The CGA400 is a system to maintain constant the comburity index/CARI of natural gas or a mixture of combustible gases through a comburity index/CARI analyser and an air injection control system.
 
Air is injected into the gas to regulate the comburity index/CARI to a level below the minimum value. The amount injected is controlled through two control loops, one on the variation of the gas comburity index/CARI and the other on real-time consumption of the plant that is followed by a gas meter.
 
The system provides a 4-20mA analog output corresponding to the comburity Index/CARI.