Where to Place an Air Quality Monitor (Room by Room)

The core rules

From Airthings' and Atmotube's placement guidance and EPA's Citizen's Guide to Radon.

Rule	Why	Source
Breathing height: about 3.6 to 5.6 ft (1.1 to 1.7 m)	Measures the air people actually breathe	Atmotube; Airthings says approximate breathing height
Lower, at eye level or slightly below, where people sit	Seated breathing height is lower	Atmotube
At least 3.3 ft (1 m) from operable windows, air filters and supply diffusers	Outdoor air or cleaned air skews readings	Atmotube
Not close to a vent or window	Same reason	Airthings
On a solid surface or wall-mounted	Stable sensor conditions	Airthings
Out of direct sunlight	Heat skews temperature and some sensors	Atmotube
Not next to an emission source	Reads the source, not the room	Atmotube
In regularly occupied rooms	That is where exposure happens	Atmotube; EPA for radon

Room by room

Bedroom

Put the monitor on a dresser or shelf a few feet from the bed, not on the nightstand right beside your head, where your breath will push CO2 up. Keep it away from the window and any heating vent. If the display lights up, choose an e-ink or screenless model. See why CO2 matters.

Living room

A bookshelf or side table at chest height in the middle of the room works well. Keep it at least 3 feet from the air purifier, or it will read the purifier's clean outlet air instead of the room. If you want to test the purifier, compare readings with the purifier off and then on, from the same spot.

Home office

Place it an arm's length or more from where you sit, at or a little below eye level, so it reads the room rather than your exhaled breath.

Kitchen

Only if you want to see cooking spikes. Keep it away from the stovetop and oven, where heat, steam and grease distort readings; Atmotube suggests a slightly higher placement (about 5.6 feet) in kitchens. For a whole-home picture, a monitor in an adjoining room shows how far cooking smoke spreads.

Basement

This is where radon is tested (see below) and where humidity matters most. Keep the monitor off the floor and away from the dehumidifier's exhaust. Airthings says monitors with a radon sensor should avoid damp environments above 85% humidity.

Nursery

Across the room from the crib, out of reach, away from the humidifier and window. See air quality monitors for a nursery.

Radon: EPA's placement rules

EPA's Citizen's Guide to Radon gives specific instructions for test placement:

• The lowest lived-in level of the home: the basement if it is used often, otherwise the first floor.
• A room used regularly, such as a living room, playroom, den or bedroom, but not the kitchen or bathroom.
• At least 20 inches above the floor, where it will not be disturbed.
• Away from drafts, high heat, high humidity and exterior walls.
• For a short test of 2 or 3 days, windows and outside doors closed at least 12 hours before and during the test.

A digital radon monitor follows the same rules. See the radon detector guide and the best radon detectors.

Give it time after you move it

Some sensors need time to settle in a new spot. Airthings says the View Plus needs up to 7 days to calibrate its VOC and CO2 readings and states radon accuracy of ±10% after 7 days. Awair says the Element's VOC sensor needs 24 to 48 hours. Atmotube recommends about 12 hours in fresh air after first using the PRO 2's CO2 sensor. Particle readings respond within minutes, so a PM2.5 comparison between rooms can be quick, but judge CO2, VOC and radon only after the settling period.

Common placement mistakes

• On the windowsill. Reads outdoor air, sun and drafts.
• Next to the purifier. Reads the purifier's clean air and makes the room look better than it is.
• On the desk in front of your face. CO2 jumps every time you breathe toward it.
• Above a heating vent or radiator. Temperature and humidity readings swing with the heating cycle.
• Inside a cabinet or behind books. The fan cannot draw room air.
• On the floor. Dust and drafts at floor level are not what you breathe standing or sitting.

One monitor or several?

Start with one in the bedroom, the room you spend the most continuous hours in. Move it to the living room, office and basement for a few days each to learn their patterns. A second monitor is worth it if you want to see how cooking or smoke spreads, or to keep an eye on radon in the basement permanently. For picks, see the best air quality monitors and our explainer on how monitors work.