Method and apparatus for monitoring and measuring a gas

Method and apparatus for monitoring and signalling the quantity of a known gas, or gases, in a gas mixture is described. The monitoring system is particularly adapted to continuously sense the quantity of hydrogen or oxygen in the containment gas mixture for a nuclear reactor electrical power generator. The monitoring system utilizes thermal conductivity gas measuring cells arranged in an electrical bridge network along with a catalytic reactor for modifying the constituency of the containment gas mixture undergoing measurement to provide the signal representative of the changes in constituency of the containment gas mixture at the power generating site