Heath Consultants Remote Methane Leak Detector Intrinsically Safe (RMLD-I) - Manual (Page 29)

The invisible Infrared (IR) detector laser beam is transmitted from the launch port. With
a normal background, such as brick, concrete, and grass, it has a maximum distance of up
to 100 ft. away (actual distance may vary due to surface condition).
Fig. 4-4
To detect leaks, as the above illustration depicts, when the infrared laser beam passes
through a gas plume, and is reflected back, the reflected light is collected and converted
to an electrical signal that carries the information needed to deduce the methane
concentration.
The laser light is selective to methane, and will not false-alarm on other hydrocarbons.
This signal is processed so that methane concentrations can be reported in parts-per-
million-meter or ppm-m.
Ppm-m is the product of the methane concentration times the width of the plume. For
example, if the leak is creating a gas cloud of 1000 PPM and is about ½ meter in width
(the distance the infrared beam passes through the plume). The RMLD-IS will measure
500 ppm-m.
For another example, if the average concentration of the gas cloud is 20 PPM and is
about two (2) meter in width, the RMLD-IS will measure 40 ppm-m, plus a background
level of 15 ppm-m in this case, displaying a total value of 55 ppm-m.
101296-0 RMLD IS MANUAL REV J
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