The howling winds are like nothing I've heard as they churn the eerie, smoke-filled sky above my community. Nearby, a massive wildfire rages. Disaster is imminent.
In our second-story apartment, my partner and I pack up our most essential belongings and a few treasured possessions. We tape our window seams to prevent smoke and ash from blowing inside and keep our eyes glued to a map of the fire's spread.
The rising stress and deteriorating air quality are too much. We head 20 miles south to a hotel, where we stay until the fire is more contained. Even there, we see ash rain down from the sky.
I live in Pasadena, and my apartment was just outside the evacuation zone for the Eaton Fire, which took 19 lives and destroyed over 9,400 structures in January 2025. That month, the Eaton and Palisades fires raged simultaneously across Southern California, becoming the second- and third-most destructive wildfires in state history.
We were lucky, as the fire's spread stopped five miles from our apartment. While many lost their homes, we were able to return to ours. Still, our taped-up windows did little to keep ash and smoke from seeping through cracks and coating everything in our apartment.
With unhealthy outdoor air quality, we couldn't open windows for fresh air, so we relied on our air purifier. At the time, we had just one in our living room. We've since added another to our bedroom, along with two air quality monitors in each area.
The atmospheric dangers haven't gone away: As I write this piece, smoke from a Boyle Heights warehouse fire is blowing toward us, making it once again ill-advised to open windows.
Fires are a significant contributor to poor air quality, but they aren't the only one. Power plants burning fossil fuels spew pollutants, as does car exhaust from highways and city streets. There's a reason why our phones' weather apps report each day's air quality index, or AQI. And although overall outdoor air quality in the US has improved over the decades, it hasn't gotten better everywhere, especially in communities of color.
We face breathing dangers indoors as well, from gas-burning appliances and furnaces to myriad household chemicals and the off-gassing from furnishings and other goods. Outdoor air pollution slithers inside.
As a health and wellness writer for 12 years, I've often seen concerns about the health risks in the air we breathe 12 to 20 times per minute take a backseat to more tangible human needs, such as crystal-clear water and food free of contaminants. But there are simple steps we can take to improve the air quality in our homes.
Air purifiers can protect our airways from certain contaminants, as CNET Labs has found, but they aren't the best or sole line of defense against poor air quality.
Air purifiers look a lot like speakers — rectangular or cylindrical electronic appliances under 3 feet tall, with perforated metal or plastic casings. You'll typically find them on the floor or a tabletop in high-traffic areas like the bedroom, living room or kitchen. Prices for air purifiers can range from $50 to $1,000.
I didn't grow up in a home with air purifiers, but my mom now has two in her New York suburban home. She'd been relying on her HVAC system's filter, but when COVID-19 cases spiked during the pandemic, she invested in air purifiers.
Experts from air care tech companies like Dyson, Blueair, Airthings, Coway and Oransi all tell me they've seen air purifier sales grow during events that spur concern about the impact of what's in our air on our health. Think the COVID-19 pandemic, wildfires, smoggy days of urban pollution and allergy season.
My colleague Tara Brown, CNET social media manager, recently got her first air purifier. It wasn't technology she grew up with, and at first it seemed like a luxury item.
“The way my mom dealt with a dusty house was to open up the windows when cleaning, and during pollen season we'd try to keep windows closed and take daily allergy pills,” Brown, who lives in the suburbs on the East Coast, says. “As I get older and now have my own money, I am interested in trying one out because I'm allergic to dust and pollen.”
Turns out, Brown's mom was right to open her home's windows. As I've learned, that's the second step you should take when addressing poor air quality, even before turning on an air purifier.
Your first line of defense is to focus on controlling the source of pollution.
“In cities, the largest source of volatile organic compounds used to be vehicles, but vehicles have gotten cleaner, and over time, now it seems that the largest source is actually the stuff we use in our residences,” Linsey Marr, a university distinguished professor in Virginia Tech's Department of Civil and Environmental Engineering, tells me.
This includes common goods like shampoo, lotion, hairspray, deodorant, cleaning products and paints.
If you're looking for low- or no-cost methods to control VOCs, Brigit Hirsch, press secretary for the US Environmental Protection Agency, recommends carefully following product instructions to ensure that you don't use more than is recommended and to determine the type of ventilation required. If you're painting walls, for instance, you should keep your windows open.
