AirCube

See your air. AirCube is a desktop air quality monitor with built-in Home Assistant support over Zigbee or Bluetooth (BLE). Every model tracks temperature, humidity, eCO2, eTVOC, and VOC Level; AirCube Pro also measures true CO2 and ambient light. A glanceable LED shows the current air quality.

Works standalone out of the box. Pairs with Home Assistant in minutes. Other platforms are supported through community-contributed extensions.

AirCube Web -- Live readings, history and firmware updates in your browser. Nothing to install.

Watch the overview -- What AirCube does and why it's open source, in under three minutes.

StuckAtPrototype Labs -- Step-by-step video walkthroughs: ZHA setup, Zigbee2MQTT setup, and updating firmware from the browser.

AirCube -- Assembled AirCube

AirCube Populated PCB -- AirCube Populated PCB

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Getting Started

1. Plug it in -- Connect the USB-C cable to any USB port or charger. AirCube powers on automatically.

2. Wait for warm-up -- The air quality sensor needs about 3 minutes to stabilize after power-on. During this time, the LED may not reflect accurate readings.

3. Read the color -- Once warmed up, the LED tells you everything:

The color shifts smoothly as conditions change. No app needed -- just glance at it.

Firmware 1.5.0 and above drive the LED from canonical VOC Level (TVOC-derived, absolute). The color is a smooth green-to-red gradient -- same feel as older firmware, but tied to fixed indoor-air bands instead of the relative AQI-S baseline. See LED Reference for the exact mapping. Firmware 1.4.3 and below used the same gradient shape, but driven by AQI-S instead.

4. Adjust brightness -- Press the button to cycle through brightness levels.

That's it. AirCube works out of the box with no setup, no accounts, and no Wi-Fi.

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Base vs. Pro

Both models use the ScioSense ENS161 for VOC Level, eCO2, and eTVOC. Choose Pro when you also want a direct CO2 measurement and automatic LED dimming based on room light.

eCO2 vs. true CO2: eCO2 is an estimate derived from detected VOCs. The Pro's SCD41 measures CO2 directly using NDIR, while the ENS161 still detects odors and fumes that a pure CO2 sensor can miss.

What AirCube Measures

Understanding the readings

AirCube Base uses a ScioSense ENS161 gas sensor and an ENS210 temperature/humidity sensor. AirCube Pro uses the ENS161 alongside an SCD41 for true CO2, temperature, and humidity, plus a VCNL4040 ambient light sensor.

eCO2 (ppm) -- Estimated CO2 derived from detected VOCs, not a direct CO2 measurement. Useful for judging ventilation; also picks up odors and fumes a pure CO2 sensor would miss.

eTVOC (ppb) -- Total volatile organic compounds in the air. Spikes after cooking or cleaning are normal; sustained high readings mean you should ventilate.

VOC Level (0--500) -- TVOC mapped to a fixed indoor-air scale (firmware 1.5.1+). Linear ramp between band edges; TVOC-only (eCO2 does not affect VOC Level). Reported over Zigbee and USB serial.

On Base hardware, the LED color is derived from TVOC/VOC Level alone (eCO2 does not drive the LED). VOC Level is linear between band edges, so the LED fades smoothly. See below for Pro's CO2 arbitration.

AQI-S (deprecated, USB serial only) -- A legacy ScioSense relative score from firmware before 1.5.0. As of firmware 1.5.0, AQI-S is deprecated and always reports 0 -- it's kept in the serial output only for compatibility with older tools. Use VOC Level, eCO2/eTVOC, or true CO2 (Pro) instead.

VOC Level drives the LED color on Base hardware. On Pro, the LED shows whichever is worse -- VOC Level or CO2 Level (from the true CO2 reading). See LED Reference.

Warm-up and initial start-up

The ENS161 needs about 3 minutes of warm-up in standard mode before readings stabilize. On the very first power-on of a new sensor the initial start-up takes about 1 hour as the sensor conditions itself. Readings during these periods may be inaccurate -- the LED and status flag will indicate when the sensor is ready.

