It might not be pleasant to think about, but the air we breathe is full of contaminants—dust, pollen and mold, to name just a few, as well as noxious gases, such as formaldehyde.

Surprising fact: Air is actually the number-one way that our bodies are exposed to contaminants in the home-in fact, we inhale about 35 pounds of air per day.

Unfortunately, dirty air can have significant effects on your health. For example, several studies have strongly linked air pollution to heart disease, asthma and depression.

While you can't eliminate all airborne pollutants, it's always wise to take basic steps to improve your indoor-air quality. These include frequent vacuuming and well as efforts to ventilate your home, such as opening windows and using a kitchen range hood and bathroom exhaust fans.

Air purifiers can also help. What's more, these devices can be especially beneficial for people with allergies or chemical sensitivities. What's right for you?

Choosing The Right Air Purifier

Air purifiers are available in portable devices designed for individual rooms or whole-house units that are built into your central air-conditioning or forced-air heating system. If you want air purification in your entire home, it may be cost-effective if the air ductwork is built in. However, most people get good results in the areas where they spend the most time with one or more portable units.

Important: Because there are so many options when buying a portable air purifier, it's easy to make mistakes that end up costing you money and/or prevent you from getting the pollution-fighting features you really need…

Mistake 1: Getting the wrong type of air purifier. There are two main types of air purifiers-units that remove particles (such as dust, pollen, mold and pet dander) and those that remove gases/odors (such as paint fumes and formaldehyde from glue in wood furniture). Some units remove both particles and gases/odors.

To determine which type of air purifier you need, ask yourself, What am I trying to get rid of?

Allergy and asthma sufferers often will want an air purifier that removes particles...someone who is chemically sensitive will want to eliminate gases and odors.

Air-cleaning devices designed to capture tiny particles from the air typically use high-efficiency particulate air (HEPA) technology. HEPA filters remove 99.97% of particles as small as 0.3 microns. For reference, a single hair is about 70 microns wide.

Air purifiers designed to remove gases and odors typically use activated charcoal or other material that binds to the pollutants. If you want to get rid of particles and gases, look for a purifier with both HEPA technology and a material such as activated carbon.

Important: If germs are your concern--for example, if you live with a person who is chronically ill or who has a compromised immune system-you might opt for an air purifier that uses ultraviolet (UV-C light technology. This type of air purifier is frequently used in hospitals and destroys germs such as certain types of viruses and bacteria. The "C" stands for the frequency of UV light that kills germs.

Mistake 2: Not checking a unit's efficiency and certification. A critical factor when selecting an air purifier is the device's Clean Air Delivery Rate (CADR), established by the Association of Home Appliance Manufacturers (AHAM). This numerical rating measures how quickly a portable air purifier can remove pollen, dust and tobacco smoke from a certain square-foot dimension. Specifically, it measures how much air is moving through the filter and the volume of filtered air delivered by an air purifier.

The higher the number, the better. Maximum CADR values are 450 for pollen and smoke and 400 for dust. For a list of certified air purifiers with their CADR values, visit the AHAM Web site,

Your room size helps determine the most appropriate CADR. If there's, say, a smoker in the home, the AHAM recommends looking for a unit with a "tobacco smoke CADR" of at least two-thirds of your room's area. For example, a 10-foot by 12-foot room (120 square feet) would require a CADR of at least 80.

If you're older, have a compromised immune system or are particularly sensitive to chemicals, be sure to look for a bigger filter, more powerful fan and a high CADR, and ask to see the filter itself. If it looks thin and flimsy, it probably won't clean the air very efficiently.

Two of the best: The Rabbit Air MinusA2 Ultra Quiet HEPA Air Purifier, (cost: $459.95) can be custom-designed to filter chemical gases, airborne bacteria, pet dander or tobacco smoke. The Idylis 280 for medium-to-large rooms, (cost: $249) also includes a UV-C light.

If you have allergies or asthma, you may also want to visit www.asthmaandallergyfriendly com to see whether the air purifier you're considering has been certified by the Asthma and Allergy Foundation of America (AAFA).

Mistake 3: Not placing the air purifier in the right location. It sounds obvious, but the key to achieving the cleanest air possible is to ensure that the polluted air actually passes through the filter. Many contaminants will never reach a small device that is located, for example, in the corner of your bedroom.

For the best coverage, you may wish to purchase several air purifiers depending on how big an area they can clean-or at least shut the door to the room with the single air purifier to keep out nonfiltered air.

Mistake 4: Not changing the filter often enough. Manufacturers provide a schedule of recommended times to change the filter-carefully follow these recommendations to keep your unit running in peak condition. Dirty filters lose effectiveness over time, and this could result in higher electricity costs if the air purifier has to run for longer periods of time to clean the air.

If your air is especially dirty, you might need to replace the filter every few months or more of ten)...if it's reasonably clean, once a year (or less often) may be sufficient. Many units come with filter-change sensors that alert you when they're clogged, often based on airflow reduction

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