This paper presents Sidh - a game based firefighter training simulator developed in cooperation between the University of Sk¨ovde and the Swedish Rescue Services Agency. Sidh is based on computer game hardware and software solutions but adds a novel interaction model and gameplay specifically developed for the purpose of training firefighters. The simulator environment is a Cave where the player is interacting with the game through a set of sensors. Players move in the virtual world by movements in the physical world and a substantial physical effort is required to accomplish game tasks. Sidh has been used in a feasibility study where 31 firefighter students have been playing the game and the performance of these students as well as their reflections from using the game have been analyzed. Results from this study show that Sidh is a useful complement to traditional training methods and that the subjects give very high grades on the entertainment value of the game which indicate that this form of training may be self-motivating which is an important issue for voluntary, after-hours training.