The point-type infrared detector design is available from a number of manufacturers; a few are listed below: • Det-tronics (Detector Electronics) • Draeger • Emerson • General Monitors (Mine Safety Appliance [MSA]) • Honeywell • Pemtech • Safety Systems Technology • Sensor Electronics • Sierra Monitor Corporation • Simark Controls. Figure 30. Gas detector calibration tubing. Photo from Gladstein, Neandross & Associates, NREL 44684 Combustible gas detectors should be located near the highest point of the structure’s ceiling. The number, loca tion, and spacing of detectors must be determined by a registered/licensed design engineer and approved by the AHJ.
Figure 29 displays a ceiling-mounted, combustible gas detection head. example, the detectors can be calibrated by using tubing connected to the system at ground level to direct a cali bration trace gas toward the unit (Figure 30). The smell of the mercaptan in natural gas is a good indicator of a leak, but is only qualitative. Hand-held portable methane detectors are a quantitative method for identifying a leak. They are designed for localized gas detection and are a useful tool for technicians to have available when performing work in major vehicle repair garages because they provide a level of redundancy when working on the fuel system components.
An example of a hand-held portable methane detector is shown in Figure 31. The readings of the detectors should be used with care, as they are prone to false positives. For this reason, they should be used in conjunction with other leak detection methods when work is being per formed on vehicle fuel systems. Also, the smell of the mercaptan in natural gas is a good indicator of a leak, but is only qualitative. Combustible gas detectors should be located near the highest point of the structure’s ceiling. The number, location, and spacing of detectors must be determined by a registered/licensed design engineer and approved by the AHJ.
Because gas detectors are located on or near the build ing’s ceiling, it is beneficial to select detectors that can be calibrated without requiring direct access to the unit. For Figure 29. A ceiling-mounted combustible gas detection head. Photo from Gladstein, Neandross & Associates, NREL 44683 Figure 31. Typical hand-held portable methane detector. Photo from Gladstein, Neandross & Associates, NREL 44691 COMPRESSED NATURAL GAS VEHICLE MAINTENANCE FACILITY MODIFICATION HANDBOOK 20