Indoor Air Quality Monitor Buying Guide

They can measure a variety of pollutants, but Bernie Deitrick, CR’s test engineer for air quality monitors, says some are more important to focus on than others. “At a minimum, you want an air quality monitor that measures carbon dioxide, fine particulate matter [PM2.5], and VOCs,” he says. “Those are the most common indoor air pollutants.”

Carbon dioxide is useful to monitor because high levels of the gas can cause mild symptoms of headaches and fatigue. A high carbon dioxide reading can also indicate that not enough fresh air is circulating through your home.

Fine particulate matter called PM2.5 consists of particulates of various substances that are 2.5 microns or smaller in diameter. They can come from many sources, including truck exhaust and wildfire smoke. These particulates can enter your lungs and bloodstream and contribute to a variety of health problems, including heart disease, asthma, and low birth weight.

VOCs are volatile organic compounds that can be found in paints, household cleaners, building materials (such as new carpets), dry-cleaning agents, and more. Exposure to certain VOCs can cause headaches, nausea, kidney and liver damage, and potentially cancer.

Some air quality monitors are also claimed to detect carbon monoxide (CO), but you should use a carbon monoxide detector instead. Exposure to carbon monoxide can be fatal, which is why CO detectors must meet strict safety standards. Indoor air quality monitors aren’t held to such standards and may not detect CO as reliably as a CO detector. For help picking out a CO detector, see our guide to the best smoke and CO detectors.

Deitrick says the best air quality monitor is the one that you pay attention to so you can understand what’s happening within your home and address any air quality problems. To see which models performed the best in Deitrick’s lab tests, see our review of the best indoor air quality monitors, or head over to our detailed indoor air quality monitor ratings.

To evaluate air quality monitors, we focus on four different tests. Our engineers judge how easy they are to use, the number of important air quality metrics they analyze, whether they display some kind of overall air quality score, and how useful their screens are for viewing air quality readings. Our ease-of-use tests judge how well each monitor’s app works and whether it allows you to easily view historical data. We also do a simple test on the sensors on each monitor to make sure they detect particulate matter, VOCs, temperature, humidity, and carbon dioxide. (We don’t evaluate the accuracy of the sensors.) All of these results are compiled into an Overall Score for each model in our air quality monitor ratings.

Our air quality monitor ratings include a $70 model and two models that cost just under $100. All three monitors detected pollutants comparably to the others we tested, which cost as much as $300.

If you’re wondering about the responsiveness of an air quality monitor’s measurements, Deitrick says you can easily test it out yourself. “Try breathing on the monitor,” he says. “Exhaled breath is typically around 4 percent carbon dioxide, or 40,000 parts per million. A monitor that measures carbon dioxide should show an immediate response.”

You can also try shaking a dusty rag near the monitor to register PM2.5 particulates, or open a can of oil paint to detect VOCs. Both readings should increase noticeably.

That depends on the measurement scale your monitor uses. If it reports the Environmental Protection Agency’s Air Quality Index (AQI) score for your community, then lower numbers equal better air outside while higher numbers are worse. But some monitors generate their own air quality score using “school test” scores, where 100 is perfect and anything lower is worse.

Most smart air quality monitors will also indicate whether readings for pollutants, such as PM2.5 and VOCs, are concerning and fall outside of acceptable limits. They may color-code the readings (green is good, red is bad) or describe them in simple terms like good, slightly high, slightly low, normal, etc.

You should put one in the part of your home where you’re most concerned about air quality, such as a room for children or a baby (see CR’s reviews of baby products), or simply where you spend the most time. “Your air quality monitor should live where you do,” Deitrick says. “If you spend all your time in the living room, then place it there.” You may even want to consider buying multiple monitors to place in several rooms that you use often, such as your bedroom, kitchen, and home office.

If you’re looking for a general air quality app to give you your local AQI score and pollutant measurements, your best option is the EPA’s AirNow app. (You can also check your area’s air quality at AirNow.gov.) AirNow aggregates air quality readings from professional air quality monitoring equipment owned by state, county, and municipal governments.

For more, read Consumer Reports’ tips for using AirNow and other resources to monitor air quality and protect your family’s health.