Fire Prevention & Protection, Fireground Safety

UL Continues to Urge Inspection and Testing of Dry Sprinklers

Northbrook, Ill., Dec. 21, 2001 – Underwriters Laboratories Inc. (UL), is again reminding property owners whose buildings are equipped with dry sprinklers that have “O-ring” water seals to have samples of those sprinklers inspected and tested immediately. Based on ongoing research, UL has found that these sprinklers may not operate in a fire because they may require water pressures higher than those available in the building to operate.

UL has tested more than 700 dry sprinkler samples, from numerous manufacturers, that had been removed from more than 100 different installation locations. Approximately 50 percent of the samples tested required inlet pressures greater than 7 psi to discharge water; about 22 percent required an inlet pressure of greater than 40 psi to discharge water.

UL has also received reports of ice forming within the internal waterway of some dry sprinklers installed within freezers. Based on the information available, UL engineers believe that ice inside the sprinkler assembly may contribute to undesired sprinkler discharge and may inhibit sprinkler operation in a fire condition.

Accounting for less than three percent of all installed fire sprinklers, dry sprinklers are generally found in locations such as attics, carports, cold storage structures, parking garages, warehouses, and unheated portions of buildings that have harsh environmental conditions characterized by wide variations in temperature, humidity, and corrosive conditions.

Any dry sprinkler that shows signs of corrosion, regardless of construction type or year of installation, should be replaced, says UL. Dry sprinklers installed within freezers should be inspected for evidence of ice forming within the waterway.

The results of UL’s ongoing investigation and input from fire safety experts led to a revision to the National Fire Protection Association (NFPA) 25, Standard for Inspection, Testing and Maintenance of Water-Based Fire Protection Systems. The revision, which became effective Aug. 9, 1999, requires that dry sprinklers in the field be tested after 10 years of service. However, recent data indicate that dry sprinklers equipped with “O-ring” water seals should be tested immediately.

UL has disseminated several public notices concerning the operating performance of certain sprinklers and has recommended specific precautionary actions, including those relative to dry sprinklers on Jan. 22, 1999 and March 3, 2000. On July 27, 2001, UL announced several revisions to its sprinkler standards, including those for dry sprinklers, that specified additional performance and construction requirements.

Central Sprinkler Company has a voluntary replacement program in place for several dry sprinklers including those manufactured by Star Sprinkler Company. The voluntary replacement program represents two of the numerous dry sprinkler brands tested. Additional information regarding this replacement program can be obtained by visiting:

Building managers and property owners can verify whether the sprinklers in question utilize “O-ring” components by contacting the sprinkler manufacturer or UL. Building owners desiring to have installed sprinklers tested should have representative samples of these sprinkler models removed from the installation and sent to UL for testing. UL will conduct these operational tests at no cost during the course of its investigation; there will be charges for sprinkler removal and replacement and for shipping and handling.

UL recommends that sprinkler manufacturers or their customer service representatives be consulted for information regarding the proper removal of the test samples and the applicable terms of the manufacturer’s warranty before the samples are removed to be sent to UL for testing. The sprinkler samples may be sent to Kerry Bell at Underwriters Laboratories Inc. (UL); 333 Pfingsten Rd., Northbrook, Ill. 60062. For additional information, call (847) 664-2629 or e-mail: [email protected].