Air Purifier FAQ

An air purifier will improve your health. Americans spend about 90% of their lives indoors, and the Environmental Protection Agency (EPA) estimates that, on average, indoor air is two to five times more polluted than outdoor air.

Modern homes are sealed tightly for energy efficiency. Energy efficient homes are good for your electric bill, but bad for your allergies. Those tight seals trap all kinds of contaminants in your home: pollen that blows in when a door or window is opened, cat dander that hitches a ride on clothing, or chemicals and irritants released by cleaners and perfumes. Pollutants like tobacco smoke, pollen, mold, dust, and animal dander can cause asthmatic and allergic reactions, making homes unpleasant and unhealthy for allergy and asthma sufferers. Other contaminants, like chemically reactive gases and volatile organic compounds (VOCs), can cause allergic reactions and more serious health problems.

Even if your symptoms are not noticeable now, that doesn’t mean the air inside your home is clean. According to the EPA, health affects may show up only after long or repeated exposure; therefore, it’s a good idea to clean the air in your home now, especially if you have kids. Prolonged exposure to airborne allergens and pollutants can cause allergies (and more serious health problems) to develop later in life.

HEPA stands for High Efficiency Particulate Air. HEPA air purifiers were originally developed by the Atomic Energy Commission to capture radioactive dust particles. By definition, a HEPA filter removes at least 99.97% of all particles as small as 0.3 microns.

The inlet grill draws in dirty air. In most HEPA air purifiers, a washable pre-filter traps larger particles. By definition, a HEPA filter removes at least 99.97% of all particles as small as 0.3 microns. HEPA air purifiers were originally developed by the Atomic Energy Commission to capture radioactive dust particles. Allergens such as pollen, animal dander, mold spores, and dust get trapped in the filter. Many HEPA air purifiers also contain a carbon filter to capture chemicals, odors, and gases. Once the dirty air is purified, a fan sends it back into the room as clean air.

Air purifiers are designed to eliminate impurities in the air—even those impurities which are so microscopic that they are invisible to the naked eye. Microns are used to measure the size of these microscopic airborne particles. Microns are used to measure airborne particle sizes. One micron is 1/25,000 of an inch. To give you an idea of how small this is, dust mites average around 300 microns, and a grain of sand can be over 800 microns!

Activated carbon and charcoal filters excel at adsorbing odors and gases and neutralizing smoke, chemicals, and fumes. “Adsorb” is not a typo; “adsorption” occurs when materials attach through chemical attraction. Activated carbon has been treated with oxygen, opening up millions of pores in the carbon. There are so many of these tiny pores that one pound of activated carbon has a surface area of 60 to 150 acres! This huge surface area makes it ideal for adsorbing gases and odors. These chemicals and gases are too small to be trapped by a HEPA filter, but they bond to the enormous surface area in the activated carbon. The bigger the carbon filter, the more chemicals it will be able to adsorb and the longer it will keep on working. When it’s full, it can’t adsorb any more and has to be replaced.

CADR stands for Clean Air Delivery Rate, and it is a measurement developed by AHAM, the Association of Home Appliance Manufacturers. The CADR how much clean air an air purifier delivers to a room, measured in cubic feet per minute.

The EPA advises the public to “use proven methods of controlling indoor air pollution,” which include eliminating or controlling sources of pollution, increasing outdoor air ventilation, and using proven methods of air cleaning, such as HEPA air purifiers.

Electrostatic filters use an electrostatic charge to attract pollutants and trap them on collector plates. Electrostatic precipitators use electronic cells to charge particles within the purifier and immediately trap the impurities on collector plates. The main advantage with this type of air purifier is that the collector plates never have to be replaced; they can be easily washed in the dishwasher. But if the collection plates are not cleaned frequently, they quickly lose efficiency.

Charged media filters work the same way as electrostatic precipitators, but they collect particles on traditional fiber filters instead of plates. The advantage of these filters is that they are able to collect very small particles, sometimes as small as 0.1 microns, through a combination of a filter and an electrostatic charge. The disadvantage is that, like the electrostatic precipitator filters, charged media filters lose their efficiency fairly quickly, and they can require more frequent filter replacements compared to HEPA air purifiers. These types of units can emit ozone, but the better ones on the market do not. If you are planning to purchase this type of air purifier, make sure that it does not emit ozone. The best air purifier in this category is the ultra-quiet Blueair air purifier.

No, a single air purifier will not clean the air in your entire house. Even “whole house” systems will not effectively clean the air in your entire house. You should examine your home’s indoor air quality on a room-by-room basis. The bedroom is the most important room in terms of air quality, since you spend about a third of your life there. If you spend a great deal of time watching TV, you may need an air purifier for your TV room. If you don’t spend much time in certain rooms, you probably don’t need an air purifier in them, but you’ll still want to make sure your whole house is well-ventilated. It’s also a good idea to periodically open windows and let in fresh air (if you’re not allergic to pollen).

If you suffer from allergies (especially if you’re allergic to dust), then the best place for an air purifier is your bedroom. It’s essential to have clean air in your bedroom because you spend about a third of your life there. If you’re allergic to animal dander and have pets, then you may want to place an air purifier in the room where your pets spend most of their time—and keep the pets out of your bedroom! Also, you should not place an air purifier in the corner of a room; it should be at least a couple of feet away from the walls for maximum air flow.

Like all appliances, different air purifiers use different amounts of energy for operation. Unlike most appliances, air purifiers run continuously, so you may want to consider your utility bill before buying an air purifier. (If only volts and amps are listed, simply multiply the two: volts x amps = watts.) Typical HEPA air purifiers can use anywhere from 50 watts on low to 200 watts on high. For comparison sake, a typical lamp uses about 60 watts, while a typical computer uses about 365 watts. Therefore, while it’s wise to consider energy usage, most air purifiers will not create a significant difference on your electric bill.

You should make every possible effort to remove the pollutant at its source. If you think you might be allergic to mold, make sure you don’t have a mold colony growing in your basement. (If you do have mold problems, you need a dehumidifier.) If the offending irritant stems from chemicals or gases, then bringing in fresh air can result in a huge improvement. Also, some activities create high levels of pollutants—like painting, sanding, or cleaning with harsh cleaners. If possible, it’s a good idea to open up the house and ventilate as much as possible when participating in these sorts of activities.