Poor indoor air quality causes serious health issues. Things can be improved with determination to sniff out the cause of the problem—and some pricey hardware.

This past winter, I played the role of reluctant shut-in. I was recovering from a health calamity which forced me to spend my days working from a sofa in my den. I had never spent so much time inside my home—a 131-year-old, two-and-a-half-bedroom, fourth-floor apartment in Brooklyn’s Cobble Hill Historic District. I live here with my three children, and we consider ourselves lucky to have nine windows on three exposures. I feel less lucky about the constant hum of the six-lane Brooklyn Queens Expressway one block away, or the hiss of the old-fashioned steam heat system.

I also suffer from a perennial sinus infection that usually shows up during February or March, then blossoms into a full upper respiratory infection before the grand finale: situational asthma that requires two different inhalers; prednisone; and during one particularly bad bout, a nebulizer at urgent care. I wasn’t sure when my yearly scourge would make its appearance, but I was certain it would be soon.

A public relations rep from a company called Airthinx offered me a review unit of its consumer air-quality monitor, which measures indoor air pollution. (I’m lucky to work in technology journalism, where I get to borrow expensive equipment for testing purposes.) I was curious. I never really considered the quality of my air before, and as long as my carbon monoxide monitor and smoke detector didn’t go off, I assumed all was well.

A week later, I opened what looked like a See’s Candy box to find the small, white, plastic Airthinx. I plugged it in and watched a thin beam of red light glow across the top. It wasn’t an alert telling me to set up a Wi-Fi link—the device costs $700 and requires a monthly $30 subscription that, in part, goes toward always-on 3G connectivity. That red light was a warning: I had Poor Air.

The Airthinx uses nine built-in sensors to measure key air quality indicators. There are the obvious ones like temperature, humidity, and carbon dioxide; ones that don’t seem to matter like air pressure and organic compounds; and the ones you don’t think about like formaldehyde and particulate matter. Particulate matter is a catch-all term. It can be dust, smoke, soot, viruses, fungi, or bacteria, among other things. Our nose hairs capture the larger particles measuring down to 10 micrometers in diameter, and instead of breathing those particles into our lungs, we swallow or expel them. It’s the tinier pieces—2.5 micrometers or smaller—that can lodge deep in the lungs. And if the particles are toxic, like bits of dust from asbestos, they can be deadly. The World Health Organization estimates 5 percent of lung cancer deaths can be attributed to particulate matter.

I opened the Airthinx app to see that my Indoor Air Quality score was 72 out of 100. Even though zero is the worst possible score and 100 indicates pristine conditions, 72 ranks as poor? Why? Well, the particulate matter in my apartment measured almost twice the outdoor average for my area of Brooklyn (maybe because I was so close to the BQE?) and the “volatile organic compounds” measured more than three times what the WHO recognizes as “good.” My place was also too hot and too dry, according to the Airthinx.

Vacuuming with my small canister vac only made my PM and VOC levels spike. Plugging in my tiny humidifier didn’t boost the humidity but somehow increased the PM score. I couldn’t get good air, and it was obvious that I was trying the wrong remedies. Meanwhile, the Airthinx silently watched me with its judgy red light.Most Popular


feather duster inhaler and pressure monitor
Photograph: Alex Wallbaum

Not too long ago, our outdoor air was deadly. On Thanksgiving Day in 1966, a thick toxic smog covered New York City, and about 200 people died from inhaling it. After the passage of the Clean Air Act and creation of the Environmental Protection Act in 1970, our air has improved. However, the current administration continues to roll back those emission-curbing protections, and for the first time in four decades, there’s been a 15 percent increase in unhealthy or hazardous outdoor air quality in the United States.

Add to that the effects of climate change, like the wildfires in California, and staying indoors is often the only means of keeping our lungs safe. The environment that has the greatest impact on our health, the one where we spend up to 90 percent of our days, is mostly unregulated and often makes us sick.

