"National Fire Protection Association (NFPA) 13, 'Standard for the Installation of Sprinkler Systems' requires fire sprinkler systems to be securely attached to the buildings they protect. The attachment is accomplished through various pipe hangers and bracing devices that are designed and installed to enhance the sprinkler system's survival during a fire, earthquake, windstorm or other events that may threaten a building. According to NFPA 13, 'risers' are the vertical supply pipes that distribute water to the overhead pipe network of cross mains and branch lines. They must be supported by riser clamps or, if the riser has a portion that runs parallel to the floor, by hangers located on the horizontal connections within 24 inches (610 millimeters) of the centerline of the riser."
Coffee Break Training - Fire Protection Series No. FP-2014-29
United States Fire Administration: http://www.usfa.fema.gov/