A number of different types of gas can be detected. They fall into the following categories:
Combustible gases
Combustible gases are sensed by the gas detectors covered in this project. They are gases which will burn.
Toxic gases
Toxic gases are poisonous to humans. The most common are carbon monoxide and hydrogen sulphide.
Oxygen
It is important that oxygen levels do not fall too low, for respiration purposes, but they also should not get too high, as this can increase the chance of explosion.
