Adafruit SCD-41 - True CO2 Temperature and Humidity Sensor

MQ-2 Gas Sensor

Combustible gas and smoke sensor: LPG, propane, methane, alcohol, hydrogen and smoke response. Analog output plus a digital threshold pin. Needs heater preheat.

MQ-3 Gas Sensor

Alcohol-biased MOX sensor for ethanol vapour and breath-alcohol style prototypes. Analog output plus a digital threshold pin. Needs heater preheat.

MQ-135 Gas Sensor

Broad indoor-pollutant MQ sensor biased to NH3, NOx, benzene, smoke and CO2-style response. Analog output plus a digital threshold pin. Needs heater preheat.

Grove - Air quality sensor

Grove indoor-air-quality sensor for a broad mix of CO, alcohol, acetone, thinner and formaldehyde. Single analog index, not a calibrated ppm reading.

Particulate Matter Sensor - SPS30

Sensirion SPS30 optical particulate sensor. Use for PM monitoring, not as a VOC/eCO2 or combustible-gas substitute.

Particle, VOC, Humidity, and Temperature Sensor - SEN54

Sensirion SEN54 combined module: particulate matter plus VOC, humidity and temperature. Useful upgrade path from PM-only designs, but firmware and airflow change.

SparkFun Air Quality Sensor - SGP40 (Qwiic)

Sensirion SGP40 Qwiic VOC-index sensor. Good for IAQ trends over I2C, not a gas-specific ppm sensor and not true CO2.

SparkFun Indoor Air Quality Sensor - ENS160 (Qwiic)

ENS160 Qwiic indoor-air-quality sensor with AQI, TVOC and eCO2-style outputs. Not a true CO2 sensor and not an MQ drop-in.

Fermion: ENS160 Smart Air Quality Sensor - TVOC/eCO2/AQI Monitor (Breakout)

ENS160 breakout with TVOC, eCO2 and AQI outputs over I2C/SPI. Similar sensing class to ENS160 Qwiic boards, but connector and board format differ.

Fermion: BME688 AI Environmental Sensor (VOC, Temperature, Humidity, Pressure)

BME688 multi-environment sensor: VOC plus temperature, humidity and pressure. Does not replace particulate or direct CO2 measurement.

Fermion: SGP40 VOC Air Quality Sensor - Smart IAQ Monitoring (Breakout)

SGP40 VOC sensor breakout for indoor-air trend monitoring. Same broad VOC-index branch as SparkFun SGP40, but board format and connector differ.

Fermion: BMV080 - World's Smallest Fanless Air Quality Sensor (PM1, PM2.5, and PM10)

Bosch BMV080 fanless particulate module for PM1, PM2.5 and PM10. Not a VOC/eCO2 or combustible-gas substitute.

Adafruit MiCS5524 CO, Alcohol and VOC Gas Sensor Breakout

MiCS-5524 gas sensor breakout for CO, alcohol, VOC/natural-gas leakage style prototypes. Analog MOX-style signal, not a calibrated safety instrument.

Adafruit SGP30 Air Quality Sensor Breakout - VOC and eCO2

SGP30 I2C MOX gas sensor with TVOC and eCO2 outputs. eCO2 is estimated from gas response, so use SCD/STCC modules when direct CO2 matters.

Adafruit SCD-30 - NDIR True CO2 Temperature and Humidity Sensor

SCD-30 NDIR true-CO2 module with temperature and humidity. Bigger and pricier than SCD-40/SCD-41 style parts, but in the direct CO2 branch.

Adafruit SCD-40 - True CO2, Temperature and Humidity Sensor

SCD-40 compact true-CO2 module with temperature and humidity. Direct CO2 branch, not comparable to eCO2 from SGP30/ENS160.

Adafruit ENS160 MOX Gas Sensor - Sciosense CCS811 Upgrade

ENS160 MOX gas sensor breakout with IAQ/TVOC/eCO2-style outputs over I2C. Good CCS811-style upgrade branch, not true CO2.

Adafruit ENS161 MOX Gas Sensor

ENS161 MOX gas sensor breakout, same broad indoor-air-quality branch as ENS160. Treat as a firmware/library change until checked.

Adafruit STCC4 and SHT41 - CO2, Temperature & Humidity Sensor

STCC4 plus SHT41 CO2/temperature/humidity module. Direct CO2 branch and cheaper/smaller than older SCD modules, but not a drop-in replacement for SCD-30/40/41 boards.

Adafruit PMSA003I Air Quality Breakout

PMSA003I particulate-matter breakout. Put it in the PM branch with SPS30/BMV080/SEN55-style sensors, not the VOC/eCO2 or true-CO2 branch.

Adafruit SGP40 Air Quality Sensor Breakout - VOC Index

SGP40 VOC-index breakout. Good sibling to other SGP40 boards; not a true-CO2 sensor and not a particulate sensor.

Adafruit SGP41 Multi-Pixel Gas Sensor Breakout - VOC & NOx

SGP41 VOC and NOx gas-sensor breakout. A stronger indoor-air-quality path than SGP40 when NOx matters, but still not a direct CO2 or PM sensor.

Grove - CO2 Sensor

Grove NDIR CO2 sensor module. Use when actual CO2 measurement matters; it is not interchangeable with eCO2/VOC-index breakouts.

Grove - Multichannel Gas Sensor v2

Grove multichannel gas sensor for CO, NO2, alcohol and VOC-style gas detection. Treat as a gas-family board, not true CO2 or particulate measurement.

Grove - SEN55 All-in-one environmental sensor - NOx, VOC, RH, Temp, PM1.0/2.5/4/10

Grove SEN55 all-in-one environmental sensor. Covers particulate matter plus VOC/NOx, humidity and temperature, so it can consolidate sensors but changes interface, enclosure and firmware work.

Grove - Smart Air Quality Sensor - SGP41

Grove SGP41 smart air-quality sensor. Similar sensing branch to Adafruit SGP41, but Grove connector/module format changes wiring and mounting.

MICS6814 3-in-1 Gas Sensor Breakout (CO, NO2, NH3)

MICS6814 gas breakout for CO, NO2 and NH3. Useful for multi-gas trend detection, not a substitute for true CO2 or particle sensors.