A device for automatic, real time monitoring of carbon monoxide and for providing a continuous read out of the concentration of carbon monoxide. The monitoring device includes two Y-cut, temperature sensitive quartz crystals which are encapsulated in a helium filled can. One of the cans containing a quartz crystal is surrounded by a wire mesh which carries a thin layer of hopcalite coating. The hopcalite is used for oxidizing the carbon monoxide and the resulting heat of the reaction is detected by the temperature sensitive crystal. Each crystal is driven by a conventional crystal controlled oscillator circuit with a constant frequency bias of a few hundred Hz. The frequencies of the two oscillator circuits are fed into a conventional mixer circuit which beats the frequencies together and produces a single net frequency which is the difference between the two frequencies. The net frequency signal is converted to a D.C. analog voltage signal which is then fed into a suitable display device for providing a continuous readout of the concentration of carbon monoxide.

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