Air purifiers: how do they work and who is one suitable for?

For several decades, air quality in the US has been improving in many areas. Facts indicated that fine, respirable particulate matter, better known as PM2.5, decreased in 41 states before 2016.

But the increasing frequency and severity of wildfires has offset that progress by “about 25 percent” over the past eight years, said Jienan Li, a researcher specializing in indoor air quality at Colorado State University.

Outdoor air pollutants can affect the chemistry of indoor air, making the air we breathe at home or in the office less healthy, Li notes. Indoor air pollution can worsen asthma and other respiratory problems and lead to “sick building syndrome”, a condition with symptoms such as fatigue, headache and nausea.

As a result, indoor air purifiers are becoming increasingly popular, especially in the US market This is expected to more than double from $2.8 billion in 2022 to $4.78 billion in 2030.

If you are considering purchasing an indoor air purifier, here are some things you should know.

What is an air purifier and who needs one?

Air purifiers are usually portable, mechanical filters that capture fine dust and other particles from the air.

Jill Heins, a senior director at the American Lung Association, doesn’t use the term “air purifier.” Technically, these devices “clean” the air rather than purify it, she says. “Just because air goes through a HEPA filter doesn’t mean it’s free of viruses, bacteria and other germs.” Most home devices can trap virus particles, but generally don’t kill them unless they also use other technology, such as germicidal UV light.

According to Li, air purifiers are most important for people who are sensitive to particles because they have asthma, allergies to pollen or dust, or cardiovascular diseases, but also for children, pregnant women and the elderly. But with an air quality index of 150 or higher“Like when the wildfires in Canada hit the skies in New York and the air wasn’t clear, everyone should consider using an air purifier,” Li says.

How does an air purifier work?

The components of an air purifier are fairly simple: A fan sucks in air from the room and pulls it through one or more filters. The gold standard is a High Efficiency Particulate Accumulator (HEPA) filter. A HEPA filter can remove 99% of particles as small as 0.3 microns, including dust, pollen, pet dander, and some bacteria. Some air purifiers may also contain carbon filters, which are effective at removing odors, gases, and volatile organic compounds (VOCs).

Some units have extras such as germicidal UV or ionizers. The latter became popular in the 80s and 90s to keep dust out of the air, but have since fallen out of favor because they create ozone gas.

The effectiveness of an air purifier depends on factors such as the type of filtration used, the size of the unit in relation to the room (most units will be labeled with how much room they can effectively clean), and the clean air delivery rate (CADR), a measurement that indicates how much air an air filtration system can filter per minute.

Proper maintenance, such as regular filter changes, will keep your vacuum cleaner working effectively. Heins notes that buyers should check the cost of replacement filters before purchasing a vacuum cleaner; sometimes they can be as expensive as the unit itself. It’s a good idea to use air purifiers in conjunction with regular cleaning practices and at least 10 minutes of ventilation per day when outdoor air quality is safe.

Do I need an air purifier if I have an HVAC system?

Air purifiers target finer particles than HVAC (heating, ventilation, and air conditioning) systems and can improve the quality of your air. Li says that people living in a house should aim for one air purifier per floor (though you should still check the unit’s CADR to make sure it can handle the size of your space), while those in smaller apartments can get away with one — just move it to the room where you spend the most time: for example, from the living room during the day to the bedroom at night.

When should I use an air purifier?

You can use an air purifier as often as you like.

If you want to be energy-conscious, track the Air Quality Index daily and use it when the color-coded system moves into the orange zone – an index of about 100 or higher. Based on US Department of Energy estimatesAir purifiers don’t use much energy: about 75 watts, or about as much as a phone charger. You can leave one on all day for about $120 a year.

Some devices have built-in particulate matter sensors, which measure the concentration of particles in the air and start filtering when PM2.5 levels are high. However, such sensors do not focus on ozone, CO2 or VOCs.

Unfortunately, there are few easy, inexpensive, and completely reliable ways to test your home’s air quality, Heins says. “The American Lung Association doesn’t recommend that people routinely test their home environment,” beyond carbon monoxide and radon, both of which can be monitored via a long-term detector in your home, Heins says. Some companies do offer continuous indoor air quality monitoring systems that test for a wide range of indoor pollutants and “give you feedback, usually through a phone app,” she says, though these systems can be expensive and unreliable.

How much does a good air purifier cost?

According to Heins, a good air purifier can cost between $150 and $1,500. You should be able to find an excellent single-room unit for less than $300.

A homemade Corsi-Rosenthal box can also clean air effectively and inexpensively. To make one, you will need four or five MERV13 particulate air filters, taped together to form a cube, and a box fan to pull air through the filters. A 2022 study found that a Corsi-Rosenthal box with five filters had a CADR rate of 600 to 850 cubic feet per minute.

What else can you do to maintain good air quality in your home?

“Don’t burn anything in your home, whether it’s cigarettes, vapes, fireplaces, candles, or natural gas for your appliances,” Heins says. The air quality in your home generally decreases when you cook with gas. If you have a gas stove, make sure you use an exhaust fan while cooking and open a window if the air quality outside is safe.

The fragrance chemicals in cleaning and personal care products can also affect the air quality in your home. Make sure to choose products that are free of harmful chemical compounds to keep your home clean and fresh. Regular dusting and vacuuming removes dust particles and pet dander, and is especially important during wildfires, when harmful polycyclic aromatic hydrocarbon (PAH) particles can settle on furniture and indoor surfaces.