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UL urges testing of dry sprinklers

NOTE: This information is from a previously printed press release, newsletter, or other dated document. It is presented here for archival purposes only.

NORTHBROOK, Ill., March 3, 2000 - Underwriters Laboratories Inc. (UL) is urging property owners whose buildings are equipped with dry sprinklers that have "O-ring" water seals to have samples of those sprinklers tested immediately. These sprinklers may not operate in the event of a fire because they may require higher water pressures to operate than may be available in the building.

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

UL strongly recommends that building owners and managers whose buildings are equipped with dry sprinklers immediately contact their sprinkler installation and maintenance companies to assess the installation(s) in question and determine the appropriate corrective actions, including replacement.

As announced by UL on Jan. 22, 1999, laboratory testing indicates that these sprinklers may not operate in the event of a fire because they may require a higher pressure to operate than is available in some buildings. UL has received recent reports of incidents in which dry sprinklers failed to operate in a fire, resulting in property damage.

The results of UL's on-going investigation, and input from community 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, reduced the time interval for testing or replacement of these sprinklers from 50 years to 10 years after they have been in service. However, recent data indicates that immediate testing of dry sprinklers equipped with "O-ring" water seals is advisable. Several locations equipped with sprinklers in service less than 10 years have required elevated water pressures to operate.

To date, UL has conducted operational tests on more than 300 samples taken from more than 40 different installation locations. These tests indicate that 49 percent of the samples required pressures greater than seven pounds per square inch (psi) to discharge water and 20 percent required pressures greater than 40 psi to discharge water from the sprinkler.

The installation requirement for water pressure established by the NFPA is 7 psi. A pressure of 40 psi may exceed the water pressure available in some locations.

According to UL vice president, Jim Beyreis, "The majority of dry sprinklers manufactured during the past 30 years have employed the use of an 'O-ring' water seal. Many of these 'O-ring' sealed sprinkler constructions have not operated properly because the water seal assembly stuck and did not allow water to flow."

Considering the environmental conditions many of these sprinklers may be exposed to, Beyreis indicated that a frequent test or replacement interval is necessary to provide the desired level of protection. "Several sprinkler samples did not operate as intended because of exposure to harsh environmental conditions," said Beyreis.

Any dry sprinkler, regardless of construction type or year of installation, showing signs of corrosion should be replaced. In light of the most recent data, UL urges immediate testing or replacement of dry sprinklers incorporating an "O-ring" water seal regardless of the year of manufacture or installation location. 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. Before representative sprinkler samples can be submitted to UL for testing, it is important to consult directly with the sprinkler manufacturer or through their customer service representatives for information regarding removal and replacement of the test samples, as well as the applicable terms of the manufacturer's warranty.

Once samples have been properly removed and packaged according to the instructions, sprinkler samples can be sent directly to Mr. Kerry Bell at Underwriters Laboratories Inc. (UL), 333 Pfingsten Rd., Northbrook, Ill., 60062 (phone: +1-847-272-8800, ext. 42629; e-mail: for operational testing. In keeping with UL's not-for-profit, testing for public safety mission, UL will conduct these operational tests at no cost to the submitter during the course of UL's investigation, with the exception of expenses related to sprinkler removal, replacement, shipping and handling.

"Fire sprinklers have an excellent field record and have saved countless lives and reduced property damage," said Beyreis. "UL is investigating the continued reliability of sprinklers equipped with O-ring water seals, because of recent field reports and the associated tests results, and is considering a proposal to revise the appropriate UL Standards for Safety with respect to O-ring water seals."

UL is an independent, not-for-profit, global product safety testing and certification organization that has been dedicated to public safety for more than 106 years. UL has been investigating and Listing automatic sprinklers for fire protection for more than 90 years. For a copy of this release, or to obtain further information about UL, visit our Web site at