The Best Indoor Air Quality Monitors We’ve Tested for Better Air
To become aware of your indoor air quality index is to enter a realm where the invisible becomes something you can never unsee. Until I wrote about my quest for good air in my Brooklyn apartment, I didn’t know air quality monitors even existed. Now I couldn’t live without them.
We humans evolved to respond to changes in temperature, precipitation, and wind. Bad air is silent and often odorless, but long-term exposure to certain vapors, particulates, and high levels of CO2 can impact cognition and make us vulnerable to certain cancers, as well as heart and respiratory diseases. Reading the daily temperature and looking at weather forecasts prepares us for what’s to come, but checking your air quality might be the biggest step you make in improving your health.
These air quality monitors were tested in two locations: a 130-plus-year-old Brooklyn apartment with a gas stove in a building that is undergoing construction, and a cabin in the Maine woods that uses an electric stove. There were two cats, a dog, and two people during the entire testing period. I had various air purifiers running at all times. Neither location had central air or HVAC with MERV filters, nor did they have over-stove exhaust fans that could remove fumes to the outside. In both locations, it was cooking on the stovetop that produced the worst air. These monitors were used both on days with excellent outdoor air and days when air quality was in the moderate zone, above 50 on the US Air Quality Index.
For more ways to keep your air quality in check, take a look at our guides to Best Air Purifiers and Best Robot Vacuums.
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- Photograph: Lisa Wood Shapiro
Best Overall
AirVisual Pro Indoor MonitorI’ve been using AirVisual Pros for the past five years. My first one only began malfunctioning after four years. Made by IQAir, same maker of the Atem X air purifier, the AirVisual had an easy-read 5-inch LCD display screen. The AirVisual’s graphic of a boy’s face along with the AQI color scale lets me know my indoor air quality from across the room. I don’t have to log on to the internet or open an app to know exactly what is in my air.
The AirVisual has the added feature of giving both indoor and outdoor readings. This saves me the extra step of checking the outdoor air quality on my phone. And it cycles through various displays—it has the time, then it will show both indoor and outdoor readings, along with congratulating me for achieving excellent indoor air quality or it will recommend that I open a window. It’s oddly specific. As the air quality gets poorer, the little boy will stop smiling with a green background and become solemn with a yellow background; finally, if the air is truly dangerous, he’ll put on a gas mask and the color turns dark purple. The AirVisual measures PM 2.5 and CO2, and displays the temperature and humidity. It has an easy-to-read dashboard on the app and keeps data for a year, but its biggest strength is its display, especially when I burn a pizza and the boy gets sad and dons a gas mask.
- Photograph: Lisa Wood Shapiro
Best Display
PurpleAir Touch Indoor Air Quality MonitorWhen that apocalyptic orange cloud set over San Francisco in 2020, the crowdsourced air quality index map PurpleAir was the place to see how bad the air really was. PurpleAir’s Real-Time Air Quality Map is created by the public using sensors that PurpleAir sells. It offers two types of outdoor air monitors: the PurpleAir Classic Air Quality Monitor and the PurpleAir Classic SD Edition, which is able to store data without Wi-Fi. The one I have is PurpleAir's new Touch Indoor Air Quality Monitor. Its simple white oval plastic orb reminds me of a decorative, color-changing night light. The PurpleAir Touch measures PM 2.5. If an air quality monitor can measure only one thing, it should be PM 2.5. PurpleAir uses the same color scale for the US Air Quality Index, or AQI Scale. The Touch’s inner LED ring glows green for good air, yellow for moderate, orange for unhealthy for sensitive groups, red for unhealthy, purple for very unhealthy, and deep violet/maroon for hazardous. Depending on the number of taps of your finger, the glow gets brighter or turns off; it’s adjustable.
PurpleAir told me an app is in the works, but for the moment it's the PurpleAir website that has its “community scientist”-sourced map. I was confused the first time I looked at PurpleAir’s map, because it included both indoor and outdoor monitors. And while there the specific model of monitor pops up when you click the number, I’m not sure if I care that Zoe’s indoor air quality in Brooklyn is awesome or that Zander must have burned his muffins in Queens. I think including the indoor monitor data on the map muddies the user experience. To find out the actual AQI number that the PurpleAir Touch is reading, you need to register your Touch with PurpleAir and view it through PurpleAir's web portal. On its Real-Time PurpleAir Map I can see the circle that’s my Touch. There I can see the numbers for my living room. You can choose to be private or public. Looking at the map, I now want to get PurpleAir's outdoor monitor. And while configuring, registering, and checking a web portal is an extra step, I appreciate the simplicity of the Touch’s color system. The PurpleAir touch also makes a useful night light, though it was too bright for me at its highest setting.
- Photograph: Lisa Wood Shapiro
Best Composite Score
Awair ElementWhen I first used the Awair five years ago, it didn’t bother me that it had its own composite scoring system. The Awair sensor uses a fan and laser sensor to detect PM 2.5; toxic chemicals known as toxic volatile organic compounds, or TVOCs; CO2; temperature; and humidity. Those individual scores go into Awair’s special algorithm that weights each of the five sensors and its actual toxic levels to humans over time, creating its color-coded scoring system. That means a score of 1 is a health hazard while a score of 100 means you’ve reached indoor air nirvana. The issue for me and my more air-aware self is when I see a reading of 100 on an indoor air monitor I think it means the air is bad. Yes, there is a tiny green light indicating overall good air, but still, it is confusing for me.
