The sprinklers in these systems are attached to pipes containing pressurized water at all times. Individual sprinklers in the vicinity of a fire are set off by heat, allowing water to flow through them immediately. Wet pipe systems are used where 45 degrees(minimal) temperature is to prevent freezing. When water freezes it expands. If a pipe bursts due to freezing temperatures, it may disable the fire protection system and cause water damage. In the event that the fire sprinkler system is exposed to freezing temperatures, an antifreeze solution is added to certain sections in a wet-pipe system to prevent freezing.