By Grant Lobdell, President, Dyne Fire Protection Labs
as published in the January 2025 FPC magazine on page 15
About five percent of the sprinkler samples tested by Dyne Fire Protection Labs (“Dyne”) do not pass the testing requirements set forth by NFPA 25, Inspection, Testing and Maintenance of Water-Based Fire Protection Systems, and require replacement.
Section 5.3.1.1 “[At the intervals specified in NFPA 25], sample sprinklers shall be submitted to an approved testing laboratory for field service testing”
Section A.5.3.1.1 “…Sprinklers that have passed the visual inspection should then be laboratory tested for sensitivity and functionality…The waterway should clear when sensitivity and functionality is tested at 7 PSI…The thermal sensitivity should be such that the RTI does not exceed 350 (meters-seconds)1/2 for standard-response sprinklers, 65 (meters-seconds)1/2 for quick response and residential sprinklers, and 50 (meters-seconds)1/2 for ESFR sprinklers....”
Section 5.3.1.3 “Where one sprinkler within a representative sample fails to meet the test requirement, all sprinklers within the area represented by that sample shall be replaced.”
Let’s look at the most common reasons why a sprinkler fails this testing:
- Corrosion – Corrosion around the water seal is the most common reason for sprinkler failure. While the release mechanism may activate on time, the water seal does not release. Corrosion, whether internal or external, and the byproducts it creates has fused the water seal to the frame. The environment the sprinkler is in can contribute to accelerated external corrosion while internal corrosion can be accelerated based on water supply quality. Regarding external corrosion, pay careful attention to isolated corrosion only around the water seal itself, which could indicate the water seal is not sealing properly (leaking). Sprinklers that show signs of corrosion detrimental to sprinkler performance shall be replaced during the annual floor level inspection. (5.2.1.1.1)
- Loading – Loading refers to any foreign material that has found its way onto the sprinkler. Depending on its makeup and its location on the sprinkler, loading can adhere components, disrupt spray patterns, or at the very least act as an insulator, delaying release. For this reason, any sprinkler that shows signs of loading detrimental to sprinkler performance shall be replaced at the annual floor level inspection. (5.2.1.1.1) Note, however, that “in lieu of replacing sprinkler that are loaded with a coating of dust, cleaning the sprinklers with compressed air or a vacuum is permitted, provided that the equipment does not touch the sprinkler.” (A.5.2.1.1.1)
- Paint - A special type of loading that is particularly good at adhering. Paint located in the deflector can affect the water distribution pattern while paint on the release mechanism or water seal could help hold those components in place. Of course, as with all loading, it can also act as an insulator and delay release if located around the release mechanism. According to the latest addition of NFPA 25, paint, other than that applied by the sprinkler manufacturer, detrimental to sprinkler performance shall be replaced during the annual floor level inspection. (5.2.1.1.1)
- Loss of fluid in a glass bulb heat-responsive element - As the fluid in a glass bulb heat-responsive element heats up, it expands. Eventually, enough heat and expansion has occurred to break the glass bulb (activation) holding back the water seal. Loss of fluid in a glass bulb creates an air pocket for that expansion to grow into, thus delaying or even preventing release if that air pocket is big enough. Any sprinkler that shows signs of a loss of fluid in the glass bulb heat-responsive element shall be replaced. (5.2.1.1.1)
- O-Rings – About 5% of the sprinklers received by Dyne Fire Protection Labs in 2024 featured an O-ring water seal design. O-rings designs have a notoriously high failure rate (+50%), failing to release when activated. As a result, a sprinkler featuring an O-ring water seal design has not been listed at UL in over 20 years. Be on the lookout for this design during your annual floor level inspections. It should be replaced upon discovery.
Questions? Contact us today by calling (800) 632-2304 or emailing lab@dyneusa.com.
©Dyne Fire Protection Labs 2025