Hazardous area classification on ships
Zone 0, 1 and 2 designation aboard ship, the equipment categories each zone demands, and the standards that govern the classification drawing.
Hazardous area classification divides the spaces of a ship into zones according to how likely a flammable atmosphere is to be present, and then fixes the certification an item of electrical or mechanical equipment must carry to be installed in each. It is a design control, recorded on an approved classification drawing, not an operational judgement made at the time.
The three-zone scheme distinguishes a continuously present atmosphere, one likely in normal operation, and one that is unlikely and short lived if it occurs at all. The consequence of the zone is the equipment category and protection concept permitted in it, which is why a change to a zone boundary is a change to the equipment list.
The full article will cover the source of release concept, the zone definitions and the standards that set them, equipment protection concepts and marking, the ship types where the classification is most consequential, and the survey and modification control that keeps the drawing true. See LNG fuel system and IGF Code .