Heath Consultants Optical Methane Detector (OM) - Manual (Page 9)

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auto exhaust and swamp or sewer gas. Due to the selectivity of the
OMD, false positives caused by auto exhaust are greately mini-
mized.
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Experienced operators should use their discretion. Operators
should take into account that the wind must be favorable,
towards the path of the OMD light bar, to obtain the optimum
results. Increased speed from FID survey comes from the
instantaneous response of the OMD; however, there are a
variety of factors to consider such as, legal limits, terrain and
inclement weather for the OMD operation. Please refer to
the GPTC Guide for Transmission and Distribution Piping
Systems: 1998-2000 Guide Material Appendix G-192-11
Section 4 Leak Detection, 4.4 Leakage surveys and test
methods (a) Surface Gas Detection Survey. Part (3) Utiliza-
tion. The use of this survey method may be limited by ad-
verse conditions (such as excessive wind, excessive soil
moisture or frost or surface sealing by ice water). The survey
should be conducted at speeds slow enough to allow an
adequate sample to be continuously obtained by placement of
equipment intakes over the most logical venting locations,
giving consideration to the location of the facilities and any
adverse conditions which might exist.
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VERVIEW