Abstract: The concentration of gas is determined by monitoring the coloration of a reagent test paper, or the like, whose color changes progressively or otherwise in response to continued exposure to such gas. The concentration is determined by determining the length of time which the reagent test paper must be exposed to the gas for the coloration of the test paper to reach a preselected threshold value.

Abstract: An infrared gas analyzer is provided with a first path for reference radiation and a second path for measuring radiation. A source emits infrared radiation into the first and second paths. A detector arrangement is positioned at the ends of the paths for sensing the intensity of reference and measuring radiation passing through the paths. A radiation-travel-control arrangement alternately blocks one and then the other of the two paths and during the blocking of each path causes radiation directed towards the blocked path to be deflected into the unblocked path so that such radiation is not wasted.

Abstract: A non-dispersive infrared analyzer, particularly for determining the concentration of a gas in a gas mixture, including a source of infrared radiation, means for modulating the radiation beam, a test chamber in the path of the modulated beams and containing the gas to be analyzed; an absorption chamber in the path of the beams exiting the test chamber, including a forward and a rear portion through which the beams sequentially traverse; and a vaned adjustment structure located in the rear portion of the absorption chamber for adjusting the path length of the beams in the rear portion of the absorption chamber.

Abstract: A cylindrically shaped coil of resistance wire constitutes a source of infrared radiation which is located within a reflector comprised of a curved reflector section having a reflecting surface shaped to resemble an axially bisected rotationally symmetrical paraboloid, and a cylindrical reflector section which extends from an open side of the curved reflector section. The focal points of the reflecting surface are located on a circle which coincides with the outer circumference of the cylindrically shaped coil.