application_number US 85636304 A description as shown in fig1 a self calibration gas sensor 10 has a housing that for example may be in the form of a can 12 that is covered at its open end by a cover 13 the can 12 and the cover 13 for example may be made of nickel plated steel the can 12 holds a substance 14 such as water or water gel or hydrophilic oxides like silica gel in an antiseptic solution the substance 14 provides a source of water vapor for the self calibration gas sensor 10 as shown in fig1 the substance 14 has a level 16 although the can 12 can contain more or less of the substance 14 other materials can be used for the substance 14 depending upon the particular application temperature range for the self calibration gas sensor 10 a support plate 18 is provided in the can 12 above the level 16 of the substance 14 the support plate 18 has a hole 20 therethrough to permit the flow of vapor from the substance 14 through the support plate 18 the support plate 18 for example may be a stainless steel washer a gas detector 22 is supported by the support plate 18 the gas detector 22 for example may be in the form of.