Abstract: A detector module for use in a gas monitor assembly to measure changes in electron flow resulting from absorption of electrons in an electron capture gas includes an internal housing for containing a radioactive source and electrodes suitably spaced apart to permit gas flow therepast. The internal housing along with couplings for interconnection with a gas flow source, a gas receiver and suitable electronic receiver means are disposed within a detector housing having integrally attachable closure means, the detector housing and closure means providing shielding for the radioactive source while being adapted in combination to prevent operating access to the couplings in order to prevent accidental or undesired exposure of the internal housing and radioactive source.

Abstract: A gas monitor comprising means for detecting changes in electron flow between two electrodes caused by absorption of the electrons by an electron capture gas flowing between the electrodes. A carrier gas is supplied to the detecting means at a predetermined velocity. A sample of the gas to be measured is added to the carrier gas by a valve means at a predetermined time which gas sample contains a trace of a first type of electron capture gas. The carrier gas together with any gas sample flows through a column means which slows down the velocity of any other type of electron capture gas in the sample with respect to the velocity of the first type of electron capture gas. The gas then passes through the detector wherein the electron capture gas causes a decrease in the electron flow between the electrodes. Means are provided for measuring the maximum decrease in the electron flow caused by the first type of electron capture gas and means are coupled to the measuring means for indicating the maximum decrease.