- The Rayleigh refractometer utilises the refractive index of a gas to calculate its concentration.
- Thermal conductivity is used in katharometers. In these devices, the cooling of a wire causes a change in resistance proportional to gas concentration.
- Solubility is employed in devices such as rubber strips when an increase in length accompanies gas absorption.
- Light emission features in the Raman light scattering measurement device.
- Both infrared and ultraviolet absorption are used in gas concentration measurement.