Gas sensor: warm-up, calibration and alarm level

The gas sensor heats a small element and measures how its resistance changes when gas or smoke is in the air. It gives an approximate number (ppm) — good for “more” or “less”, not a laboratory measurement.

Warm-up

For the first 90 seconds after power-on no value is shown. A new sensor can also behave oddly for the first day while it settles.

Calibrate in clean air

After the sensor has been on for a few minutes, in fresh air, give the BOOT button on the board one short press. The sensor then takes the present air as “clean”.

Alarm level

The default alarm level is 300 ppm. Change it by editing the gas sensor in More → Rooms. Lower = earlier warning but more false alarms.

Careful: The gas sensor is not a certified gas or smoke detector. Do not rely on it for your safety.