A Floating Production Storage Off-loading (FPSO) can be divided into four areas each with distinct characteristics of gas explosion development. The application of three generic types of gas explosion model is discussed. Suggestions are given for possible development of empirical and phenomenological models and the pitfalls associated with more flexible CFD codes are discussed. Experimental evidence and results of simulation show that there exists a. critical cloud size, which we called runaway length, above which gas explosion could develop rapidly leading to damaging over-pressure. The success of control measures need to take account of the runaway length, e.g. an effective measure could include diverting a gas leak towards an area with a larger runaway length. The main structural surface on FPSO is the hull which tends to be strong. Drag loading on pipework, equipment and grated decks could be more significant than simple over-pressure load. (C) 1998 Elsevier Science Ltd. All rights reserved.