US Patent 8663996 Determining oxygen concentration in ullage using catalytic oxidation

A system for measuring the oxygen concentration of a gas includes a catalytic reactor, first and second temperature sensors and a control unit. The catalytic reactor includes a combustion catalyst that supports the catalytic combustion of hydrocarbon fuel vapor in a gas stream. The first temperature sensor is located upstream of the catalytic reactor for sensing an upstream temperature of the gas stream, and the second temperature sensor is located downstream of the catalytic reactor for sensing a downstream temperature of the gas stream. The control unit compares the upstream temperature and the downstream temperature to determine the oxygen concentration of the gas stream.