As for gas and particle pollution released when you're cooking on the stovetop or in the oven, turn on your range hood to exhaust it. If your range exhausts outdoors, avoid using it on days when outdoor air pollution is high. Instead, an air purifier near the stove can help trap those cooking particles and, if it has an activated carbon filter, some gases.
To remove particles on surfaces before they're disturbed and end up in the air, regularly vacuum with a filtered vacuum cleaner and dust with a damp cloth. To dampen that cloth, use low-toxicity cleaners, like soap and water, that don't contain ammonia or chlorine, which can worsen air quality.
“The most important thing to do about air pollution is source control, so let's actually reduce the sources that are causing the pollution first and foremost,” Glory Dolphin Hammes, CEO of IQAir North America, tells me. IQAir is the world's largest free, real-time air-quality monitoring platform and also sells air purifiers.
Once you've exhausted your options for source control, it's time to ventilate. To prevent pollutants from building up inside, open your windows, turn on kitchen or bathroom fans that exhaust outdoors and use window or attic fans.
When ventilation isn't an option because of high outdoor air pollution, such as during a wildfire or during rush hour if you live near a high-traffic road, you'll want to focus on air purification.
You may be surprised to learn, as I was, that your HVAC's filters were originally designed to protect the system's heating and cooling coils, not human health.
On top of that, Theresa Pistochini, co-director of engineering at the UC Davis Energy Efficiency Institute and Western Cooling Efficiency Center, tells me that to save energy, household HVAC systems usually only turn on when heating or cooling the air, so the fan doesn't run constantly. That means it's not filtering your air all the time, and even when it does, you might not have the highest-grade filter.
You'll want to pay attention to MERV, which stands for minimum efficiency reporting value and is based on a test method developed by the American Society of Heating, Refrigerating and Air Conditioning Engineers. While most people buy cheaper MERV 8 filters for their HVAC systems, they should be getting MERV 13 to improve their air quality.
An HVAC filter's MERV rating indicates how effectively it removes airborne particles of different sizes.
“In order to get a certain MERV value, you have to be able to remove a certain percentage of particles,” Pistochini says. “The higher the MERV rating, the higher the fraction of the particles that are removed.”
Even so, a HEPA (high-efficiency particulate air) filter, which is the highest-grade filter and what you should look for in an air purifier, is best because it removes at least 99.97% of particles that measure 0.30 microns and larger. However, a HEPA filter isn't recommended for HVAC systems because its dense nature creates too much airflow resistance. That's why a MERV 13 filter is used instead, and it removes at least 50% of particles sized from 0.30 to 1.0 microns, with the percentage increasing as particle size increases.
Note that neither removes gases – for that, many air purifiers have an activated carbon filter, which is just one step in the filtration process.
Since it's more efficient to run a portable air purifier than it is to run an entire HVAC system through ductwork that's prone to leakage and can contribute to energy losses, Pistochini says it's better to use air purifiers right in the room — especially in the kitchen, where you cook, and in your bedroom, where you tend to spend extended periods of time.
But if you're wondering whether you should upgrade your HVAC filter to MERV 13 or purchase an air purifier with a HEPA filter, Joseph G. Allen, director of Harvard's Healthy Buildings Program and a professor at the Harvard T.H. Chan School of Public Health, tells me that you should do both, as they're not significant expenses. Plus, they come with important health benefits.
“Air purifiers solve a key problem, and that is the general low to nonexistent filtration in homes,” Allen says. “Most of the filters that are in a home are low-grade and are designed to protect the equipment. Air purifiers have filters that are designed to protect people. That's a key distinction.”
At the national level, a key element in achieving better air quality is the sweeping government regulation known as the Clean Air Act of 1970. A landmark achievement of the environmental movement, this law requires state, local, tribal and federal agencies to work together to clean our air.
As a result, “air quality in the US has improved tremendously over time, particularly in the last 20 years,” Hirsch says.
According to the EPA's 2025 Our Nation's Air report, since 1970, the combined emissions of benchmark or “criteria” pollutants have decreased by 79%. Using monitors across the US, the EPA measures six criteria pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter and sulfur dioxide.
But while the Clean Air Act has improved our overall outdoor air quality, poor air quality remains an invisible guest in our own homes.
“Hundreds of thousands of lives have been saved [because of the Clean Air Act],” says Allen. “But that is solely about outdoor air pollution. Our indoor air pollution has continued to worsen. We do not have a Clean Indoor Air Act.”
