| 摘要 |
An improved apparatus is provided for detecting the presence of small concentrations of one gas, e.g. a poisonous or other noxious gas, in another gas, e.g. air. The gaseous mixture, e.g. contaminated air is caused to contact a colorimetric detector, e.g., an enzyme, supported on or in a support surface. The improvement involves having a sampling head for the vapor detection apparatus including (a) a detection chamber; (b) an opening permitting the insertion of a vapor detector into the detection chamber; (c) an inlet to the detection chamber, such inlet including a critical orifice directed towards the detection chamber; (d) an outlet from the detection chamber; (e) an interrelated coordination of the orifice diameter and the pressure drop across the orifice to cause a gas to pass through the critical orifice at a jet stream velocity approaching the velocity of sound, at that temperature (f) a vapor detector adapted to be positioned in the detection chamber via the opening (b), and (g) an air by-pass interconnecting the inlet and the outlet such that, in operation most of the air stream is directed from the critical orifice against, but not through the detector, and through the air by-pass through the outlet.
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