Adafruit ENS161 MOX Gas Sensor - STEMMA QT / Qwiic

The ENS161 is a broad-spectrum Metal Oxide (MOX) sensor primarily sensitive to Volatile Organic Compounds (VOCs) such as ethanol, hydrogen, and toluene. It does not output specific gas concentrations but provides algorithmically derived indices: equivalent CO2 (eCO2), equivalent Total VOC (eTVOC), and two Air Quality Index (AQI) values, which correlate to overall indoor air quality.

Yes. The breakout module includes onboard voltage regulation and logic level shifting, making it fully compatible with both 3.3V and 5V systems. You can safely connect its I2C lines (SDA, SCL) and power it from a 5V pin on an Arduino Uno or Mega without risk of damage to the sensor IC.

The STEMMA QT connector is a 4-pin JST SH plug. Use a matching STEMMA QT cable (sold separately) to connect the module's output port directly to another STEMMA QT/Qwiic compatible board (like an Adafruit microcontroller). This provides power, ground, SDA, and SCL in a single, solder-free cable, enabling quick prototyping and daisy-chaining.

The ENS161 IC features built-in algorithms and automatic baseline correction. Upon first power-up, it performs an initial conditioning cycle (up to 15 minutes) to stabilize. For optimal accuracy in varying environments, the sensor supports optional compensation by providing external temperature and humidity data via its I2C interface.

AQI-U (Universal Air Quality Index) is a standardized index for general indoor air quality assessment. AQI-S (Sensitive Air Quality Index) is tailored for environments where sensitive individuals are present, using a different weighting of the sensor inputs. Both provide a 1-5 scale rating, with 1 being excellent and 5 indicating poor air quality.