Works by typing one number a day

Airthings Wave Plus

Measures radon too. It has no screen: you read the numbers in the Airthings app.

About $230–$250checked October 2026

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Photo: Airthings

±(30 ppm + 3%)CO₂ accuracy, as the maker states it
Type one numberHow the night gets into HouseExhale
On by defaultSelf-calibration
BatteryTwo AA batteries, about 16 months

At a glance

In its favour: Import whole nights from its CSV
In its favour: Two AA batteries, about 16 months
Worth knowing: Self-calibration on; no off switch documented
Not stated by the maker: Altitude correction not stated

With HouseExhale

The app looks at your bedroom’s CO₂ across the night and checks it against the 800 ppm goal. Here’s how this monitor’s nights get in.

On Android, iPhone or in a browser

Each morning, type the night’s high from the Airthings app, or import its CSV.

Finding last night’s high

Open the Airthings app each morning and look at last night’s CO₂ history. Note the highest point while people were asleep, and type it in the app.

Its export is a CSV the app can import, so you can bring in whole nights instead of typing.

Where to put it: about head height, at least 2 ft from anyone’s face, away from windows, doors and vents, and in the same spot every night. More on placement

Calibrating it

Worth knowing: Self-calibration on; no off switch documentedOn; the maker doesn’t say whether it can be turned off (it treats the lowest reading of the past week as fresh air)

Outdoor air is about 425 ppm. Outside in the shade, a good monitor settles between about 400 and 450 within 15 to 30 minutes. Many monitors treat fresh air as 400, so 400 to 420 is normal. Can I trust my monitor?

Specs

Sensor and accuracy: True CO₂ (NDIR), ±(30 ppm + 3%) after about a week of settling, plus radon
Self-calibration: On; the maker doesn’t say whether it can be turned off (it treats the lowest reading of the past week as fresh air)
Corrects for altitude: Not stated by the maker
Also measures: Radon, VOCs, temperature, humidity and air pressure
CO₂ range: 400–5,000 ppm
How often it updates: Every 5 minutes (radon every 60 minutes)
Power: Two AA batteries, about 16 months
Screen: None; read the numbers in the Airthings app
History: The web dashboard exports up to a year as a CSV
App: Airthings app (free) for iPhone and Android (one of the three latest major versions, with Bluetooth 4.2 or later)
Exports a CSV: Yes
Connects by: Bluetooth LE to the phone app, plus Airthings SmartLink; no Wi-Fi listed. To see live readings from anywhere, and for notifications, it needs an Airthings hub.
Alarm: No sound alarm. Wave a hand in front of it to see a green, yellow or red glow. The app sends notifications when air quality drops, which need a hub; they can be turned on or off.
Smart home: Airthings lists IFTTT, Amazon Alexa and Google Assistant; Alexa and Google only speak the readings, and radon isn’t supported there. Airthings says its monitors don’t yet work with HomeKit or SmartThings. Home Assistant: the official Airthings BLE integration reads CO₂ locally (“Local Polling”) once the monitor is switched from SmartLink to Bluetooth, which stops live readings in the Airthings app. Home Assistant’s cloud Airthings integration is the other route.
Size: 120 mm across × 36 mm tall (4.7 × 1.4 in)
Weight: 219 g (7.7 oz), with batteries
Works in: 4–40 °C (39–104 °F), below 85% humidity (non-condensing); indoors only, away from heavy dust and direct sun
In the box: The monitor, two AA batteries (already installed), a quick start guide, a regulatory booklet, a silica bag and a screw for wall mounting
Warranty: Standard warranty (1 year, or 2 in the EU/EEA, under Airthings’ terms); registering within 30 days of purchase extends it to 5 years

Specs from the maker’s own pages, checked October 12 and October 17, 2026. “Not stated by the maker” means no maker page we could open says.

Turning ventilation up

Home Assistant’s Airthings BLE integration reads its CO₂ over Bluetooth, with no cloud, once the monitor is switched from SmartLink to Bluetooth (that stops live readings in the Airthings app). Home Assistant: Airthings BLE integration

With a smart-home relay on a ventilator’s high-speed input, that reading can turn an HRV or ERV up at 750 ppm and back down at 650. Ventilator makers don’t document this, so check your unit’s manual first, and keep to low-voltage inputs.

CO₂ controls · Make the system you have turn up by itself

Before you buy

Worth knowing: It may no longer be sold by its makerPossibly discontinued at Airthings: its Norway store says “No longer available on airthings.com” (still at Amazon and some retailers) and suggests the View Plus. The Home Depot US still lists it at $229.99 (model 2931). Airthings’ US page couldn’t be opened.
Plain fact: About $230–$250 before tax and shipping$229.99 at The Home Depot, $249.99 at Airthings.

About $230–$250, checked October 2026. Prices change often; we checked at the maker’s store and large US retailers. Any monitor that measures true CO₂ works with HouseExhale, and one is enough: move it between rooms.

Airthings Wave Plus at Airthings (opens in a new tab)

Compare it

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AirGradient ONE
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Shows particles too, with a 24-hour curve on its screen. Plug it in overnight.