Operating Manual PG11 / PGE11 Page 12
3.2 Preparations and Positioning considerations
PG11 is a point gas detector and should be placed as close to a potential leaking point as possible. However,
each installation is different from another, and detailed considerations must be done locally in order to get
the best coverage for detection. Below are some general matters to consider:
● The detector should be placed where maintenance, such as cleaning of optics can easily be
performed.
● The relative weight of the target gas compared to air must be taken into account when deciding the
optimum installation height. Methane is lighter than air and in this case the gas detector may have to
be placed above a potential leak source. In case of the other hydrocarbons such as Propane being
heavier than air, could accumulate lower levels and might be better detected by placing Detectors at
lower levels - in many instances close to the floor.
● The concentration of a gas cloud will quickly reduce with the distance from the leak source. The
detector should therefore be placed as close as possible to potential leakage sources.
● In spaces where there are two main components of gas then it is recommended to use two gas
instruments in accordance with HAZOP studies or a Detector that is sensitive to both gases. The
Optical Methane Detector will for most heavy hydrocarbons react very strongly and might be
suitable.
● The detector should not be mounted in areas where it can be drenched by water.
● Also, the fact that gas quickly dilutes when released into the air, and the impact of wind must be
considered. As illustrated below with a leak point at position A, the gas will spread in the direction of
the wind and be detected at position C (downstream), but not detected at position B. The wind speed
has no effect on the detector.
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