AirGradient Open Air
airgradient · O-1PST
The AirGradient Open Air is an outdoor air quality monitor designed to measure environmental pollution and help you better understand the air quality around a home, school, community, or civic project. Its O-1PST model measures PM2.5, CO2, TVOC, NOx, temperature, and humidity, combining particle, gas, and environmental sensors in a weather-resistant enclosure. Unlike many closed commercial monitors, the AirGradient Open Air is fully open-source and open-hardware, allowing you to modify the firmware, inspect the schematics, adapt the device, or send data to your own platforms. It can be used with the AirGradient dashboard, displayed on the AirGradient map, shared with OpenAQ, or integrated directly with Home Assistant. The device uses an ESP32-C3-MINI microcontroller with 2.4 GHz WiFi and Bluetooth LE. Since Home Assistant 2024.6 and with updated firmware, AirGradient indicates native support with local autodiscovery, making it a very appealing option for users who want to track outdoor air quality within their home automation system. The Plantower PMS5003T particle sensor measures PM1, PM2.5, and PM10, although the manufacturer highlights PM2.5 as the most reliable reading. The SenseAir S8/S88 sensor measures CO2 using NDIR technology, which is useful for detecting local emission sources, although it is not intended to accurately measure small global atmospheric changes in CO2. It also includes a Sensirion SGP41 for relative TVOC and NOx indexes. The enclosure is made from UV-resistant ASA plastic suitable for outdoor conditions, with wall or pole mounting. The unit is powered via USB-C with a 4-meter cable and requires a 5V USB adapter rated above 2A, which is not included.
✓ Pros
- Open-source and open-hardware outdoor monitor
- Measures PM2.5, CO2, TVOC, NOx, temperature, and humidity
- Native Home Assistant support with local autodiscovery
- Compatible with the AirGradient dashboard and map
- Can share data with OpenAQ
- ASA enclosure resistant to UV rays and weather
- Wall or pole mounting
- 2.4 GHz WiFi and Bluetooth LE
- Customizable firmware
- Recognized sensors such as Plantower PMS5003T, SenseAir S8/S88, and Sensirion SGP41
- Available assembled or as a kit
✗ Cons
- USB power adapter not included
- Temperature and humidity may differ from actual ambient values
- CO2 is not intended to accurately measure global atmospheric changes
- TVOC and NOx are expressed as relative indexes
- No built-in battery
- No Ethernet or PoE
- The kit version does not include warranty or certifications
Compatibility
Specifications
| Model | O-1PST |
| Commercial name | AirGradient Open Air |
| Type | outdoor air quality monitor |
| Microcontroller | ESP32-C3-MINI |
| CPU | 32-bit single-core RISC-V up to 160 MHz |
| Memory | 384 KB ROM, 400 KB SRAM, 8 KB RTC SRAM, and 4 MB flash |
| Connectivity | 2.4 GHz WiFi IEEE 802.11 b/g/n and Bluetooth LE 5 with Bluetooth mesh |
| Measured sensors | PM2.5, CO2, TVOC, NOx, temperature, and humidity |
| Particle sensor | Plantower PMS5003T |
| Measured particles | PM1, PM2.5, and PM10 |
| PM2.5 accuracy | ±10% from 100 to 500 μg/m³ and ±10 μg/m³ from 0 to 100 μg/m³ |
| CO2 sensor | SenseAir S8/S88 NDIR |
| CO2 range | 0 to 10000 ppm |
| CO2 accuracy | ±40 ppm ±3% of reading between 400 and 2000 ppm |
| TVOC/NOx sensor | Sensirion SGP41 |
| TVOC accuracy | <±15 in VOC index 0 to 500 |
| NOx accuracy | <±50 in NOx index 0 to 500 |
| Temperature and humidity sensor | ENS210 integrated into the PMS5003T module |
| Temperature accuracy | ±0.2 °C |
| Humidity accuracy | ±3.5% RH |
| Extensions | I2C, 3 GPIO, and 2 UART exposed on PCB |
| Peripherals | status LED, button, USB-C connector, and Texas Instruments TPL5010 external watchdog |
| Enclosure | UV-resistant ASA plastic for outdoor conditions |
| Mounting | wall or pole |
| Included cable | 4-meter USB-C to USB-A cable with data lines for flashing |
| Required power supply | 5V USB-A adapter above 2A not included |
| Mounted version certifications | CE, RoHS, REACH, and FCC |
| Compatibility | native Home Assistant with updated firmware, Homey, AirGradient dashboard, AirGradient map, and OpenAQ |
| Power supply | USB-C 5V |
| Neutral wire required | No |
Related content
Watch on YouTube
Complete Guide: AirGradient O-1PST Outdoor Air Quality Sensor and Home Assistant
Ever wondered if the air you let into your home when you ventilate is actually healthy? In home automation we often focus on the indoors, but the AirGradient Open Air O-1PST changes the game. This professional-grade open-source sensor integrates seamlessly with Home Assistant, letting you make smart decisions based on real environmental data.
Read review