4.2　Process Plants

4.2.1　Distance between a detection point and a release source in outdoor equipment areaor equipment area in open workshop should meet the following provisions:

1　When the detection point is set on the windward side of the annual minimum wind frequency of the release source，the distance between a combustible gas detection point and a release source should not exceed 15m and that between a toxic gas detection point and a release source should not exceed 2m.

2　When the detection point is set on the leeward side of the annual minimum frequency wind direction of the release source，the distance between a combustible gas detection point and a release source should not exceed 5m and that between a toxic gas detection point and a release source should not exceed 1m.

4.2.2　When the release source of combustible gas is in a closed or poorly ventilated semi-open workshop，a detector may be set every 15m.The distance between a combustible gas detector and any release source within its detective range should not exceed 7.5m and that between the toxic gas detector and the release source should not exceed 1m.

4.2.3　When the release source of combustible gas or toxic gas lighter than air is in a closed or partially poor ventilated semi-opened workshop，in addition to equip detectors above the release source，gas detectors shall be equipped at the highest points in the workshop prone to gas accumulation.