The ULTRAMAT 6 single-channel or dual-channel gas analyzers operate according to the NDIR two-beam alternating light princi­ple and measure gases highly selectively whose absorption bands lie in the infrared wavelength range from 2 to 9 ?m, such as CO, CO₂, NO, SO₂, NH₃, H₂O as well as CH₄ and other hydrocarbons.