"In July 2001, Central Sprinkler Company, an affiliate of TYCO Fire Products LP of Lansdale, PA, in cooperation with the Unites States Consumer Product Safety Commission (CPSC) announced a recall to replace 65 different models of Central type sprinkler heads--using O-ring type water seals--totaling approximately 35 million Central fire sprinklers. Under certain circumstances, especially with lower water pressures, these sprinklers may fail to operate during a fire. Unfortunately, not all of these sprinklers have been replaced and there are many still putting lives and property at risk. These O-ring model sprinklers were installed in a wide variety of buildings including homes, apartments, hospitals, day-care facilities, schools, dormitories, nursing homes, supermarkets, hotels, parking garages, warehouses, and office buildings. In addition, they may be concealed-- by design--with a ceiling plate to appear more aesthetically pleasing."
Coffee Break Training - Fire Protection Series No. 2007-3
United States Fire Administration: http://www.usfa.fema.gov/