The tight seals that make your home comfortable and energy efficient also make the indoor air more polluted. The air inside your home is five to ten times dirtier than the air outside, and Americans spend 90% of their lives indoors. Quality air purifiers have never been more important for good health.
Shopping for the right air purifier can be confusing and frustrating. Some air purifiers on the market today actually pollute the air with harmful levels of ozone, a powerful lung irritant that can be especially dangerous to asthma sufferers. Learn about air purifiers and find a safe, effective unit that’s right for your needs with this air purifier buying guide.
Common Household Air Pollutants
Different air purifiers target different pollutants, so it’s important to identify the pollutants you want to eliminate from your home before you buy an air purifier.
Airborne Particles include pet allergen, dust mite allergen, pollen, plant spores, fungi, mold, and tobacco smoke, and they are the most common cause of indoor allergy and asthma attacks. A HEPA air purifier is the best method of eliminating airborne allergens.
Household Odors and Gases include cooking odors, kitty litter, tobacco smoke, various toxins, and gaseous pollutants like indoor pesticides or aerosols. Activated carbon filters are ideal for adsorbing gases and odors that are too small to be trapped by a HEPA filter. “Adsorb” is not a typo; “adsorption” occurs when materials attach through a chemical reaction.
Volatile Organic Compounds (VOCs) are found in a wide variety of common household products: paints, varnishes, cleaning supplies, disinfectants, glues and adhesives, and even new carpet and building supplies. Look for ingredients like benzene, chloride, formaldehyde, ethylene, and toluene. VOCs can cause the following symptoms: irritation of the eyes, nose, and throat, headaches, nausea, and even severe chronic health conditions such as damage to the nervous system. The presence of VOCs can also exacerbate asthma.
Microorganisms include antigens, pathogens, bacteria, and viruses. They’re the everyday germs that make us sick. Mold is also considered a microorganism.
Air Purifier Filter Types
Different air purifier filters target different types of air pollution. HEPA air purifiers are the most popular, and they’re perfect for eliminating household allergens such as dust, animal dander, and pollen, but they’re not very good at capturing ultra-fine particles like viruses or eliminating foul odors or chemical fumes.
Because different air purifier technologies have different strengths and weaknesses, many modern air purifiers combine two or more filter types in the same unit. For example, the Austin Air Super Blend Healthmate utilizes a HEPA filter along with an activated carbon filter to help eliminate odors and fumes. Let’s take a closer look at the different types of filters:
HEPA (High Efficiency Particulate Air) Filters set the standard for air purification. 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. HEPA filters allow only very small particles to pass through them. Allergens such as pollen, animal dander, mold spores, and dust get trapped in the filter. The main disadvantage of the HEPA air purifier is that you have to periodically change the filter. The main advantage: If it’s HEPA certified, then you know it works well. Not all HEPA filters are created equal. Size matters: the more square feet of HEPA filter, the more particulates it will be able to remove. The size, material, and construction of the actual filter media all play a role in the air purifier’s performance and may account for why one HEPA filter is more expensive than another.
Ion Generators and Ozone Generators create charged particles (ions) and emit them into the surrounding air. These ions combine with impurities (like dust) in the air, forcing the impurities to cling to a nearby surface. Consequently, ion generators often produce dirty spots on nearby walls and floors because they do not eliminate impurities; ion generators simply force impurities to cling to a surface (in the same way that static electricity 空氣清新機 can make a sock cling to a shirt). Ion generators are the second most popular type of air purifiers, but they both emit ozone, a powerful lung irritant that is especially dangerous for people with asthma and other chronic lung diseases, children, and the elderly.
Electrostatic Precipitators work on the same principle of electricity as ion generators and ozone generators, but electrostatic precipitators capture impurities rather than simply forcing them to cling to an external surface. Electrostatic precipitators, such as the Friedrich C90B Electrostatic Air Purifier, 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. Be aware that some electrostatic precipitators also generate ozone.
Charged Media Filters work the same way as electrostatic precipitators, but they collect particles on 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 a HEPA air purifier. These types of units can produce ozone, but the better ones on the market do not. If you are going to purchase this type of air purifier, make sure that it does not produce ozone. The best air purifier in this category is the Blueair air purifier.
Activated Carbon Filters are rarely used alone to purify the air, but they are often used in conjunction with other filters. 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 absorb and the longer it will keep on working. When it’s full, it can’t adsorb any more and has to be replaced. Impregnated carbon filters contain an additional chemical (a “chemisorbent”) to eliminate certain chemicals like VOCs.
Antibacterial and Germicidal Filters eliminate bacteria and germs. The IQAir Clean Room H13 HEPA Air Purifier, for example, utilizes a HEPA filter treated with agents to kill airborne microorganisms. Other air purifiers, like the AllerAir 4000 EXEC UV Air Purifier, use a UV lamp to kill germs. As antigens and pathogens pass over the lamp, it emits ultraviolet waves which alter their DNA, making them sterile and harmless. Air purifiers with UV filters are often used in sterile environments such as hospitals, kitchens, daycares, and labs. In residential use, they are great for controlling mold. If you are someone who gets sick often, an air purifier with a germicidal filter may be just what you need to give your immune system that extra boost.
Pre-Filters remove large particles prior to primary filtration and come with nearly all air purifiers.
Other Factors to Consider Before Buying an Air Purifier
Area Coverage – Make sure the square footage listed for the air purifier is about the same or slightly greater than the square footage of the room where you intend to use it.
Air Changes Per Hour (ACH) – This number, also known as the ACH rating, tells us how frequently the air purifier can exchange all the air in a given room. For example, if the purifier has a ACH rating of 6 for a 20′ x 20′ room, then it is capable of exchanging all of the air in that room 6 times every hour. If you have allergies or asthma, you want an ACH rating of at least 4 and preferably 6 or 8.
Clean Air Delivery Rate (CADR) – The CADR, calculated by AHAM (The Association of Home Appliance Manufacturers), tells us not only how much air is purified, but also how well it is purified. Air purifiers that have been tested by AHAM should have the AHAM Certified seal and CADR numbers for three pollutants: tobacco smoke, pollen, and dust. The higher the CADR rating, the more effective the air purifier is against that pollutant. CADR ratings are calculated impartially and recognized by the Environmental Protection Agency and American Lung Association.
Price – Air purifiers range from affordable $100 air purifiers for small spaces to fully loaded $1,000+ air purifiers for large rooms.
Filter Replacements – If you’re buying a HEPA filter, don’t forget to check and see how much replacement filters will cost. If your unit includes both a HEPA filter and a carbon filter or other combination filtration media, they will probably need to be replaced separately, and may last for different periods of time. This can be a hassle, particularly if they are difficult to access.
Noise Level – Some air purifiers, such as the Blueair units, are extremely quiet, while others can be quite loud when operating at high power. If possible, ask for a demonstration before you buy your air purifier.
Energy Usage – Like all appliances, different air purifiers use different amounts of energy for operation. Unlike most appliances, air purifiers run continuously, so you’ll 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 mechanical air filters 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).
Air Pollution – Some air purifiers pollute the air with ozone, a powerful lung irritant that is especially dangerous for asthmatics, children, and the elderly.