Heath Consultants Remote Methane Leak Detector Intrinsically Safe (RMLD-I) - Manual (Page 30)

Fig. 4-5: The ppm-m reading is the product of the plume concentration times the distance the IR
beam passes through the plume (plume width) in addition to any background gas. As the scan
distance increases, the size of the infrared beam “footprint” increases.
The infrared beam width is about 22” at 100 feet. It is important to note that the laser
beam “footprint” width and distance increases as the distance increases (see Figure 4-5).
This is why it is much easier to detect leaks from a distance of 10 to 15 feet and beyond.
**Note**
There is always a small amount of methane in the air. This natural methane background
is also measured by the RMLD-IS. The ppm-m reading will then increase as the
scanning distance increases.
**Note**
The nature of a gas plume is highly variable. The above illustrations are intended to
convey the basic theory. Some leaks may have a high surface concentration with little to
no measurable plume above the surface.
101296-0 RMLD IS MANUAL REV J
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