The present invention reduces the amount of oxygen in an oxygen-containing gas
within a closed environment. A selected amount of hydrogen gas is mixed with a
portion of the oxygen-containing gas from the closed environment to form a first
gas mixture. A catalyst exposed to the first gas mixture causes a reaction between
the hydrogen and at least a portion of the oxygen therein. The resulting second
gas mixture, which is returned to the closed environment, has a lower percentage
of oxygen. At least one oxygen sensor is positioned in the closed environment to
determine when oxygen levels in the closed environment reach a threshold level.
The output signal from the sensor is used to control when and/or how much hydrogen
is mixed in the first gas mixture.