What the best air purifier has

  • HEPA filtration. HEPA filtration is regarded by experts as the most effective type of filtration for removing allergens and small particles from the air. Other filters are designed to mimic this effectiveness, but few achieve the ability to remove particles down to 0.1 microns in size or smaller.
  • High maximum air-exchange rate. Maximum air-exchange rate refers to the amount of air an air cleaner is capable of passing through its system in a minute. Air purifiers with higher maximum air-exchange rates will clean the air faster than those with lower rates.
  • Filter-change alert. Many air purifiers come with a counter to let you know when it's time to change the filter. Some operate on a daily-countdown basis, while others actually base this information on the state of the filter.
  • Dust sensor or air-quality monitor. A few air purifiers have automatic sensors to detect how polluted the air is, with the ability to adjust the purifier's cleaning speed accordingly without intervention. This, of course, provides users with less precise control over energy consumption and noise levels, but it's a useful feature if you'll be using an air purifier in a non-occupied space.
  • Several fan speeds. Most air purifiers have multiple fan speeds, which adjust the speed at which the air is cycled through the unit. There's a direct correlation between higher fan speeds and more noise, however.
  • Large capacity. If you need an air purifier for a small space, more affordable options are practical. But for larger rooms, you'll need to purchase a more expensive model capable of handling more square footage.
  • Reasonable cost of ownership. Most air purifiers have long-life filters that must be replaced every three to five years. Some models have more than one filter, while others come with a permanent filter meant to be vacuumed periodically instead of replaced. The more frequently you have to replace the filter, the more it will cost you over time.

Know before you go

Do you want a whole-house or room air purifier? Experts say that a room air purifier may not be necessary for most individuals. Some owners say they've experienced significant relief from allergy symptoms with the use of a $25 furnace filter that works with an existing household appliance.

Do you have severe allergy or asthma symptoms? Owners and experts agree that for individuals suffering from severe allergy or asthma symptoms, the investment in top-of-the-line air purifiers is worth it. But if you suffer from only mild symptoms or simply want to reduce smoke or pet dander in your home, a more affordable model can do the trick.

How much space do you have? Air purifiers can be heavy and bulky, with some requiring a few feet of space on all sides. Be sure to measure your available space and allow a few feet on each side before you buy.

What room will you use an air purifier in? If you're planning to use an air purifier in your bedroom, for instance, you'll want to choose a model with an acceptable noise level that you can tolerate while sleeping. In living spaces, choose an air purifier with adjustable speed settings so you can turn it up to a higher setting when you're not in the room to be disturbed by the noise.

Value expectations: The dollars and cents of it

Air purifiers aren't cheap to own. Many cost several hundred dollars up front, and most replacement filters aren't cheap. For those suffering from severe allergies or asthma, the cost is often worth it. Others should try more affordable options, such as furnace filters, which cost significantly less and can be just as effective for most people. Some air purifiers require more frequent filter replacements, which adds to the cost over time. Owners suggest purchasing multiple filter packs online to save money. While there aren't a lot of complaints about malfunctioning air purifiers, many models offer warranties of five years for peace of mind.

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