It’s where we live and breathe: our homes and offices. Indoor air pollution causes a constellation of symptoms: headaches, fatigue, and low productivity, sometimes referred to as sick building syndrome. “If you think about what we know about healthy living, you’ll go to exercise and a healthy diet,” says Joseph Allen, an industrial hygienist and researcher at Harvard. “So what’s the hole in living a healthy life? It’s our indoor environment. It’s the place we spend the most time. But the big hole exists.”

I can’t help but think of how wellness and technology have merged. I can track my sleep with an app, and I can measure my body mass index with a sensor-laden mirror. And while the Apple Watch can tell when a heart goes into arrhythmia and truly save a life, most newer technologies can just feed us data about a problem while doing little to solve it. As more devices connect with our phones and give us easy-to-digest optics, we can be forgiven for overlooking the chasm between awareness and action. In so many ways, Silicon Valley’s technological innovations fill the same role as the analog scale fills in the life of the dieter. Here’s a problem; now it’s on you to fix it.

Consumer indoor air-quality monitors are ubiquitous in Asia—as common as antipollution face masks. Unlike Asian markets where indoor air-quality monitors are projected to generate $1.7 billion by 2023, the US market for these devices is still nascent.

Even though I was unsure how precise its readings were, I began to view my Airthinx as a modern canary in a coal mine. I took it to my friend Catherine’s apartment, a place of similar vintage, size, and layout, also on the fourth floor. And guess what. She had good air. How was that possible? Catherine pointed to a device resembling a guitar amplifier on the floor, an Austin HealthMate HEPA filter. FEMA gave her the machine after 9/11 because she lived in Tribeca, close to where the towers fell. She changed the filter two years ago and, according to the Airthinx, the little box was doing its job. Maybe good air actually was achievable by means of some simple technology.Most Popular


I called Deborah Bennett, a researcher at UC Davis’ Air Quality Research Center to discuss how to clean up my air. I mentioned how my air score would drop every time I used the stove. “You’ll need to use your range hood and exhaust fan when you cook,” she said.

I confessed that I live in an old Brooklyn building. There’s no hooded exhaust fan over my gas stove. I don’t even have a window fan.

“In California, that would be illegal,” she said. “I’m not sure what it is in New York. You need exhaust. Get a window fan at least. You need to get that air outside.”

I added a window fan to my list. I had also called in a bunch of other hardware to clean up my air: a humidifier, a new vacuum, a sleek and modern air-cleaning device called the Molekule, and a Dyson Pure Hot+Cool, which has both a HEPA and a gas filter along with a built-in air monitor that links to its app. Bennett recommended a Swiss-made purifier called the IQAir GC Multigas. It was, by far, the most expensive of the group at $1,299. Good air doesn’t come cheap, I guess.

I wasn’t convinced the Airthinx was giving me totally accurate readings (there’s no way to effectively calibrate the device), so in an attempt to collect enough data to produce a good average, I called in two more consumer indoor air-quality monitors: the Awair 2nd Edition and the Air Visual Pro, which each cost less than $300.

Also, I spoke with over a half dozen researchers and industrial hygienists for this story, and all of them cautioned about the limitations of these monitors. Brett Singer, an energy technologies researcher at Lawrence Berkeley National Laboratories who recently coauthored a study on consumer indoor air-quality monitors, told me during our video call that these monitors can alert you that something is amiss but not exactly what.

And something was definitely amiss in my apartment. But before I plugged in my army of air purifiers, I wanted to see if there was another simpler solution to getting good air.

Like … plants? I’ll just buy lots of plants! The oft-cited 1989 NASA research paper on the air-purifying properties of plants made me hopeful that I was a few beautifully curated planter boxes away from gloriously clean air. So, I reached out to the folks at online plant retailer Bloomscape and asked them to send over some samples from the company’s suggested list of air-cleaning plants. They sent two, a large lush sansevieria and a medium-size Kimberly Queen fern.