Inside our homes, we're exposed to volatile organic compounds emitted as gases from everyday items such as cleaning products, upholstered furniture and cosmetics. We're enveloped by particulate matter from cooking and burning candles, along with biological contaminants such as pollen, mold spores, pet dander, viruses and bacteria. At the flick of a switch, gas stoves and unvented kerosene and gas space heaters release carbon monoxide and nitrogen dioxide. Through windows and doors and hidden cracks in our homes, outdoor air pollution seeps inside.
At the same time, our buildings have become more airtight. On the positive side, this prevents energy losses; on the negative side, pollutants get trapped indoors once you shut your windows.
While data on indoor air quality is elusive, our outdoor air quality is something we can measure, track and easily view in our weather apps. And despite the Clean Air Act, we still can't escape pollutants in the air we breathe once we step outside our homes, especially in specific neighborhoods.
“Just because air quality got better for a while overall doesn't mean that the air in your community is better, especially if you have a highway, warehouse or power plant nearby,” Laura Kate Bender, the American Lung Association vice president of nationwide advocacy and public policy, tells me.
Since 2000, the ALA has released an annual State of the Air report. In its 2026 report, the ALA found that more than one in four Americans, 152.3 million people, live in locations with unhealthy air pollution levels. Perhaps even more alarming is that almost half of American children, 33.5 million people under the age of 18, live in counties with a failing grade for at least one air pollution measure.
A person of color is also more than twice as likely as a white person to live in a place with a failing grade for all three pollution measures. Hispanic people are more than three times as likely.
Climate change has started showing up in the ALA's reports, “and it's undoing some of the progress that the country made in cleaning up those polluting sources,” Bender says.
A majority of the experts I spoke with mentioned wildfires, which are escalating because of climate change. NASA reports that wildfire activity has more than doubled worldwide over the last 21 years. Its satellites detect active wildfires twice per day.
Because of wildfires, there's been an increase in particulate matter, says Priyanka deSouza, assistant professor in the University of Colorado Denver's Department of Urban and Regional Planning. Research also suggests that levels of ozone, a highly reactive gas that's both natural and manmade, will increase due to higher temperatures and wildfires.
“It isn't looking great,” deSouza says.
In February 2022, the United Nations Environment Programme reported that extreme fires across the globe will increase by up to 14% by 2030, 30% by the end of 2050 and 50% by the end of the century.
A series of proposed and finalized rollbacks of air pollution limits on gas and coal power plants and cars by the Trump administration has undercut progress toward clean air. The EPA's Hirsch says the agency is committed to clean air protections.
Poor air quality has unmistakable immediate effects: difficulty breathing, coughing, irritation of the eyes, nose and throat. Some people may also experience headaches, dizziness, fatigue and chest pain.
As for long-term exposure to polluted air, it has been linked to lung damage, higher risk of respiratory infections, chronic diseases like bronchitis and chronic obstructive pulmonary disease and even cancer. Elevated levels of some air pollutants can raise the risk for heart attacks, strokes, irregular heartbeats and hypertension.
Children are more susceptible to the health effects of poor air quality because their lungs haven't fully developed, Srikanth (Sri) Nadadur, branch chief for the Exposure, Response and Technology Branch at the National Institute of Environmental Health Sciences, tells me. The same goes for older adults, due to compromised lung function and the higher probability of them having a lung disease like asthma or COPD.
Those with hay fever, heart conditions and pulmonary fibrosis (scarring in the lungs) are also more likely to be affected as air quality in the home decreases, according to Dr. Brian W. Christman, an American Lung Association national spokesperson.
Wildfires, in particular, can change how kids' lungs develop. They're also linked to premature death, heart disease, stroke and lung disease.
Airborne pollutants can cause health problems affecting different parts of the body, including the lungs and heart.
Because of their size, ultrafine particles can get deeper into the lungs and then release anything they've absorbed along the way, like VOCs. If these compounds get into the lungs' fluid, they can enter the circulatory system, potentially affecting cardiovascular function.
“Of late, the literature is indicating this having effects on the brain and also on the reproductive system,” Nadadur says. “There is good evidence from multiple epidemiological cohorts for an increase in the incidence of lung cancer from long-term exposure to outdoor PM2.5 particles, but the association for other cancers is still not clearly well known.”
