High-Efficiency Air Cleaners

Filtration

• High-efficiency air cleaners that use the filtration method will likely be using a high-efficiency particulate air (HEPA) filter. According to the Environmental Protection Agency (EPA), HEPA filters have a minimum efficiency of 99.97 percent with particles as small as 0.3 microns. Air cleaners may also have a carbon-based filter working in conjunction with the HEPA filter to catch air pollutants, such as smoke. The major drawback of filtration is that it does not kill or destroy the particles that the filter catches, which allows living microbes like mold spores to recirculate in the air. They are also ineffective in eliminating large particles because these particles settle before getting circulated through the filter.

Ultraviolet Light

• Ultraviolet (UV) light air cleaners force air to run underneath a series of UV lamps. Radiation from the light kills bacteria and other living organisms. UV cleaners are usually part of a whole house system, with UV lamps located in the ductwork. The EPA recommends that UV air purification be used in conjunction with a filtration system because many types of mold and other microbes are resistant to UV radiation.

Ozone Generators

• Ozone generators pump ozone out into the air to kill microbes and eliminate odors. Although ozone generators are commonly marketed as air purifiers, the EPA warns against using them because safe levels of ozone are ineffective in eliminating particles from the air. Ozone is also a lung irritant that may aggravate existing medical conditions such as asthma.

Minimum Efficiency Reporting Value

• Air purifiers are rated according to their Minimum Efficiency Reporting Value (MERV). MERV ratings range from 1 to 20 and indicate the efficiency of a particular air purifier. The The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) requires that residential air purifiers have filters with a MERV 6 rating or higher. HEPA filters and ultra-low penetration air filters generally have MERV ratings in the 17-20 range.