However, I then had a conversation with Garden Myths author and plant expert Robert Pavlis, which filled me with uncertainty. His written work about the media’s misinterpretation of the NASA plant study makes the point that the study itself was done in a tiny chamber a little larger than an air fryer and did not prove that plants actually clean the air of a small room, much less a home. As Pavlis points out, the bacteria in the planting soil used in the NASA experiment also might have cleaned the air in that tiny chamber.

As I discussed my plan and the practical use of houseplants as air purifiers, he mentioned I would need eight plants per room to make a difference. Looking around my 200-square-foot den, I wondered aloud how I would squeeze eight plants in the space.

“No, I didn’t say eight, I said 80—eight-zero,” Pavlis said. “And they would need to be large. A cactus in the corner, that’s not doing much.”Most Popular


I expressed dismay. “Plants will make you feel better, but they won’t clean the air,” he said.

kitchen covered with plants with a gas stove cooking a steak
Photograph: Alex Wallbaum

My technological march continued. One by one, cardboard boxes appeared in my vestibule. I had three types of floor-standing air purifiers: a three-speed double window fan and two small “personal” air purifiers, including the Dyson and the sculptural, Frisbee-like Atem by IQAir. Personal air purifiers are weird—you plop them on the table in front of you, where they blow purified air directly onto your face—but the round and flat Atem is exceptionally alien.

The company even offers a backpack and a battery, so you can take it out in the dirty world. I have yet to bring it on the subway, though that is the one place I most certainly should be using a personal portable air purifier. I couldn’t imagine it getting through airport security so I could use it in hotel rooms, but that too would be an excellent use for it. I also set up the Atem Car purifier, which I hoped might finally kill the smell—half teen boy, half Old Spice—that haunted my Toyota Sienna.

I got in touch with Shelly Miller, an air-pollution researcher at the University of Colorado in Boulder who also happens to own an Airthinx. We showed each other our dashboards on our phones. She looked at mine and told me that a score of 10 for particulate matter is still too high. I didn’t mention that I’ve gotten numbers as high as 500 when cooking burgers on my gas stove.

Shelly shared things she’s done to improve her home’s air. “I now cook on an induction stove top,” she said. “It doesn’t create the pollution that gas does.” I hadn’t thought of that before. “And I tell people to get rid of their rugs.” When you walk on a rug, she said, particulate matter gets thrown back into the air with each footfall.

I took screenshots of both my Airthinx numbers and the Awair monitor, and then I turned on my bagless, HEPA-filtered Dyson stick vacuum. I ran it over my rugs and watched in horror as the canister filled with what looked like fine gray sand. When I was done, I checked the numbers again. Not only had vacuuming not spiked the PM level, but my overall air quality number improved. Unlike my non-HEPA vacuum’s practice of redistributing dust and who knows what else around my apartment, the filtered vacuum lowered the PM level. Also, my carpet looked fabulous.Most Popular


Next, I wanted to get a baseline of my boys’ room at night. By studying monitor data, I noticed that the score in their room plunged between 2 and 5 am, and that it happened several nights in a row. It was if a waft of bad air was somehow being shot into the apartment.

It was only later, when speaking with William Fisk, an indoor environmental researcher at Lawrence Berkeley Laboratories, that I believe I found the cause. While telling him about my newly-installed kitchen window exhaust fan, he interrupted me. If I ran the exhaust fan all the time, he says, I could lower the air pressure in my apartment.

