Indoor Air Cleaning

Indoor air cleaning, including filtration, is one of the three commonly used methods for controlling indoor air pollution.  The other two methods are source control  (eliminating or minimizing the source of the pollution) and ventilation.  Both portable air cleaning units for room-size applications and in-duct devices/filters that are installed in the heating, ventilation, and air conditioning (HVAC) system are readily available in the marketplace.  Typically, these air cleaning units have filters that need to be replaced periodically, and it is important to note the age of filters in your system and replace as needed. For in-duct devices/filters, they could be implemented primarily for removing pollutants from outdoor air, in which they would be installed at the outdoor air intake, or for removing pollutants from recirculated indoor air.  These air cleaners use various air cleaning technologies, such as filtration, adsorption by activated carbon, photocatalytic oxidation, or a combination of them.

Air cleaning technologies are designed to remove either particulate pollutants or gaseous pollutants (i.e., VOCs). Therefore, it is important to know the target pollutants to be removed and identify the appropriate air cleaning devices. Moreover, different devices have different application requirements - for example,  a clean air delivery rate (CADR) or efficiency, replacement schedule, etc.  Below are the resources that provide more comprehensive information:

In addition, emission of harmful by-products or secondary pollutants, especially the generation of ozone, has been a concern for some indoor air cleaning technologies.  The California Air Resource Board (CARB) implements an air cleaner regulation to limit the ozone emissions from indoor air cleaning devices.  For air cleaners that intentionally produce ozone, both CARB and US EPA advise against using them.  See further information on our Ozone page.