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All issues

Wi-Fi will not connect

How are you connecting?

App or web dashboard

Continue in Add device in the app or dashboard. This path pairs over Bluetooth.

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What to look for

Setup finishes and the sensor appears in the account you used. Use that same account in the app and dashboard.

Mobile app setup Computer setup

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Device browser setup

Choose this path for the sensor’s Set up with a browser option. It connects Wi-Fi without linking an online account.

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What to look for

The sensor connects to Wi-Fi and can synchronize its clock when internet access is available. Use Add device in the app or dashboard for account access.

Local browser setup Add the sensor to an account

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All issues

Pairing or account linking fails

How are you connecting?

Mobile app

The app uses the current six-digit Bluetooth code shown on the sensor’s Pairing screen.

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What to look for

Finish Wi-Fi setup and check that the sensor appears in this account. If it is already linked elsewhere, use the owning account or the transfer guide.

App setup steps Ownership transfer

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Computer

Use Chrome or Edge on a computer with Bluetooth. The sensor’s Set up with the app button also starts computer pairing.

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What to look for

Finish Wi-Fi and account setup in the dashboard. The sensor should appear under the account used for setup.

Computer setup steps Open web dashboard

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Home Assistant

Home Assistant uses its own eight-digit code, including leading zeros. This code expires after two minutes.

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What to look for

Open the device in Home Assistant and check that its readings appear. Allow warm-up or cleaning to finish if needed.

Home Assistant pairing guide Install Terrestream Local

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All issues

Readings look unusual

Check the readings

Keep the sensor powered in open room air. After setup, particles settle in about 30 seconds, VOC Index in about 1 hour and NOx Index in about 6 hours. CO₂ reaches its stated accuracy after about 2 days that include fresh air.

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What to look for

Readings continue updating. If unusual readings persist after these checks, contact support with the screenshot and placement details.

Sensor placement CO₂ self-calibration Measurement evidence

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All issues

Screen, touch or update is stuck

Check the device

Keep the sensor powered while an update is visible. Wait for that state to finish before trying a restart.

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What to look for

The normal reading screen or setup flow resumes. If it remains frozen, contact support and describe what the screen shows.

Power and first setup

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All issues

Fan sound or cleaning animation

Check the sound

The scheduled SEN66 self-clean runs on the first Tuesday of each month, around 10 AM local time, and lasts about 13 seconds. A cleaning animation may appear.

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What to look for

A brief sound that stops with readings updating is expected. Contact support if the sound is constant, repeats often or comes with frozen readings.

Fan cleaning schedule Quiet Hours settings

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All issues

Reset or transfer ownership

Prepare for reset

Factory reset clears saved Wi-Fi, settings, claim and account-linking information from the device. Be ready to set it up again.

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What to look for

The sensor returns to first setup. If you cannot access settings or no longer have it, contact support from your account email with the device details you have.

Reset and ownership guide Set up again Personal data requests

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More answers
New owner basics
Power and box contents
Terrestream is plug-in only. It runs on continuous USB-C power and has no battery, so it stops measuring if it loses power. The box includes a 6 ft (1.8 m) USB-C cable, a power adapter and a printed guide.

Read the guide

Wi-Fi requirements
Terrestream connects to 2.4 GHz Wi-Fi only; a 5 GHz-only network won't work. Wi-Fi is optional: without it, readings still show on the device's screen. Connected features need 2.4 GHz Wi-Fi, internet and a free account.

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The first days
Leave Terrestream powered on. Particle readings settle within about 30 seconds of starting. The VOC index meets its specification after about 1 hour and the NOx index after about 6 hours. CO2 readings reach their stated accuracy after about 2 days of operation that include fresh air, and they need fresh air (around 400 ppm, for example after airing out the room) at least once a week to stay accurate.

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Screen colors, leaves and stars

Every reading uses the same six colors, each with its own thresholds: green is Good, yellow is Moderate, orange is Unhealthy for sensitive groups (shown as “Unhealthy*”), red is Unhealthy, purple is Very Unhealthy and maroon is Hazardous.

Leaves (Carbon Dioxide screen): 5 filled leaves up to 600 ppm, 4 up to 1,000 ppm, 3 up to 1,500 ppm, 2 up to 2,000 ppm, 1 up to 2,500 ppm and none above 2,500 ppm.

Stars (Indoor Air Quality screen): 5 stars for an IAQ of 0–50, 4 for 51–100, 3 for 101–150, 2 for 151–200, 1 for 201–300 and none above 300.

AQHI+ (the default when the device language is French): the screen shows Air Quality Health with Low Risk (green, 1–3), Moderate Risk (yellow, 4–6), High Risk (orange, 7–10) or Very High Risk (red, above 10), and 5 stars for 1–2, 4 for 3, 3 for 4–6, 2 for 7–8, 1 for 9–10 and none above 10.

Without internet
The sensor keeps measuring and shows readings on its own screen without Wi-Fi, internet or an account. App notifications, history, outdoor context and recommendations need 2.4 GHz Wi-Fi, internet and a free account. If our cloud service is unreachable, the screen keeps working, and app notifications and history resume when the sensor reconnects.