When the air pressure dropped to a low enough point, he explained, contaminated air from another apartment would get sucked in, infiltrating my living space. I finally clicked on the reading in my monitor’s dashboard I had been paying the least attention to: air pressure. In all the places where the steady line on the air pressure graph dropped, my air quality would all of a sudden get worse. In trying to fix one problem, I created another.

pair of cleats with green smoke coming out of the shoe
Photograph: Alex Wallbaum

I started carrying my monitors to my friends’ houses, where testing their indoor air quality became a sort of parlor trick. Over short ribs, I’d tell my friends, who lived in a two-bedroom apartment on the 35th floor of a new luxury rental in downtown Brooklyn, that their formaldehyde level seemed unusually high at 2.108 milligrams per cubic meter. Their overall indoor air-quality score was the lowest I’d seen (28 out of 1,000), so was this high formaldehyde score due to vapors escaping from their wood flooring? My friends were horrified; they have two young children and pay high rent.

Next, I plugged my monitors into the basement rec room of a friend’s brownstone. There, I felt the vibration that my host explained is the nearby subway train rolling by underground. After each passing vibration, we saw the air quality numbers get worse and the levels of particulate matter rise before both would settle again. We saw the pattern happen four times: the vibration of the train, the dip in air quality, the rise in particulate matter, and then the leveling out.

We wondered if it was the vibration itself that was kicking up the particulate matter. Later, one of the scientists I spoke to theorized that subway cars act as pistons when they pass through a tunnel, pushing the air and all the pollutants ahead of them as they approach. My friend’s basement probably had an air leak, and the subway train was pushing dirty air into the house through the basement wall. I emailed my friend giving the possible explanation for her air-quality scores and suggested using an air purifier. (She asked me not to reveal her name for this story; no one wants to air their dirty air.)Most Popular


Finally, it was time to get serious about cleaning up my own air. I had collected baseline readings in my apartment with the windows closed and opened, and with the air filters running on high, medium, and low.

I put an air purifier in every room, making sure the model was the correct size for the space. Air purifier capacity is measured in the cubic feet of air that flows through it per minute, and efficiency is measured in the percentage of pollutants the machine can effectively filter. A highly efficient 40-cfm purifier is the right size appliance for a 65-square-foot room. I figured that I needed about five such purifiers to effectively clean my home.

Armed with my three indoor air-quality monitors, I kept running different air purifiers with the windows open (yes, that partially defeats the purpose, but this is a test), with the windows closed, with a humidifier on, with a humidifier off. Frustratingly, no combination of factors could produce consistent results. If the outdoor air was clean, I would turn off the purifiers, open all my windows, and enjoy a robust cross breeze. If the air outside was poor and it was hot, I couldn’t get good air without also running my air conditioners.

In my old apartment, there was a constant trade-off between temperature and ventilation. And I wasn’t convinced it was practical to keep the purifiers running all the time. Perhaps this is where the monitors come in, to tell us when it’s time to shut the windows and crank up the purifiers.

“Air quality is constantly changing. It’s not static.” Harvard’s Allen says. “Indoors is a dynamic environment, so we need to be dynamic.” Allen says the industry is moving toward autonomous systems to deal with the inherent complexities of controlling indoor air quality. “You’re not going to have to look at the monitor and make an adjustment. Instead you’ll have the monitor on the wall, and it will be able to talk to the filter and make an adjustment.”

The monitors seemed to enable the equivalent of indoor air quality Munchausen syndrome. But overall, they revealed the true filthiness of the air I breathed and, in doing so, forced me to make big changes.

My kitchen now has a dual-fan ventilation system, and the space is far less polluted than it was before the Airthinx arrived. I’m even debating investing in an induction burner so I can stop cooking with gas. I have an air purifier in every room, ready to be switched on whenever it’s needed. And now, when I wake up, I check the air quality before I check the weather.

I also made a full recovery from my illness, and during the time I was stuck indoors, I noticed positive health changes that my mind can only attribute to good air. I slept better when I kept the Dyson personal air purifier running at a low setting next to my bed. And while a yellow dusting of pollen covered the cars on my street this past spring, I didn’t take a single Zyrtec pill to control my allergies—a first for me. My daughter, a fellow allergy sufferer, had an easy spring too. And that dreaded chest cold I get every year, the one that requires two different inhalers and weeks of worry? It never arrived.

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