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 manual 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.
  • No or very low ozone. Experts say that ozone is effective in neutralizing odors and chemical gases. They also say that this is a classic case where the cure is worse than the disease as high-levels of ozone can be toxic. If you opt for an electronic air purifier, chose a design that emits low or, better still, no ozone. Skip ozone generators sold as air cleaners altogether.

Know before you go

Do you want a whole-house or room air purifier? Experts say that a room air purifier might 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 unit.

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 clearance on all sides. Be sure to measure your available space and allow for all space considerations 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 a 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. Also, keep in mind that if you can hunt down and eliminate sources of allergens and odors, you might be able to do without an air purifier altogether.

Elsewhere in this report:

Best Reviewed Air Purifiers: These are the best air purifiers as identified in reviews. We discuss top performers overall as well as budget choices for allergy sufferers and for small spaces.

Air Purifiers and Ozone: Some air purifiers emit large amounts of ozone to neutralize odors and chemicals in the air. They work, but don't buy one anyway. Here's why.

Cheap Air Purifiers: These air cleaners won't do much to remove odors, but the best are every bit as effective against allergens and other particle pollution as the very best -- and priciest -- models.

Best Small Air Purifiers: If you just need an air purifier for a small bedroom or similar space, these low cost models are surprisingly effective.

Furnace Filters and UV Air Purifiers: Looking for an alternative to a room-sized air cleaner? Here's one thing to try, one thing to avoid, and a few hints that might help make for easier breathing no matter what you opt for.

Our Sources: These are the expert and user reviews we consulted to find the top air purifiers in all prices and capacities. They are ranked in the order of their helpfulness and expertise.

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