"The student shall be able to list several actions needed to avoid freeze-up emergencies in water-based fire protection systems. With the northern hemisphere in the middle of winter, sustained cold weather creates potential problems like this severely ice-damaged outside stem and yoke valve that was left in the open position when the building heat was turned off."
Coffee Break Training - Fire Protection Series No. 2007-8
United States Fire Administration: http://www.usfa.fema.gov/