Abstract: A fire prevention system is disclosed herein for external installation on a dwelling having an extended conduit closed at one end and detachably coupled to a source of pressurized water at its opposite end. A portion of the conduit is disposed along the highest part of the roof and is provided with a plurality of spaced-apart fluid discharge nozzles such as sprinklers. A smoke detector and sprinkler activator is operably connected to the conduit and is critically mounted on the exterior of the dwelling on the side thereof most likely to detect the presence of smoke. The windward side is an example. The activator includes solenoid operated valves responsive to the detector and further, a deactivate circuit is operably included for automatic shut-off.