variety, are up to 90% effective in reducing these smaller particles, such as those caused by cat dander and dust mites.
The EPA has certain recommendations regarding the use of portable air purifiers. In order to achieve maximum effectiveness, the portable air cleaner should be placed somewhere away from walls or other obstructions and positioned in such a way that the clean air is blown into open, occupied areas. If there is some specific source of pollution, the purifier should be placed nearby. Such purifiers work far better when all doors and windows of the room in which they are located are closed.
In conclusion, air purifiers, while not sufficient to deal with all the hazards of indoor air pollution on their own, are a useful tool which should not be overlooked by anyone interested in keeping his or her home's air as clean as possible. When the air purifier is of good quality and used effectively, it has an important role to play in the fight against the toxins and irritants that infest our inside air.