Gas sensors are devices that detect the presence of various gases within an area, usually as part of a system to warn about gases which might be harmful to humans or animals. Gas sensors can be used to detect combustible, toxic, and oxygen and CO2 gases. This device may be used in firefighting.

For gas sensor applications with a constant heat source, the power output of the TEG needs to match or exceed the power input requirements of the sensor. If the heat source is variable, the TEG can be used to trickle charge a battery that powers the gas sensor directly.