Special fire sprinkler system installation guidance intended to guard against damage due to earthquakes first appeared in the North American sprinkler installation standard in 1947, and was largely based on experience in the Long Beach earthquake of 1930. At that time many building codes in use in the United States did not even address the subject of earthquakes. Insurance reports of the Long Beach earthquake had indicated 90 damaged sprinkler systems. The first guidance, contained only in the appendix, called for 1 to 2 inches clearance around pipes, flexible couplings in risers and some form of lateral and longitudinal bracing for feed and cross mains. In the 1951 edition requirements were placed in the body of the standard for placement of longitudinal and lateral braces with spacing indicated as 30 to 40 ft, a maximum slenderness ratio of brace members of 200, and flexible couplings on risers where it was necessary to protect systems against earthquakes. The stated intent was to laterally brace for 50% of weight of water-filled piping and attachments. In the decades since then deliberate efforts have been made to clarify the rules and improve protection within the text of NFPA 13 — Installation of Sprinkler Systems, but always with the intent of addressing how systems are to be protected against earthquakes, not where such protection is to be provided. It was recognized that building codes and other authorities made the basic decisions with regard to the location of earthquake-prone areas. Although the earliest guidance contained in NFPA 13 came from the insurance industry in the western states, the NFPA Committee on Automatic Sprinklers formed an Earthquake Protection Subcommittee in 1985. One of the goals of this subcommittee was to develop a means to address the bracing of sprinkler systems in the same manner that the application of system hydraulics had been accomplished. Although a complex subject, it was believed that many of the design aspects could be pre-engineered into tables and then properly applied by the technicians who normally lay out and detail fire sprinkler systems. The 1983 standard contained no information on the sizing or fastening of bracing relative to loads. A method was proposed in 1984 whereby zones of influence could be evaluated to determine total loads for proposed brace locations. Tables were proposed for determining maximum brace loads and allowable fastener loads based on six different combinations of brace and fastener orientation and angle from vertical. This concept and the accompanying tables were accepted into the appendix of the standard in the 1987 edition, and in the 1989 edition the tables were expanded to nine combinations of orientation and angle and moved into the body of the standard.