What is IAQ?
A single composite score that summarizes indoor air, calibrated to the same 0–500 scale as the U.S. EPA outdoor AQI.
Articles tagged "On the device"
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Carbon dioxide indoors
Every exhale adds COâ‚‚ to the room. Past about 1,000 ppm, focus slips. Past 1,500, headaches.
PM2.5: the fine stuff
Particles smaller than 2.5 micrometers slip past your nose, lodge deep in the lungs, and cross into the bloodstream. They are the single most-studied air pollutant.
PM10: dust, pollen, and the coarse fraction
Larger particles that mostly get filtered in the upper airway, but they still matter for allergies, asthma, and visibility.
VOCs: the invisible smell
Volatile organic compounds are the carbon-based gases evaporating off everything: cooking, candles, paint, new furniture. Some are merely annoying. Some are not.
NOâ‚“: gas stoves, traffic, asthma
Nitrogen oxides come from combustion. Indoors, the main source is a gas stove. The health link with childhood asthma is robust.
Humidity: the 30 to 50 percent rule
Below 30%, your throat dries out and viruses last longer. Above 60%, mold and dust mites thrive.
Temperature: comfort, sleep, productivity
ASHRAE defines a comfort zone. The bedroom is its own special case: cooler is better.
Barometric pressure: weather, altitude, headaches
Pressure rarely changes how the air feels, but it changes how the body feels. It is also the most reliable indoor weather forecast you have.
Lux: light, circadian rhythm, and screen time
Light is information your body uses to set its clock. Most indoor environments give it the wrong information.
How the sensor sees: optical COâ‚‚ vs MOX
COâ‚‚ is read by pulsing infrared light the gas absorbs and listening for the pressure wave. VOCs are read by watching a hot ceramic surface change conductance. Different physics, different limits.
Cross-sensitivities: what confuses each sensor
Every sensor has things it sees that it shouldn't. Knowing the cross-sensitivities is how the dashboard tells you the right story.
Where to put the sensor
Counter-height, away from vents and windows, in the room you actually use. The placement choice changes what you can interpret.
Open vs. closed windows
The single most consequential daily decision the dashboard helps you make. Six outdoor signals, three indoor signals, one answer.
How long until the air clears
CADR, room volume, air changes per hour. The math behind "the room should clear in about 20 minutes."
Reading the dashboard
What "elevated," "spike," "trend," "baseline," and "anomaly" mean. The vocabulary the AI uses.
A renter's guide to indoor air
You can't replace the HVAC, but you can do most of what matters. Eight interventions that need no landlord permission.
What the AI can and cannot tell you
The dashboard interprets your air. It does not diagnose you, replace your doctor, or detect things the sensor cannot measure.
Dashboard vocabulary
The small set of words the dashboard uses with specific, defined meanings. Precision in the vocabulary lets the AI and the reader stay aligned.
How anomaly detection works
When the data does not match any known pattern, the dashboard logs the event and asks for help interpreting it. That is by design.
Multi-room comparison
Two sensors tell more than one twice. The difference between rooms is often where the real story is.
Circadian and ambient context
Why the dashboard shows sunrise, sunset, and moon phase alongside the air-quality data. Time of day is a meaningful signal.
Returning home: vacation recovery
A sealed empty home behaves predictably while you are gone. The first 24 hours back tells you what changed.
Where do the numbers come from?
Every reading on the dashboard has a source: a sensor on the device, a computation from sensor inputs, or an outdoor API. Knowing which is which is the first step in interpreting any of them.
Sensor drift over time: what to expect after year one
The SEN66's individual channels each drift differently. COâ‚‚ self-calibrates against outdoor air, PM loses a few percent per year, VOC and NOâ‚“ are relative baselines by design. Here is what changes and what does not.
When the data itself is unreliable
Sensors fail in a small set of recognizable ways. The dashboard flags the failures and the AI refuses to act on them. Here is how to tell a real spike from a glitch.
How the Terrestream sensors actually work
Three sensor packages, six sensing elements, twelve signals. Here is what is inside the device, what each part measures, and the physical reasons it can and cannot do what it does.
How air-quality sensors work
The Terrestream stack combines direct measurements, index outputs, context sensors, and interpretation. Those are different evidence classes, and the distinction matters.
Lux and indoor-air context
Lux helps interpret placement, daylight, display behavior, and occupancy patterns. It is not proof of circadian lighting performance or WELL lighting compliance.
Set up your Terrestream
A short first-run path: power the sensor, pair it, connect Wi-Fi, claim it to your account, then place it where the room air can circulate.
Pair with the app
Use the 6-digit passkey on the device screen to create an encrypted Bluetooth pairing, then finish the claim flow in the app.
Connect to Wi-Fi
Terrestream uses 2.4 GHz Wi-Fi. You can configure it from the app or use the temporary setup network when no Wi-Fi is saved.
The Tuesday-morning fan sound
A brief Tuesday fan sound is normally the SEN66 sensor self-clean cycle.
Quiet hours, brightness, and sound
Use Quiet Hours and device/app settings to reduce display, light, and sound behavior on a schedule.
Factory reset your device
Factory reset clears saved device configuration, claim, and account-linking information so the sensor can be paired again.
Before you sell or give away your device
Factory reset the sensor before another person receives it.
Compare indoor air-quality monitors
A fair, sourced buyer guide to Terrestream, AirGradient ONE, Ruuvi Air, Awair Element, Airthings View Plus, Aranet4 HOME, Kaiterra Sensedge Mini, and IQAir AirVisual Pro.
Terrestream vs Awair Element
Awair Element is a compact five-factor monitor; Terrestream adds broader particulate sizing, NOx, pressure, light, and deeper interpretation.
Terrestream vs Airthings View Plus
Airthings View Plus is compelling when radon is central; Terrestream emphasizes multi-signal indoor behavior and local-friendly workflows.
Terrestream vs Aranet4 HOME
Aranet4 HOME is a focused portable CO2 monitor; Terrestream is a broader room air-quality system.
Terrestream vs IQAir AirVisual Pro
IQAir AirVisual Pro emphasizes PM2.5, CO2, AQI, and a large color display; Terrestream adds more indoor channels and source interpretation.
Terrestream vs AirGradient ONE
AirGradient ONE is an open-home indoor monitor with strong local-home appeal; Terrestream emphasizes polished room interpretation, commercial evidence, and buyer-ready guidance.
Terrestream vs Ruuvi Air
Ruuvi Air is a credible open-friendly SEN66 monitor; Terrestream emphasizes Wi-Fi-direct operation, a touchscreen display, outdoor-data fusion, and US buyer readiness.
Terrestream vs PurpleAir
PurpleAir is strongest as a particle and outdoor-map ecosystem; Terrestream is built for indoor room decisions across particles, gases, comfort, context, and recommendations.
Terrestream vs Apollo AIR-1
Apollo AIR-1 is a compact ESPHome/Home Assistant monitor with strong local-control appeal; Terrestream emphasizes a finished room device, broader buyer guidance, and included cloud intelligence.
Breathe Better. Live Smarter.
Turn air-quality knowledge into action.
One sensor. Twelve signals. Indoor readings connected to outdoor context and plain-English recommendations. Everything you just read can be measured live in your own home.
$249 USD one-time
Buy Terrestream Explore the sensor- No subscription required
- 30-day returns
- 1-year limited warranty
- Fast shipping via FedEx
Six sensors. Twelve signals.
Built on genuine Sensirion, Bosch, and Texas Instruments sensors.
- COâ‚‚
- IAQ
- VOC
- NOâ‚“
- PM1
- PM2.5
- PM4
- 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