A calm CO₂ monitor
Air the Room watches the air in a room and tells you, quietly, when it needs fresh air, for about how long, and when you can shut the window again. No screen. No account.
One email when the first batch is ready. Expected price $99–129. Privacy
Why it matters
Every breath adds a little CO₂. Outside air sits around 425 parts per million. Two people asleep in a small bedroom with the door shut can push it past 2,000 by morning, and you can't smell it. Ten minutes with the window wide open brings it back down.
In student bedrooms, opening a window brought average CO₂ overnight down from 2,585 to 660 ppm. With fresher air, sleep measured better on a wrist monitor, and the next day students felt less sleepy, concentrated better and did better on a logical-thinking test.1 A Dutch study found deeper sleep with just a window or the bedroom door open.2
In a Harvard study, office workers' decision-making scores were 15% lower at about 950 ppm and 50% lower at about 1,400 ppm than on days with plenty of outdoor air.3
Office workers given less outdoor air took about 1.5 times as much short-term sick leave.6 CO₂ shows how much of the air you breathe was already breathed out by someone else, and with it the risk of catching colds and flu through the air.7
Germany's Environment Agency rates indoor CO₂ below 1,000 ppm as harmless, 1,000 to 2,000 as elevated, and above 2,000 as unacceptable.8 That's why Air the Room alerts at 1,000.
What it does
One alert, with how long to keep the window open. A short, wide-open airing swaps the air in minutes; Germans call it Lüften, online it's house burping. It learns how fast each room clears, and suggests a shorter airing when the air outside is poor.
The part most monitors skip. Close up before the room cools down, or the street noise gets in. Nothing else: no scores, no streaks, no daily tips.
Calm by design
A soft glow in green, amber or red. It dims at night, or stays dark until a room needs air.
No beeps or alarms. It tells your phone or Mac, once.
Nothing to sign up for. Plug it in and your devices find it.
Your phone, Mac and browser read the monitor straight over your Wi-Fi. Readings never leave your home.
Where you'll see it
Widgets for the Home Screen and Lock Screen, and an app with each room's day and week.
Every room in the menu bar. Click for its full history. Alerts come from your Mac itself.
The monitor serves its own page on your home Wi-Fi, not the internet, so a Windows PC or an Android phone at home can see it too. Android apps come later.
How it compares
| Feature | Air the Room | IKEA ALPSTUGA | SONOFF AirGuard CO2 | Airthings Wave Enhance | Aranet4 Home |
|---|---|---|---|---|---|
| Price (US) | $99–129 expected | $29.99 | $49.90 | $128–160 | About $200–250 |
| Screen | None, one soft light | Small screen and a light | Screen, color lights and a buzzer | None, a light on tap | E-ink screen |
| CO₂ sensor and rated accuracy | Photoacoustic NDIR (Sensirion), ±(50 ppm + 5%) | Thermal conductivity (Sensirion SEN63C), ±(100 ppm + 10%) | NDIR, ±(50 ppm + 5%) | NDIR, ±(50 ppm + 5%) | NDIR, ±(30 ppm + 3%) |
| Connects | Wi-Fi, no hub needed; readings never leave your home | Thread; your phone needs a Thread hub, about $100–140 more (HomePod mini, IKEA DIRIGERA) | Wi-Fi (Matter) | Bluetooth; seeing it away from home needs an Airthings hub, about $150 more | Bluetooth only |
| Account | None | None (Apple or Google Home) | eWeLink account for its app; eWeLink's data centers are in Beijing and Singapore | Airthings account | None |
| Power | USB-C, soft 2 m (6.5 ft) silicone cable included | USB-C; cable and adapter sold separately | USB-C | 2 AA batteries | 2 AA batteries |
Prices and specs from each maker's listings, privacy policies and published reviews, November 2026. Product names are trademarks of their owners.
Trustworthy numbers
Many cheap monitors estimate CO₂ from other gases, and wrong readings are the most common complaint about this kind of device. Air the Room measures CO₂ itself with a Sensirion photoacoustic sensor, rated within ±(50 ppm + 5%). Each unit is checked before it ships, and it keeps itself calibrated without anything for you to do.
Setup
The details
Designed and assembled in USA using global parts.
| Measures | CO₂, temperature, humidity |
|---|---|
| Size | About 40 mm (1.6 in) across, with a weighted base |
| Light | One soft color light; dims at night, or turns off |
| Power | USB-C, always on; soft 2 m (6.5 ft) silicone cable, USB-A to USB-C, included |
| Connects | Wi-Fi, no hub needed. Readings never leave your home |
| Internet | Only for updates, and for iPhone alerts if you turn them on |
| Works with | iPhone, Mac, any web browser; Android apps later |
| Account | None |
| Price | Expected $99–129 |
No. It's a guide for airing your rooms. It isn't a medical device, and it doesn't detect carbon monoxide, smoke or gas leaks.
Readings never leave your home: they go straight from the monitor to your devices over your Wi-Fi. The monitor goes online only to fetch updates and, if you turn on iPhone alerts, to send each alert through our relay to Apple, which passes it on and keeps nothing. The optional outdoor air check is done by your phone, with your approximate, city-level location.
Staying plugged in lets it measure every 30 seconds and keep your widgets live all day. A battery version would need a hub or a cloud service in between.
Each room gets its own monitor, and every room shows up on your phone and Mac. Turn alerts off for rooms you only want to glance at.
Short, wide airing loses far less heat than a window left cracked open all evening. That's why it tells you when to close it.
We're building the first small batch now. Leave your email and you'll hear first, once, when it's ready.
We're making a small first batch. You'll get one email when it's ready, and nothing else.