Abstract: As an important equipment room in medical buildings, the equipment in the linear accelerator room is expensive and the radiation protection in the installation space requires special requirements. It put forward different conventional requirements for firextinguishing system design. According to the principles of safety, applicability and economy for fire extinguishing system selection, this paper briefly analyzes various kinds of fire extinguishing systems.It put forward the applicability and reasonableness of applying water mist fire extinguishing system. The paper suggested using high pressure water mist fire extinguishing system of single interlocking preaction system in linear accelerator.Taking the linear accelerator room of a medical center as an example,introduce the design of its high- pressure water mist fire extinguishing system from the aspects of system selection, application mode and design parameters.In this paper, some problems concerned in the design, such as the misprision, the pressure particle size, and the design parameters of the system, and some notable problems are discussed.

Key words: linear accelerator room, water mist fire extinguishing system, medical building