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Built-in vs. community

Maintained by StuckAtPrototype: firmware, hardware, desktop app, and the Home Assistant integration documented in HOME_ASSISTANT.md.

Community-contributed: integrations built and shared by the community. They live in this repo and are welcome, but StuckAtPrototype does not test or ship them. They may require extra setup and can break when a vendor updates their platform. See Community extensions.

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Home Assistant Integration

AirCube was designed for Home Assistant. It connects over Zigbee -- no USB cable to your server, no cloud, no Wi-Fi credentials to configure. Plug it in, hold the button for 3 seconds to start pairing, and six core entities show up: temperature, humidity, eCO2, eTVOC, VOC Level, and brightness.

AirCube Pro adds two more: true CO2 (SCD41) and illuminance (VCNL4040). Both are exposed in ZHA and Zigbee2MQTT 2.x -- eight entities total on a Pro.

Once connected you can:

• Track air quality over time with built-in history graphs
• Set up automations -- turn on a fan when eCO2 gets too high, send a notification when VOC Level spikes
• Monitor every room -- each AirCube pairs independently, name them however you like

You'll need: a Zigbee coordinator dongle (we recommend the SONOFF ZBDongle-E, ~$13) plugged into your Home Assistant machine.

Works with ZHA (built-in) and Zigbee2MQTT.

Video walkthroughs: Set up AirCube with ZHA · Set up AirCube with Zigbee2MQTT

Full setup guide: Connecting AirCube to Home Assistant

No Zigbee dongle? AirCube also works over Bluetooth

AirCube boots into BLE mode by default (until you pair it to Zigbee) and broadcasts standard BTHome data -- temperature, humidity, CO2, and TVOC. If your Home Assistant instance has a Bluetooth adapter or an ESPHome Bluetooth proxy nearby, it can often pick up these readings passively, with no pairing step and no Zigbee hardware at all. Building a custom BLE client? See the BLE GATT Protocol reference.

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Community extensions

The integrations below are community-contributed. They are not maintained by StuckAtPrototype and compatibility with vendor hub or app updates is not guaranteed.

SmartThings (Samsung Zigbee hub) — community-contributed

Some users run AirCube on a Samsung SmartThings Zigbee hub over Zigbee (no Wi-Fi configuration on the device). The hub must support SmartThings Edge.

By default, the SmartThings app may only show temperature and humidity until you install the community AirCube Zigbee Edge driver from this repository and assign it to the device.

Full setup guide: Connecting AirCube to SmartThings (pairing, SmartThings CLI, driver channel, verification in the app and Advanced Web App).

Troubleshooting: If you only see temperature and humidity, install the AirCube Zigbee Edge driver from smartthings/aircube-zigbee/ and assign it to the device. Details are in SMARTTHINGS.md.

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Connect to Your Computer

Plug the AirCube into your computer with a data-capable USB-C cable to see live readings, charts, and history.

In your browser -- nothing to install

AirCube Web connects over USB straight from Chrome or Edge: live readings, LED brightness, history with CSV export, and firmware updates. Click Connect, pick your cube, and you're in.

Download the app

Check the Releases page for a ready-to-run Windows .exe -- no install required.

Or run from source

git clone https://github.com/StuckAtPrototype/AirCube.git
cd AirCube/scripts
pip install -r requirements.txt
python aircube_app.py

Select your serial port, click Connect, and you'll see live data.

Tip: Prefer a minimal taskbar-only view? See the companion AirCube Tray repo -- a lightweight Windows system-tray app that shows VOC Level as a live, color-coded number in your taskbar. It ships its own installer.

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Firmware Updates

The current firmware is v2.0.7. It keeps the cube responsive when plugged into a charger or closed port, and on Pro units it disables SCD41 automatic self-calibration (replaced by a 425 ppm fresh-air calibration) and detects a CO2 channel that has stopped reporting. See the v2.0.7 release notes.

