While fires in underground car parks are a relatively rare event, the damage resulting from them can be significant and in some cases fatal. Due to the rather high thermal load, they can last for hours, putting both the structure of the building and the lives of the fire fighters at risk. Detecting a fire incident as early as possible will help reducing damage considerably. Sprinkler systems (often the minimum requirement by prescriptive codes) cannot not offer early warnings. Only a performance-based design approach with an added detection system insures that fires are detected at an early stage. But, conventional point type heat detectors, installed in the harsh environment of an underground car park, will drive the cost for maintenance up.