Abstract: A buoy comprising a hydrocarbon processing facility for processing production fluids received from an offshore well, the facility being disposed in a portion of the buoy that is submerged below the waterline, has a pressure relief channel for venting gas above the waterline. The pressure relief channel is in fluid communication with a chamber in the buoy which may contain the processing facility, or other equipment presenting an explosive hazard, and is the only conduit through which high pressure is exhausted. In particular, the pressure relief channel can contain the effects of an over-pressurisation event within the chamber such as ignition of flammable gas, and mitigate structural damage to the buoy.