What raises indoor particle levels?

EPA lists cooking, candles, fireplaces, unvented heaters, smoking and some hobbies.

Does humidity affect readings?

Yes. EPA says high humidity may cause inaccurate readings.

How long do air sensors last?

EPA says some air sensors are only usable for one to two years.

Air quality monitor

By the Life in Good Form editors. Updated 2026-10-15.

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Quick answerA home air quality monitor, or air sensor, directly reads pollutants such as fine particles in the air around it. The EPA says sensors are useful for general information but can report questionable data points, can run systematically high or low, may read inaccurately in very low or high temperatures or high humidity, and gas sensors often lose sensitivity over time. EPA does not endorse specific products or evaluate sensors indoors. Use a monitor to spot changes, such as smoke from cooking or a wildfire, then act on the source.

Our picks at a glance

Indoor PM2.5 air quality monitor with display. Best for: Tracking smoke and cooking particles at a glance. See options on Amazon
Multi-sensor indoor air quality monitor. Best for: People who want particles plus temperature and humidity. See options on Amazon

Compare the picks and what to watch out for

What an air sensor is

The EPA describes air sensors as a class of technology that reads a pollutant in the air directly, is smaller than regulatory monitors, and is often sold at a price that allows more monitoring locations. Designs vary in which pollutants they measure, how data are managed, whether they are weatherproof and how they are powered. Some are stationary, while others are mounted on vehicles or worn.

EPA notes that sensors measure many pollutants but not all of them, and the key question is whether a sensor measures its target pollutant accurately among other pollutants and at the levels you expect.

EPA lists uses such as science education, research, emergency response and measuring local air quality to better understand pollution sources. For outdoor use, it notes that not all sensors are weatherproof and some need an enclosure, and that sensors may be inaccurate enough to need field calibration for more accurate data.

Why particles matter indoors

EPA says particles 10 micrometers or smaller are inhalable, and small particles can get deep into the lungs, with some reaching the bloodstream. People with heart or lung disease, children and older adults may be at greater risk. Studies have linked particle exposure to eye, nose and throat irritation and worsening heart and lung symptoms.

Indoors, EPA lists cooking, burning candles, fireplaces, unvented space or kerosene heaters, smoking and some hobbies as particle sources, along with particles that come in from outside. In homes without smoking or other strong sources, EPA expects indoor levels to be the same as or lower than outdoors.

Limits to know before you buy

Limitation	What EPA says	What to do
Bias	Data may run systematically high or low	Watch trends, not single readings
Weather	Low or high temperatures and high humidity may cause inaccurate readings	Keep it away from humidifiers and steam
Drift	Many gas sensors lose sensitivity over time; some last only one to two years	Check the expected sensor life
Gaps	Sensors may not collect data all the time	Check regularly that it is running

EPA also notes that many sensors do not show data on a screen in real time, so you may need an app or software, and some need WiFi, cellular or Bluetooth. If you want a reading at a glance, look for a built-in display.

EPA does not rate products

EPA says it cannot recommend or endorse particular commercial sensors. Its scientists publish performance evaluation reports on some sensors, but these are generally done outdoors, and EPA says it does not evaluate sensors in indoor conditions. It points to other groups, including Lawrence Berkeley National Laboratory and NIOSH, that have tested sensors indoors.

EPA's Enhanced Air Sensor Guidebook, updated in 2022, includes a checklist for selecting sensors and a short infographic of questions to ask before you buy a lower-cost air sensor. Reading a sensor's evaluation results and user manual before buying is a better guide than a marketing claim.

Using readings to lower indoor particles

When your monitor shows a spike, EPA's steps to reduce indoor particles include:

Vent fuel-burning appliances such as stoves, heaters and furnaces to the outdoors.
Use an exhaust fan vented outside when cooking.
Avoid unvented stoves, fireplaces or space heaters indoors.
Have heating systems, flues and chimneys inspected and cleaned each year.
Change heating and cooling system filters and air cleaner filters as the maker directs.

For humidity, which can also affect sensor readings, see our dehumidifier guide and humidifier filters guide.

Placement tips

Because EPA says high humidity can cause inaccurate readings, keep a monitor away from humidifiers, kettles and showers. Place it where you spend time, such as a bedroom or living room, and away from direct sources like the stove if you want a room-level reading. If you also want protection on smoke days, see our KN95 and N95 mask guide.

What to look for when you buy

Indoor PM2.5 air quality monitor with display

Best for: Tracking smoke and cooking particles at a glance

EPA notes many sensors lack a real-time screen; a display avoids needing an app.

Watch out: Readings can run high or low; watch trends.

See options on Amazon

Multi-sensor indoor air quality monitor

Best for: People who want particles plus temperature and humidity

Humidity readings help explain sensor errors EPA links to high humidity.

Watch out: Gas sensors may lose sensitivity over time, per EPA.