You need to make a judgement based on the definitions of Zone 0, 1, 2 - the definitions are given in the DSEAR guidance books that can be downloaded from the HSE website. Zone 0: An area in which an explosive gas atmosphere is present continuously or for long periods; Zone 1: An area in which an explosive gas atmosphere is likely to occur in normal operation; Zone 2: An area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time. Around the tanks and pipelines - probably Zone 2 I wouldn't classify around the actual burner - its meaningless, as that is the intended use of the propane etc You obviously need to ensure there is adequate ventilation at all times - to prevent the build up of an ex atmosphere. Without knowing the pressure of the gas, can't really say what the extent of the haz zone will be - but probably in the region of 2-3m. If you use continuous welded pipe, that cuts down on the sources of release and hence need to classify BS60010-10 gives more guidance on determining Zone classification & ventilation requirements and safe distances.