Abstract: A diffusion-type NDIR gas analyzer with an improved response time due to convection flow created by a temperature gradient between gas located within a waveguide and gas located within a diffusion pocket of space created between the waveguide and a semi-permeable membrane which surrounds the waveguide. The temperature gradient may be created by a thermally resistive radiation source that is not thermally isolated from the waveguide. The semi-permeable membrane is made of a hydrophobic material and has a thickness sufficient to provide its own structural integrity. The semi-permeable membrane can have a porosity less than approximately 50 microns and be comprised of ultra high molecular weight polyethylene or Teflon®.

Abstract: A power circuit for use with a resistive thermal radiation source in which the power delivered to the resistive thermal radiation source will remain constant within a preselected deviation over a fixed period of time as the source resistance of the source varies between an initial source resistance and a second source resistance at the operating temperature. The power circuit is designed to maintain constant power within a preselected deviation by using the resistance of the resistive thermal radiation source to calculate a preselected resistance used in the power circuit according to the following equation: ##EQU1## wherein .DELTA.P=P.sub.si -P.sub.s ; P.sub.si =the initial power on the resistive thermal radiation source; P.sub.s =the power on the resistive thermal radiation source when the source resistance is equal to the second source resistance; K.sub.1 =RO/R.sub.si ; R0=the preselected resistance; R.sub.si =the initial source resistance; K.sub.2 =R.sub.s /R.sub.si ; and R.sub.

Abstract: A fire detector with a maximum average response time of less than 1.5 minutes is obtained by combining a smoke detector with a CO.sub.2 detector that uses NDIR sensor technology. The smoke detector is used to detect smoldering fires and to help prevent false alarms attributable to the CO.sub.2 detector. The CO.sub.2 detector is used to rapidly detect fires by measuring the rate of change of CO.sub.2 concentration. A signal processor generates an alarm signal when a smoldering fire is detected or alarm logic indicates that a fire has been detected.

Abstract: A fire detector having a greatly reduced frequency of generating false alarms. An AND gate is responsive to outputs from first and second fire detector modules that are responsive to the detection of first and second characteristics of a fire, respectively, to signal the detection of a fire if both of these characteristics have been detected. At least one override path is included to enable the occurrence of a particular type of fire to be signaled that would not otherwise be signaled by the output of said AND gate.

Abstract: A fire detector with a maximum average response time of less than 1.5 minutes is obtained by combining a smoke detector with a CO.sub.2 detector that uses NDIR sensor technology. The smoke detector is used to detect smoldering fires and to help prevent false alarms attributable to the CO.sub.2 detector. The CO.sub.2 detector is used to rapidly detect fires by measuring the rate of change of CO.sub.2 concentration. A signal processor generates an alarm signal when a smoldering fire is detected or alarm logic indicates that a fire has been detected.

Abstract: Multichannel infrared detector assemblies for use in the detection and monitoring of gas concentrations are provided.

Abstract: A fire detector which combines an NDIR CO.sub.2 gas detector with a photoelectric smoke detector to minimize false alarms by logic means that can be integrated into a single chip that can have an ASIC section and a microprocessor section. The NDIR CO.sub.2 detector can be single or dual channel. The NDIR CO.sub.2 gas detector and the photoelectric smoke detector can be separate or combined in a single device in which they are optically isolated by a light-tight barrier but still use a common light source. Also, the CO.sub.2 and smoke detectors can be combined on a single substrate within a common housing.

Abstract: A passive source infrared gas detector which uses an ambient temperature source and the space between the detector assembly and the source as the sample chamber is provided, the gas detector includes an infrared detector assembly for producing a first output, a second output, and a third output, the first output being indicative of the radiation received by the detector assembly at a first non-neutral spectral band which is absorbable by a preselected gas to be detected, the second output being indicative of the radiation received by the detector assembly at a first neutral spectral band from the passive infrared source, and the third output being indicative of the radiation received by the detector assembly at a second neutral spectral band from the passive infrared source. Signal processing means are included for manipulating the three outputs to determine the concentration of the gas being monitored.