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Why HEPA air purifiers are the best in fighting indoor pollutants

Air purifiers with HEPA filters can capture 99.97 percent of particles as small as 0.3 micron, which is far smaller than the diameter of a human hair.
Air purifiers with HEPA filters can capture 99.97 percent of particles as small as 0.3 micron, which is far smaller than the diameter of a human hair. (von_freiesleben)

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Those who suffer from allergies know the sometimes eye-watering effects of exposure to pollen or pet dander. But breathing certain pollutants can be more serious: Small particles of 10 microns in diameter or less, like those found in dust and smoke, can make their way deep into the lungs, aggravating them and potentially causing asthma attacks and even heart attacks in people with heart disease.

According to the Environmental Protection Agency, long-term exposure to high levels of such particles is linked to bronchitis, reduced lung function and premature death.

Add to these concerns the presence of wildfires in places such as California and the Pacific Northwest and the airborne coronavirus, and you can understand why air purifiers have surged in popularity.

A home air purifier can indeed help. Consumer Reports tests have found that the best models can effectively remove smoke particles and virus molecules. And the EPA has recommended air purifiers as an effective tool to combat viruses and smoke, noting that the airborne particles from smoke and respiratory aerosols that contain viruses are often in a similar size range, mostly between 0.1 and 1 micron. Air purifiers with high-efficiency particulate air (HEPA) filters are able to trap particles of this size range effectively.

Here are tips on selecting a model for your home.

Choose the right filter type

The best air purifiers have mechanical ­filtration systems. These use an internal fan to draw ­particle-rich air into the machine, forcing it through the complex net of ­fibers in a pleated fi­lter.

The most effective among these have HEPA filters. The HEPA ­ones have a fine mesh filter that can capture 99.97 percent of particles as small as 0.3 micron, and some particles smaller than that.

You may also see models that use other air purifying technologies, including electrostatic precipitators, ultraviolet germicidal irradiation and photocatalytic oxidation. The models with these technologies that CR’s experts have tested have shown them to be less effective.

Consider your space

It can get expensive to out­fit every room with its own air purifier, so your best bet is to choose one or two models for the areas where you spend the most time, like your bedroom, living room or home office. Then match the model to your room’s size. To do this, check for the air purifi­er’s clean air delivery rate (CADR) number.

The CADR number reflects, in cubic feet per minute or per hour, the volume of clean air that an air purifier produces at its highest speed setting. According to the Association of Home Appliance Manufacturers, a general rule of thumb is to select an air purifier with a CADR number that is at least two-thirds of your room’s area. So for a room that’s 10x12 feet, with an area of 120 square feet, you’d want an air purifier with a CADR of at least 80.

Some models have labels with three different CADR numbers, one for dust, one for tobacco smoke and one for pollen. When choosing a model to buy, focus on the CADR number for the pollutant you’re most concerned about.

Factor in future costs

Air purifiers can range in price from about $40 to more than $1,000, and Consumer Reports has identified some strong performers that cost less than $300. But keep in mind that most air purifiers have a removable fi­lter that you’ll need to replace every three to six months — at a cost of about $40 to $200 per year.

And because these appliances are designed to run 24/7, you’ll want to factor in energy costs. Look for puri­fiers with an Energy Star rating, which indicates that they use up to 40 percent less energy than regular models.

 Copyright 2021, Consumer Reports Inc.

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