The device
Always on. Glance-and-go. Twelve signals, one color language. The screen is your at-a-glance answer; the underglow is the across-the-room answer.
Why it matters
You breathe indoor air more than anything else.
You can see the weather outside. Inside, where you spend most of your life, the air is invisible, and usually worse. Terrestream makes it visible.
- 90% of your life is spent indoors, breathing the same air EPA
- 2-5× indoor air can be more polluted than the air outside EPA
- 1,000 ppm where rising COâ‚‚ starts to measurably dull focus and decisions Harvard COGfx
How it works
Watch outside. Read inside. Act.
Pick a situation and watch it ripple through: what we see outside, what your sensor reads inside, and how to take control of your environment.
01Outside
We watch the air around you.
02Inside
Your sensor reads what is in the room.
03Act
One clear thing to do.
The sensor
Six sensors. Twelve signals. One calm screen.
COâ‚‚, four particle sizes, VOCs and NOâ‚“, plus temperature, humidity, pressure and light, read by a Sensirion, Bosch and Texas Instruments sensor stack, and shown as one color you can read across the room.
- 6 sensors, 12 signals COâ‚‚, IAQ, PM1.0/2.5/4.0/10, VOC, NOâ‚“, temp, RH, pressure, light
- ±50 ppm + 2.5% Factory-calibrated CO₂ accuracy
- At a glance A screen up close, a colour-shift underglow across the room
- Outdoor-aware Fuses your live local weather and AQI
- Outdoor AQI 31
- Indoor air 27
- COâ‚‚ 727ppm
$249 USD
The system
More than just a sensor
You're not just buying hardware. The device is one piece. The web dashboard and the phone app turn it into a connected system that watches, remembers, and quietly nudges you when something shifts.
The web dashboard
The long view: hours, days, weeks of trend. AI surfaces the patterns you would never catch on the device itself, the rooms that drift, the hours that linger orange, the events that cluster.
The phone app
What your home noticed while you were out. Quiet, suggestive notifications, never commands. See your home from anywhere, and read the year-in-air letter each January.
The only monitor in its class to read all four particle sizes plus COâ‚‚, VOC and NOâ‚“ behind a touchscreen, then fuse them with your live outdoor air. See the full comparison.
Founder's Note
I'm Bear. A few years ago I got a little obsessed with the air inside my own home: the CO2 that climbs overnight, the VOCs off a new couch, the fine particles from cooking, the microplastics we're only beginning to understand. The more I learned, the more I wanted to see it - and actually do something about it.
So I set out to build the device I wished existed: one that measures what matters, blends it with the world outside, and tells you what to do, not just what to read. Open a window, change a filter, run the fan. Calmer decisions, not more worry.
Cleaner indoor air is one of the most underrated ways to feel a little better and tread a little lighter on the planet. Thanks for being here.
— Bear, Founder
- 1-year limited warranty
- 30-day returns
- Fast FedEx shipping
We publish the full competitor comparison, line by line. Read it yourself.
Ready when you are
Bring the outside air indoors, on your terms.
See exactly what your home is breathing, and the actionable insight to act on it, in real time.
$249 USD one-time
Buy Terrestream Explore the sensor- No subscription required
- 30-day returns
- 1-year limited warranty
Six sensors. Twelve signals.
Built on genuine Sensirion, Bosch, and Texas Instruments sensors.
- COâ‚‚
- IAQ
- VOC
- NOâ‚“
- PM1.0
- PM2.5
- PM4.0
- PM10
- Temperature
- Humidity
- Pressure
- Light
Included
- In the box: the sensor, USB-C cable, power adapter, and printed field guide
- Dashboard and mobile app included
- Privacy-first air data
Works with
- Home Assistant
- MQTT
Home Assistant
MQTT