Flash it now with AirCube Web or read the Firmware Update Guide for step-by-step instructions.

Video walkthrough: Updating the AirCube is easy (web UI) -- under two minutes, start to finish.

All releases: GitHub Releases

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Assembling Your AirCube

Building one yourself from printed parts and a populated PCB? All you need is three M2 x 5 mm screws and a small Phillips screwdriver -- about ten minutes of work.

Assembly Guide -- photo walkthrough for both Base and Pro.

Printable enclosure files live in mechanical/base/ and mechanical/pro/.

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LED Reference

Firmware 1.5.0 and above

The LED is a continuous green-to-red gradient driven by canonical VOC Level (TVOC-derived). The hue moves linearly with VOC Level: pure green up to VOC Level 10, then fading green → lime → yellow → orange → red, reaching full red at VOC Level 200. eCO2 does not affect the LED.

flowchart LR
    A["VOC Level 0–10<br/>TVOC 0–~43 ppb"] --> G["Steady green"]
    B["VOC Level 10–200<br/>TVOC ~43–2 200 ppb"] --> GR["Green → lime → yellow → orange → red"]
    C["VOC Level 200+<br/>TVOC 2 200+ ppb"] --> R["Steady red"]

Key gradient landmarks: yellow around VOC Level 105 (~730 ppb) and orange around VOC Level 150 (~1,460 ppb). Over Zigbee, TVOC-derived VOC Level is reported alongside eCO2, eTVOC, temperature, humidity, and brightness. AQI-S is deprecated, always reports 0, and does not drive the LED.

On Pro hardware, the LED shows whichever reading is worse: VOC Level (as above) or CO2 Level, a 0--500 score derived from the true SCD41 CO2 reading using the same band scale. If CO2 Level is higher than VOC Level, the LED reflects the CO2 reading instead. On Base hardware, CO2 Level is always 0, so VOC Level always drives the LED.

Firmware 1.4.3 and below (legacy)

Same gradient shape as above, but driven by AQI-S (relative, 24-hour baseline) instead of canonical VOC Level:

Button

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Troubleshooting

LED doesn't turn on

• Make sure the USB-C cable is firmly connected and the power source is active.
• Try a different USB port or charger.

Readings seem wrong right after power-on

• Normal. The air quality sensor needs about 3 minutes to warm up. Readings will stabilize.

Computer doesn't detect AirCube

• Some USB cables are charge-only. Use a cable that supports data.
• Windows users may need to install USB drivers.
• Linux users: add yourself to the dialout group and re-login.

Home Assistant: eCO2, TVOC, or VOC Level sensors are missing

• The custom quirk or converter isn't loaded yet. See the Home Assistant guide for step-by-step instructions.

Home Assistant: CO2 or Illuminance is missing (Pro)

• These come from standard Zigbee clusters, so ZHA and Zigbee2MQTT 2.x pick them up without any extra configuration. If they're absent, confirm the unit is a Pro (Base has no SCD41 or VCNL4040), then remove and re-pair so the coordinator re-reads the endpoint. The legacy Zigbee2MQTT 1.x converter does not expose them.

Home Assistant: AirCube won't pair

• Make sure permit join is enabled in ZHA or Zigbee2MQTT.
• Hold the button for 3 seconds to enter pairing mode (LED flashes blue).
• Move AirCube closer to the coordinator during pairing.

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Open Source

AirCube is fully open source -- firmware, PCB design, enclosure, desktop software, and Home Assistant integration. Community-contributed integrations (see Community extensions) also live in this repository. Everything is under the Apache 2.0 license.

Developers and makers: See the Contributing Guide for build instructions, architecture docs, serial protocol reference, and how to submit changes. Curious about the PCB? These Holes Are Why My Circuit Board Works explains the cutouts in the board.