If you're living in a place with poor air quality or have been affected by a wildfire, you should reach out to your doctor if you notice symptoms such as shortness of breath. If you have a lung disease like asthma or other health conditions that a wildfire could worsen, it's important to plan for these events, especially as they become more common. Ensure you have your medication ready and know what to do if an evacuation is mandated.
As for poor indoor air quality, remember the three steps to address it: Source control, ventilation and air purification.
An air purifier uses its fan to draw air inside it, where it passes through various filters to trap airborne pollutants. The freshly filtered air is then pushed out to circulate throughout the room.
Each filter is designed to capture different sizes and types of pollutants. Chloe Waller, Airthings chief commercial officer, explains that a well-designed air purifier filter system works in three stages.
Usually made of fabric and designed to extend the life of the other filters in the system, this outer filter is coarse to capture larger particles, such as pet hair, lint and visible dust. Certain units make this filter washable or vacuumable.
HEPA filters can capture microplastics and certain nanoplastics, dust, pollen, mold spores, some bacteria and viruses and PM2.5 particles, which can come from wildfire smoke, cooking, using a fireplace, vehicle exhaust and industrial pollution.
CNET's 2025 lab tests conducted in a smoke chamber confirmed that air purifiers with a true HEPA filter can capture viruses that might cause illness, including influenza and the COVID-19-causing SARS-CoV-2.
Out of 12 models tested, CNET Labs found that on a low fan setting, the Shark HP232 air purifier performed the best at removing fine particles 2.5 microns and under, averaging 1 minute and 15 seconds. At high fan speed, the Coway Airmega 400S was the best at removing fine particles in an average of 34 seconds.
While HEPA captures particles, an activated carbon filter targets gases such as VOCs and odors from smoke, pets and cooking. Peter Mann, CEO of Oransi, creator of CNET's “best for pet hair and dust” air purifier, added that activated carbon filters can also absorb gases such as ammonia, formaldehyde and hydrogen sulfide.
While activated carbon filters can remove ozone, the efficiency of this process depends on the amount of activated carbon in the filter. However, there is no performance rating system for filters designed to remove gases.
But there is a rating system for particles: clean air delivery rate. The higher the CADR, the larger the area an air purifier can filter.
“My rule of thumb is you want to have 300 CADR for every 500 square feet,” says Allen. “Depending on the exact size of your room, we're trying to target four, five or six air changes per hour.”
Air purifiers can have multiple filtration layers that capture particles and gases.
While many air purifier manufacturers will put the room size on their packaging, they may not display the CADR. That means the air purifier might not be effective unless you're using it in a room smaller than what's noted on the product package.
After all, your air purifier can't filter what it can't catch, which is why you'll want to make sure it's correctly sized for your space. Harvard's Healthy Buildings Program has a sizing tool for that.
“Most consumer purifiers are designed for rooms up to 500 to 600 square feet,” says Waller. “In larger open spaces, or when doors and windows are regularly opened during a smoke event, a single unit running on auto mode may not maintain clean air throughout the space.”
You'll also want to ensure that your air purifier has a true HEPA filter, not one labeled HEPA-type or HEPA-like.
Changing both the HEPA and activated carbon filters is crucial. Collected pollutants build up and clog the filters, and dirty filters can actually release them back into your home, making air quality even worse than it was before you set up your air purifier.
Air purifiers capture airborne particles and some gases as air passes through the machine, which means anything they remove must first be suspended in the air and drawn into the purifier.
There are a few things they can't fully address: “Dangerous gases like carbon monoxide and radon require dedicated detectors and professional remediation,” says Nedra Ogden, senior product manager at Blueair, maker of CNET's top-recommended air purifier.
Radon is an invisible, naturally occurring radioactive gas that enters homes through cracks and gaps from the ground as radioactive metals break down in soil, rocks and groundwater. Carbon monoxide is also an invisible gas, and sources include gas stoves, leaking chimneys and unvented kerosene and gas space heaters.
Air purifiers can't capture the carbon dioxide we exhale, either.
“When you don't have appropriate ventilation, with lots of people breathing, carbon dioxide levels can increase, and it can lead to people getting migraines and headaches,” says deSouza.
Although activated carbon filters can absorb VOCs, there is a limit, especially if they become saturated and aren't regularly replaced.
Air purifiers also can't address temperature and humidity. While they can capture moisture-loving mold spores floating around in the air, Petra Oman, vice president of marketing at home and air care tech company SharkNinja, tells me that these products can't remove mold growing on surfaces or fix a widespread mold problem in your home. For the latter, the EPA recommends a professional mold remediation service.
