Sensirion SCD41
Also known as: SCD41 · SCD4x · Air quality
The 2026 default CO2 sensor: real NDIR measurement (not a VOC guess) in a tiny package, native ESPHome support, and a single-shot low-power mode that makes battery CO2 nodes actually possible.
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At a glance
⚑ flag an error| Measures | co2, temperature, humidity |
|---|---|
| Accuracy | TRUE CO2 (photoacoustic NDIR), 400–5000 ppm ±(40 ppm + 5 %) |
| Interface | I2C @ 0x62 |
| Supply | 2.4–5.5 V |
| Battery-viable | Yes (deep-sleep friendly) |
| ESPHome | Native ESPHome component — scd4x |
| Typical price | $9-16 (street, varies) |
Compare all sensor modules in one table →
Which one do I buy?
SCD40 vs SCD41: same family — the 41 measures to 5000 ppm (vs 2000) and adds the single-shot low-power mode. Pay the couple of dollars for the 41 unless the 40 is much cheaper that day.
Clone check
Good for
Gotchas to know
- Understand automatic self-calibration (ASC): it assumes the sensor sees fresh air (~400 ppm) weekly. In a never-empty home, disable ASC and force-calibrate outdoors occasionally.
- Self-heats — the onboard temperature runs warm; use the offset config if you use its T/RH.
- Needs a stable 3.3/5 V supply; brownouts produce garbage readings.
Wiring it up
It's I2C, so it shares two pins with every other I2C sensor you own — chain your climate/light/CO2 stack on one bus and mind the address clashes (this one lives at 0x62). Any ESP32 dev board works.