MQ-3 Gas and Alcohol Vapor Sensor Module - Waveshare 9530

Methane sensor module made in MEMS technology. It allows gas detection in the range of 1 to 10000 ppm and has an analog output. DFRobot SEN0565

Module with a smoke concentration sensor made in MEMS technology. It allows gas detection in the range of 10 to 1000 ppm and has an analog output. DFRobot SEN0570

Module with a formaldehyde sensor made in MEMS technology. It allows gas detection in the range of 0 to 3 ppm and has an analog output. DFRobot SEN0563

Module with ethanol sensor made in MEMS technology. It allows gas detection in the range of 1 to 500 ppm and has an analog output. DFRobot SEN0569

Module with nitrogen dioxide sensor made in MEMS technology. It allows gas detection in the range of 0.1 to 10 ppm and has an analog output. DFRobot SEN0574

Formaldehyde sensor (HCHO) dedicated to measuring ambient air quality. It is used to detect whether the surrounding environment exceeds a set concentration threshold. It is powered by a voltage of 5 V to 24 V and has an output in the form of a two-state digital signal. DFRobot SEN0595

Module with a CO2 sensor based on the XENSIV PAS CO2 system from Infineon. It enables precise measurement of CO2 concentration in ppm via I2C, UART and PWM interfaces. SparkFun SEN-2295

Digital sensor dedicated to measuring carbon dioxide (CO2), air temperature and relative humidity. High performance, fast response and excellent stability make it an ideal solution for a variety of applications such as greenhouses, cities, poultry farms and transport stations. Seeed Studio 101991029

A digital gas and air quality sensor that measures eCO2, TVOC, and the AQI air quality index. The device utilizes metal-oxide technology with four sensor sections and an embedded microcontroller, simplifying operation and integration with Arduino, Raspberry Pi, and CircuitPython platforms. The sensor supports I2C and SPI interfaces, as well as temperature and humidity compensation using an external sensor. The compact design and STEMMA QT/Qwiic standard allow for easy integration into projects. Adafruit 6431

A compact 3-in-1 module that simultaneously measures CO₂ concentration, temperature, and humidity. With 2.4 GHz Wi-Fi connectivity and MQTT and REST API support, it easily integrates with IoT systems and cloud platforms. It offers local data storage, a built-in web server, and an RGB indicator for air quality. Numato Lab NLSENZA002

An environmental sensor based on the BME688 sensor, enabling simultaneous measurement of temperature, humidity, atmospheric pressure, and air quality. The device detects volatile organic compounds and calculates CO₂ equivalent and IAQ, allowing for accurate monitoring of indoor conditions. Communication via an I2C interface ensures easy integration with microcontrollers and platforms such as Arduino and UIFlow. M5Stack U169

SGP41 gas sensor module for VOC and NOx measurement with I2C interface and STEMMA QT/Qwiic connectors, equipped with dual MOX sensing elements. Adafruit 6455

6-in-1 environmental sensor module enabling measurement of HCHO, TVOC, CO, IAQ, temperature, and humidity via UART communication. Provides high sensitivity thanks to electrochemical technology and compatibility with platforms such as Raspberry Pi, Arduino, and ESP32, making it suitable for air quality monitoring and IoT applications. Waveshare Environment X6 Sensor

Ozone (O₃) sensor breakout featuring an MQ131 sensing element, an analog AO output and a digital DO output. An onboard potentiometer allows adjustment of the digital output threshold. The module operates from a 5V supply and can be used in ozone monitoring projects and systems working with ozone generators. Soldered 333110

Carbon monoxide sensor breakout featuring an MQ7 sensing element, an ATtiny404 microcontroller and an I2C interface. Two Qwiic connectors enable solderless connection to a compatible controller board, while onboard switches allow the I2C address to be changed. The module operates from a 3.3V supply and detects the presence of CO and changes in its level in the air. Soldered 333121