Theoretically, air filters can remove 99.97% or more of airborne particles with a size of 0.3 microns, including dust, pollen, mold and bacteria. According to the Environmental Protection Agency (EPA), particles that are larger or smaller than that size are trapped with even greater efficiency. Two studies by Brauner et al. and Allen et al.
have shown that air filters reduced indoor concentrations of fine particles by a significant amount. Filtration was associated with a 9.4% increase (95% confidence interval, 0.9-18%) in the reactive hyperemia index and a 32.6% (4.4-60.9%) decrease in C-reactive protein. Activated carbon is the main ingredient of an activated carbon filter. This type of filter can absorb smoky odors and volatile organic chemicals (VOCs) that are hazardous to breathe. The quality of the carbon filter will determine its effectiveness in trapping smoke, VOC and odors.
For best overall results, select an air purifier that uses an active carbon filter in combination with other filters, such as a HEPA filter. An air purifier can only remove allergens while they are floating in the air. Larger and heavier allergens, such as mites, mold and pollen, settle on the ground so quickly that the air purifier cannot capture them all in time. Studies are not conclusive on the ability of air purifiers to cope with gases. CADR reflects, in cubic feet per minute, the volume of clean air produced by an air cleaner at its highest speed setting. For example, a purifier with a CADR of 250 for dust particles reduces the levels of dust particles to the same concentration that would be achieved by adding 250 cubic feet of clean air every minute.
The higher the CADR, the faster and more efficient the air purifier will be. Room air purifiers with HEPA filters often achieve the highest CADR. In our tests, a CADR greater than 240 receives an Excellent rating; 240 to 180, Very Good; 179 to 120, Good; 119 to 60, Regular; and anything less than 60 gets a Bad rating. Air purifiers are effective at reducing particulate matter in the air. Some types can generate health benefits for people with allergies, asthma and other conditions. HEPA filters are the ones that support them the most and can filter out extremely small particles. How long an air purifier lasts will depend on the particular make, model and level of air pollutants.
If routine allergies or asthma symptoms negatively affect your life, evidence that a HEPA filter improves respiratory health may encourage you to look for an air purifier. While this improves air quality, these particles remain and can recirculate in the air the next time you sweep, sit on the couch, lean on a wall, or walk on the floor. According to the EPA, a portable air purifier is one of the most effective ways to improve indoor air quality in an individual room or area. New data also reveal a stronger link between indoor and outdoor air pollution exposure and cardiovascular diseases, such as stroke and ischemic heart disease, as well as between air pollution and cancer. Air purifiers can neutralize some of the threat posed by air pollution and indoor activities. However, they cannot remove larger allergens, dust mites and pet hair that settle on furniture and carpets unless they are altered and redistributed. The following publications provide information on portable air purifiers and HVAC and furnace filters that are commonly used in homes. To make it easier, many air purifiers have indicator lights to indicate it's time to replace the filter. Some filters are reusable and washable but require meticulous maintenance so you won't normally find them in the most effective air purifiers.
However, ionic air purifiers can have negative health consequences that negate their value as an air purifier. As for the coronavirus, air purifiers with HEPA filters are able to capture the droplets in which the virus travels (when people cough, talk or breathe). Because the health benefits of using air purifiers vary from person to person and depend on the types of pollutants in your home, it's ultimately up to you whether an air purifier is worth paying for and running. This can lead to dangerous indoor air quality, and Consumer Reports does not recommend this type of air purifiers.