To determine whether your air purifier is effective, experts recommend investing in an air quality monitor. The one I have in my living room measures radon, PM2.5 particles, CO2, VOCs, air pressure, humidity and temperature.
Zooey Liao/CNET/AirthingsSome air purifiers have a built-in air quality monitor, so the purifier automatically adjusts its speed to match the level of certain pollutants. Yet, air purifiers may not display the pollutant numbers like a dedicated monitor, and will only show pollutants around the machine – not in the entire room.
“It's a classic business maxim: What gets measured gets managed,” says Allen. “If we don't know what the levels are out there, we don't really know what we're trying to manage.”
Beyond a true HEPA filter, you don't need any fancy air purifier features.
Air purifiers that tout UV light filters or ozone- and ionic-producing technologies can do more harm than good because they produce ozone, a pollutant that can worsen airway inflammation and exacerbate asthma and hay fever.
Because of this, in 2008, the California Air Resources Board enacted an air cleaner regulation to limit ozone emissions from indoor air cleaners, requiring the board to certify all indoor air cleaners sold in the state.
“There is a lot of marketing spin with air purifiers,” Mann says. “I believe this is partly because consumers cannot see what an air purifier removes from the air.”
Eventually, air purifiers may have more built-in sensors that adjust speed in real time to capture more pollutants, so a separate air quality monitor wouldn't be necessary.
We could at some point see air purifiers connected to HVAC systems and other smart home and health devices, so that all technologies — cooling, heating, humidification, air quality, health — can work holistically to create a healthy environment. This would help connect indoor air quality to sleep, productivity, illness and other health vitals.
Air purifiers might even get built into walls, furniture and lighting rather than being standalone appliances, according to Gil Jung, director of Coway USA, maker of CNET's favorite air purifier for the whole home.
“AI-driven predictive purification is also a possibility, so rather than reacting to pollution, systems will anticipate it,” says Waller. “Imagine a purifier that precharges to boost mode when it detects from external data sources (air quality forecasts, local wildfire tracking) that conditions are about to deteriorate.”
Your air purifier would turn on before you even smell smoke.
Stuart Thompson, senior design manager of environmental care at Dyson, tells me that we'll see innovation in filtration systems, going beyond HEPA and activated carbon, with “multiple specialized layers to target an even broader range of pollutants.” They'll be able to capture ultrafine particles, absorb more complex gases and break down certain pollutants at a molecular level.
Though true HEPA filters currently aren't reusable, according to Hirsch, research points to reusable filtration systems being a future product development.
Once the air makes its way through these filters, motion sensors could direct purified air toward people based on where they are in a room. Thompson expects future air purifiers to project air farther and circulate it more effectively in larger spaces, so that every corner of the room gets clean air.
It would be great to see air purifiers that produce less noise, which might encourage more people to use them.
According to CNET Labs' 2025 testing, on a low fan speed, the quietest air purifier was the BlueAir 311i at 34.84 dBA. At high fan speed, the quietest model that still effectively filtered particles measuring 0.30 microns was the 51.56-dBA Shark HP102. That compares with about 60 dBA for people speaking 3 feet away.
But while we await the air purifiers of the future, there's still significant work that can be done to prevent future generations from having to worry about air pollution in the first place.
While air purifiers can improve indoor air quality, there's only so much we can expect from a device when it comes to addressing air pollution as a whole.
“Until we stop burning fossil and other harmful fuels for our energy, transportation and production, we're essentially trying to make the health impacts as least bad as possible, but we're not actually stopping them,” says Bender.
Education and awareness are key. Just like you monitor the weather, you should monitor your air quality, both inside and out. Not simply to know when you should remain indoors, avoid outdoor ventilation or turn on your air purifier, but also to see the problem firsthand, as I did during the Eaton Fire.
The air pollution problem goes beyond what any one household can address, meaning collective action is needed. This will require contacting policymakers, whether you're reaching out to your school board, city council, state representatives, federal agencies or the White House to share your stories and thoughts about air pollution and climate change in an effort to push for change.
Just like you wouldn't drink a glass of dirty water or eat food visibly covered in microplastics, you shouldn't have to breathe polluted air. After all, breathing isn't optional. Breathing clean air shouldn't be, either.
Video Producers | Owen Poole, Dillon Lopez
Director of Content | Jonathan Skillings