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Size and weight
Terrestream measures 69 × 65 × 111 mm (2.72 × 2.56 × 4.37 in) and weighs 6.7 oz (190 g).
Setup & pairing
Set up Terrestream
Connect the supplied USB-C cable and power adapter. Choose your language and accept the terms on the device. Follow the getting-started guide for mobile app, web dashboard, or standalone use. An account is needed for app and dashboard access, but not for standalone readings.

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Device behavior
Quiet hours
Use Quiet Hours to set a start and end time for calmer overnight behavior. Brightness, LED level, and volume are also adjustable from the device and app.

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Use touchscreen
Use the menu control on the screen for About, Setup, Settings, Update, Privacy, and regulatory information. Tapping the reading area moves between the main air-quality views.
Firmware updates
Terrestream checks weekly for signed firmware updates during an overnight maintenance window. You can also start a manual update from device settings when one is available.
App & dashboard
App and dashboard
The Terrestream app and dashboard are designed for live readings, history, notifications, and device settings. The dashboard is the deeper view for reviewing room behavior over time.

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History and export
Use the app or dashboard to review recent history. To request a copy or a portable export of your personal data, use the privacy self-service portal.

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Accuracy & sensors
Measured signals
Terrestream measures particulate matter, CO2, VOC index, NOx index, temperature, humidity, pressure, and light so the app can explain what changed and why it may matter.

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CO₂ recalibration
The CO2 sensor calibrates itself automatically, so there is no manual recalibration to run. Self-calibration needs the sensor to get fresh outdoor-level air (around 400 ppm) at least once a week. Open the windows in the room where your Terrestream sits, or ventilate it well, until the CO2 reading stops falling and settles near the outdoor level. Do this at least once a week, and keep the sensor powered on. A room that is never aired, such as a tightly sealed room or a bedroom that stays shut, falls outside these conditions, and its readings can drift. After a thorough airing, the reading should come close to 400 ppm; if it stays well above that week after week, contact support. The sensor's stated CO2 accuracy is ±(50 ppm + 2.5% of reading) from 400 to 1,000 ppm, ±(50 ppm + 3%) from 1,001 to 2,000 ppm and ±(40 ppm + 5%) from 2,001 to 5,000 ppm. It applies after 2 days of operation that include fresh air, with self-calibration on and fresh air at least once a week. Sensirion adds a typical drift of ±(5 ppm + 0.5%) per year, starting after five years.

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Integrations
Is Terrestream compatible with Alexa?

Yes. Compatible with Alexa through the Terrestream skill. Enable the skill in the Alexa app, sign in to Terrestream and choose the sensors to share. Ask for supported readings and create routines. Requires cloud sync, internet and a verified Terrestream account that owns the sensor. Available in the United States with Alexa set to English (US). No Terrestream subscription is required. Open the Terrestream skill.

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What can I ask Alexa?

After linking the Terrestream skill, try “Alexa, what is the carbon dioxide level of Main bedroom?” or “Alexa, what is the temperature of Main bedroom?” Replace Main bedroom with your monitor’s Alexa name. Use the Terrestream app or web dashboard for full measurement history. Custom spoken window advice is not included; check window guidance on the Alexa device page or create a recommendation routine.

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Use Terrestream in an Alexa routine

In Alexa, open More → Routines → + → Add an event → Smart Home and choose your Terrestream monitor. For a window reminder, select Terrestream announcements → Opening windows may help, add a spoken action and choose your Echo. Save the routine. For an immediate check, use the Connection test recipe in your Alexa manager. Recommendations need a saved home location and outdoor-data permission. Alexa runs the actions you configure.

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Home Assistant / MQTT

Install the Terrestream Local integration through HACS to read all 12 measurements locally in Home Assistant. MQTT workflows are also supported. Alexa connects separately through the Terrestream skill; no Home Assistant or Matterbridge setup is needed for that connection.

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Do I need Matter for Alexa?

No. The Terrestream skill connects Alexa to the sensors you authorize through your Terrestream account. You do not need a Matter bridge, Home Assistant or a Matter QR code. The sensor itself is not a native Matter device.

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Privacy & security
Data sent
Terrestream is built around privacy-first air data. For access, correction, export, deletion, or jurisdiction-specific requests, use the privacy self-service portal.

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Delete or export data
Yes. Submit an access, deletion, correction, or portability request through the privacy self-service portal and we will process it through the verified privacy workflow.

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Data resale
We don't sell your personal information. With your opt-in, our website shares browsing and purchase events with advertising partners (Pinterest, Meta, Reddit) to measure ads. The app doesn't track you. For binding details about personal information, service providers, sharing, and privacy rights, see the Privacy Policy and use the privacy self-service portal.

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Orders & returns
Returns / warranty / RMA
Return it within 30 days of delivery, even if you've opened and used it. You pay return shipping. Your first return has no restocking fee. For a defective device, the 1-year limited warranty applies. See the returns policy for the details, then contact support with your order number to start a return or RMA.

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Shipping status
Use the order status page to look up shipment and order information. If something looks wrong, contact support with your order ID.

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When it ships
Ships the next business day via FedEx. To check on an order, use the order status page.

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Compare
Do I need a subscription?
No. The apps, web dashboard and account are free, and core recommendations are included.

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Compare monitors
Use the comparison overview for a fair, cited summary of the main indoor-air monitors. The comparison is factual: sensor stack, local-friendly workflows, dashboard interpretation, radon support, portability, display, and app ecosystem vary by model.

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WhatsApp support