Do Air Purifiers Really Work?

Medical experts warn that not even the very best air purifier can make any health claims, and the EPA bluntly advises that air cleaners be only part of an air treatment plan that includes controlling the source of pollutants and improving ventilation. Still, reviewers generally agree that high-performing air purifiers are worth the investment. Many consumers with allergies, respiratory problems, sensitivity to odors, and pets report an air purifier offers welcome relief in the form of improved comfort and health.

Pricey vs. Cheap Air Purifiers

The market for air purifiers is growing, with new brands and technologies emerging at a steady clip. High-end names such as IQAir, Blueair, Austin, and Alen sit well outside the budget zone with air cleaners that often start at $500 or so. In general, pricey air purifiers do a better job scrubbing the air and pushing it back out, run more quietly and efficiently, and feature more advanced filter systems than cheaper models. Some hit medical-grade air-quality standards. They often boast conveniences such as remote and smart controls and come with longer warranties.

Still, the inexpensive air purifiers highlighted on our list can hold their own. Bearing the labels of trusted household appliance brands such as Whirlpool and Hamilton Beach, along with specialty brands like Holmes, Winix, and GermGuardian, they may be short on bells and whistles, but they win endorsements from users and experts for effective and reliable performance at a value price.

Air Purifier Types

The first step in choosing an air purifier is to identify the air quality issue(s) you want to address, such as dust, pollen, chemical vapors, and so on. Some cheap air purifiers focus more on particulates than on odors or gases, and vice versa. The Environmental Protection Agency dedicates an entire section of its website to the topic of indoor air quality and the performance characteristics of different types of air cleaners.

Models that clean the air with a physical filter are the most common and arguably the most effective, especially when outfitted with a high efficiency particulate air filter. In this setup, air is pulled in by a fan and passes through a filter that traps airborne irritants. The cleaned air is circulated back into the room. HEPA filters come in several grades, or classifications, with a “true” HEPA filter capable of trapping 99.97 percent of airborne particles — think dust, pollen, mold spores, pet dander — as small as 0.3 microns (the average human hair is 50 microns across).

Several of our top picks boast a true HEPA filter, and anyone who suffers from severe allergies or asthma should opt for an air cleaner with the highest-grade HEPA filter. Others on our list use “HEPA-grade” filters that capture 99 percent of invisible airborne particles. Reviewers hold that some of these models are absolutely viable choices for mild or seasonal allergies.

The best air purifiers rely on multi-level filtration. Typically this involves a pre-filter that traps larger particles, like pet hair and dander, and an activated carbon filter that helps absorb odors, smoke, and volatile organic compounds emitted by draperies, carpeting, upholstery, household cleaning agents, paints, varnishes, waxes, and certain building materials, among other substances. In some models, the pre-filter and carbon filter form one unit; in others they are separate.

The number of times air flows through the filter each hour is referred to as “air changes per hour, or ACH. Many experts recommend a minimum of four, although this specification is not often reported by the manufacturer.

UV Air Purifiers

Some models, including several of our picks, also incorporate an ultraviolet light (UV-C) that’s meant to destroy bacterial microorganisms as the final level of filtration. Experts note, however, that the amount of time required to do the deed is longer than the amount of time the particles are exposed to the light, thus minimizing the technology’s effectiveness. Reviewers who keep an air purifier in their bedrooms often gripe that the light on some of these models is too bright for nighttime use. It can be switched on or off at the user’s discretion.

Ozone Air Purifiers

The most controversial air purifiers intentionally convert air molecules into ozone to tackle odors. The EPA warns that ozone can damage the lungs and, at the very least, exacerbate respiratory problems. Consequently, many experts recommend against ozone-generating air purifiers.

Ionic Air Purifiers

Ionic air purifiers also produce small amounts of ozone, but supposedly at levels that do not exceed current safety standards. Instead of using a filter, ionic air purifiers catch contaminants on electrically charged plates/blades or cells. They send out negatively charged ions that attach to airborne particulates, which are then pulled down out of the air and lured back to a positively charged collector plate. Reports dating back to at least 2003 have questioned the efficacy of air ionizers. And yet, these types of purifiers remain popular with some consumers, at least in part because they have no fan, so they’re nearly silent. But the absence of a fan also means the machine catches only contaminants that happen to drift within close range. Experts note that often the particles on the charged plates can loosen and be recirculated, and some wind up settling on other surfaces.

Our inclination is to avoid models outfitted with ionic technology unless they include other means of removing airborne irritants and offer the option of shutting it off. Several of our picks include an ionizer as an optional step in the air cleaning process.

The Winix line of air cleaners uses a proprietary PlasmaWave as the final stage in the filtering process. This technology emits both positively and negatively charged ions to combine with water vapors in the air to create oxidizers that neutralize germs, odors, vapors, and gases without emitting any ozone. Also, the charge on these plasma ions is weaker, so they dissipate more quickly, leaving less potentially harmful particles floating about in the air. The PlasmaWave function can be turned on or off.

Large vs. Small Room Air Purifiers

The next step in choosing an air cleaner is determining where you will place it, as the room’s square footage affects both size and price. Small-room models intended for less than 200 square feet are always cheaper than large-room air purifiers meant for 350 square feet and up, regardless of features or performance. But a model that’s too small for the space won’t filter and recirculate the air into the room often enough. Many rooms straddle the line between small and large, so err on the large side when deciding on the best model for your space.