The score is the default setting on the display and can be easily overridden through the Awair app. By clicking on the gear in the upper right corner, you can change the display from the Awair Score to either temperature, humidity, CO2, chemicals, dust PM 2.5, or a clock. Though, even when I change the display, the indicator light will shine for the Awair score, so right now my PM 2.5 is 4—that’s good—but my indicator light is a confusing orange because of the high humidity that puts Awair’s composite score at a moderate 55. And as for the TVOCs or toxic chemicals, it measures for a mixture as it cannot tease out a specific VOC like formaldehyde or benzene.
- Photograph: Lisa Wood Shapiro
Best for a Desk
QP Pro Air Quality MonitorI can’t help but think the QP Pro Air Quality Monitor was designed to sit on your desk and be used by those with excellent eyesight. I needed my reading glasses to use the touchscreen display. While the QP Pro’s app is easy to read, it’s odd that for a small monitor that does so much—it reads PM 2.5, TVOCs, temperature, CO2, and humidity—requires a wee bit of squinting. The QP Pro’s bright 3-inch Retina display lets you choose the sensor you want to prioritize to a bigger font. So, for example, you can tap the CO2 and that will be the easiest-to-read number. Scroll on the screen and it will display the time, weather, outdoor AQI, and UV reading. And, in case of power outage, its lithium-ion battery has a four-hour life.
While this little monitor does a lot, I found it something I would use on a bedside table or next to my computer. The screen, while crisp and clear, is impossible to read from across the room. Still, for the price it packs a lot in a tiny package.
- Photograph: Lisa Wood Shapiro
Best for Travel
QP Lite Air Quality MonitorI liked the QP Lite Air Quality Monitor more than the QP Pro for the simple reason it had a clear display. And while it’s smaller than the Pro, its lithium-ion battery life is slightly longer at 6.5 hours. The OLED display and color indicator light, utilizing the AQI color codes, are easy on the eyes. And while the Lite doesn’t measure VOCs, it does measure PM 10, PM 2.5, CO2, temperature, and humidity.
The Lite’s ring-box size makes it the perfect Airbnb or hotel room accessory. I recently brought it along with me to a New England wedding and my suitemate and I woke up to CO2 above a thousand. We felt groggy and kept yawning. I opened the windows and we felt better in minutes. This is what an air quality monitor can do. Instead of a vague feeling that you’re getting tired or don’t feel great, one glance at the Lite’s screen and I knew to let the fresh air in. The touch bar at the top of the Lite took some getting used to, but tapping it scrolls through the readings.
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Photograph: Suebsiri/Getty ImagesWhy Do I Need an Indoor Air Quality Monitor?
Air quality monitors vs. air purifiersBy having a stand-alone air quality monitor, you will be able to see whether your air purifier is keeping up with the air in your physical space. In recent years, consumer indoor air quality monitors have improved in accuracy. After time those sensors can clog, giving off incorrect readings. I’ve used a hair dryer, set at the cool setting, to dislodge buildup in the sensors. Still, there seems to be a finite lifespan for the monitors I’ve used, as I’ve yet to have an air quality monitor work beyond four years. When placing or installing a monitor, look for the breathing zone height, around 3 to 6 feet off the floor.
I am still sometimes surprised when I see a poor air quality reading on the monitor. I won’t smell or see anything, but my monitor can sense that there is too much bad air. My building is currently having construction, and on several occasions I’ve seen the PM 2.5 reading go well beyond the safe level. At that point, I crank up the air purifiers. Since I started using both air quality monitors and air purifiers, my allergies—even in the spring—have been less severe. It’s made a difference in the quality of my sleep and my overall health. I no longer burn candles, cook without an exhaust fan, or spray air fresheners in my home, as I’ve seen how they negatively impact my indoor air in real time. Get one, and you might feel the same.
Photograph: Lisa Wood ShapiroThings to Know Before You Buy
What to look forEven though many current air purifier models have built-in air quality sensors, having a designated air quality monitor provides independent assurance. After I became air quality enlightened, I can anticipate ways to mitigate bad air. Using air quality monitors taught me to turn on my kitchen exhaust fan and crank up my air purifier before I turn on my gas stove. In the past, I didn’t think much of a little smoke from cooking. Now I do everything I can to avoid it.
Before you purchase your own indoor air quality monitor, here are some things to know. Sensors on three of the air quality monitors reviewed, the AirVisual Pro, Awair Element, and PurpleAir, all performed well in an independent study. While low cost consumer air quality monitors—let’s say, under $300—are far cheaper than those used by professionals, they are also less accurate and not easily calibrated. I have five air quality monitors in my home at the moment and none are giving the exact same AQI, but they are close.
Consumer air quality monitors use sensors to detect tiny invisible particles in the air and/or other contaminants. Some sensors use light scattering to detect fine particulate matter known as PM 10, like the dust you can see in a sunbeam, and the invisible health hazard, PM 2.5. PM 2.5 is the size that we’re most concerned about, that infiltrates the deepest parts of the lungs and enters the bloodstream.
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