| 摘要 |
A device for detecting small amounts of alkanes such as methane, ethane, propane, and butane gases, comprising an optical waveguide and a light source for propagating light therethrough; apparatus for obtaining samples of air to be tested; apparatus for adding water vapor to these air samples to yield gas mixtures with at least a 30% relative humidity; and means for flowing these mixtures over the surface of the optical waveguide at a rate sufficient to favor condensation of the mixture on the waveguide surface to thereby form a thin film thereon. The presence of alkanes is determined by detecting the intensity of the light after propagation through the optical waveguide and then comparing that detected intensity to a reference. In a preferred embodiment, the optical waveguide is an optical glass capillary in which the surface is closed in a lens-like configuration at the detector end.
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