MQ-series gas (MQ-2/135…)
Also known as: MQ-2 · MQ-135 · MQ-7 · MQ gas sensor · More staples
In every starter kit, so everyone tries one — and then discovers why serious builds don't use them. Listed here so the comparison is honest.
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Avoid for new builds — see the gotchas for what to buy instead.
At a glance
⚑ flag an error| Measures | gas |
|---|---|
| Accuracy | Uncalibrated analog gas response — qualitative at best |
| Interface | analog (plus a 150–200 mA heater) |
| Supply | 5 V, heater 150–200 mA |
| Battery-viable | No (continuous draw) |
| ESPHome | Generic ESPHome component (adc/gpio) — adc |
| Typical price | $1-2 (street, varies) |
Compare all sensor modules in one table →
Which one do I buy?
vs SGP41/ENS160: the modern MOX sensors are calibrated, compensated, I2C and don't need a heater budget. There is no use case left where the MQ wins except price.
Clone check
Good for
Gotchas to know
- The heater's 150–200 mA browns out ESP boards sharing a weak 5 V supply — the classic mystery reboot.
- Needs 24–48 h burn-in and per-gas calibration that effectively nobody does; readings are relative hand-waving.
- For VOC buy an SGP41/ENS160; for CO safety buy a certified CO alarm, never a $1 module.
Wiring it up
Analog output: use an ADC1 pin (ADC2 fights with Wi-Fi), expect the ESP32's ADC to be nonlinear at the extremes, and calibrate in software. Any dev board with a spare ADC pin works.