Air Quality Module MQ-135: The Air Quality Module MQ-135 is a sensor module that is used to detect various air pollutants such as ammonia, nitrogen oxides, benzene, smoke, and others. The module features a high sensitivity and fast response time, making it ideal for air quality monitoring applications.

Features:

• Sensor module for detecting air pollutants
• High sensitivity and fast response time
• Suitable for air quality monitoring applications

Specifications:

• Detection gas: ammonia, nitrogen oxides, benzene, smoke, and others
• Sensitivity: 0.1-10ppm
• Operating voltage: 5V DC

An example how to use it: http://wiring.org.co/learning/basics/airqualitymq135.html

An example with calculation of the CO2 value: http://davidegironi.blogspot.it/2014/01/cheap-co2-meter-using-mq135-sensor-with.html

Search for datasheet: http://duckduckgo.com/?q=%22mq135%22+gas+sensor+filetype%3Apdf

source
http://playground.arduino.cc/Main/MQGasSensors