HEPA Air Filter and Allergies

Allergens

• Air filters will remove contaminants that are lighter than air, including dust mites, pet dander and mold spores. HEPA filters also reduce the presence of cigarette smoke, which is an irritant for many allergy sufferers. Heavier particles, such as dirt, are better removed via a vacuum cleaner equipped with a HEPA filter.

Qualifications

• In order for a filter to be considered a true HEPA product, it must trap at least 99.97 percent of all particles in the air that are .3 microns or larger. These include chemical fumes and bacteria, in addition to dust and pollen. Some HEPA filters are highly efficient, removing the same percentage of particulates as small as .1 micron.

True HEPA

• HEPA-like filters will not work as well as true HEPA filters because the micron rating is likely to be different. Another factor that determines the effectiveness of a HEPA filter is the CFM (cubic feet per minute) rating of the air cleaner in which the filter is located. The higher the number, the more the filter will process each hour, resulting in more particulates being trapped. Powerful cleaners are usually in the range of 350 to 400 CFM.

Technology

• HEPA filtration works, in part, because of the zig-zag or accordion design of the filter, which acts as a maze of folded fibers. This structure makes it virtually impossible for undesirable or harmful agents to move through the filter as they twist and turn and sometimes collide with other particles to find a way out. Particles end up sticking to filter fibers, which have a paper-like structure on one side and are made of polymer on the other. Air must pass through the filter in order to be cleaned. Some HEPA air cleaners use a pre-filter to trap large contaminants prior to reaching the main air filter, thus extending the life of the more expensive HEPA units.

Replacement

• Because HEPA filters trap particulates and don't allow them to be reintroduced to the environment, they need to be replaced periodically for an air purifier or other appliance to remain effective in removing allergens from the air. Check manufacturers' guidelines to determine replacement frequency. The more an air cleaner is used, the more frequently a filter will need to be replaced. Most applications require new filters every three to six months.