Premature sprinkler activation can be a frustrating and costly situation. At Dyne Fire Protection Labs, we often get inquiries from exasperated individuals who have just experienced premature sprinkler activation (and the water damage associated with it) about whether or not Dyne can determine the exact cause of the activation. Unfortunately, we cannot. Dyne Fire Protection Labs’ well known field service testing is only designed to fulfill NPFA 25’s periodical testing requirements, specifically section 5.3.1.1 of the current, 2020 edition of NFPA 25. As stated in the Annex of the 2020 edition of NFPA 25, section A.5.3.1.1, this routine periodical testing is designed to determine thermal sensitivity (adequate response time) and functionality (waterway clears). Each sprinkler sent in for this testing is plunged into an oven and the time at which the sprinkler activates is monitored. The requirement is that the activation time, the time at which the release mechanism activates and the waterway clears, is such that the resulting Response Time Index (RTI) is less than the RTI requirements established by the 2020 edition of NFPA 25. The longer it takes for a sprinkler to activate, the higher the RTI value. For more information on RTI calculations and the current requirements, please review Dyne’s technical article titled Sprinkler Sensitivity Requirements published in April 2019. Note that the sensitivity requirements have no minimum. While a sprinkler that activates much quicker than expected can be a warning sign for potential premature activation, there would be no failure for a sprinkler that activates quicker than expected during the routine field service testing.
What kind of testing can be done to determine if a sprinkler may activate prematurely?
If a sprinkler has truly activated, the release mechanism has responded to a temperature lower than its listing. Therefore, the testing to identify sprinklers that may activate prematurely should be designed to determine the temperature of activation. This is different than the routine field service testing described in NFPA 25 which determines the time a sprinkler takes to go off at one specific temperature.
If you have experienced a sprinkler that has activated prematurely, you may be concerned the other sprinklers in the area may also activate prematurely and want to verify the activation temperature. Unfortunately, Dyne does not advertise activation temperature testing as part of our normal list of services. To accurately determine the activation temperature, the rate of temperature increase must be very gradual. This means the time to test each sprinkler for activation temperature can take several hours. Since our laboratory specializes in quick turnaround for routine field service testing, utilizing our plunge test oven for several hours can be quite costly and time consuming. As such we cannot perform such testing under our normal 5 business day turnaround guarantee. While this testing does not appear on our advertised list of available services, it may still be possible to contract Dyne Fire Protection Labs to perform this work. Please contact us for more information.
Once a sprinkler has activated prematurely, is there any testing that can be done to determine why?
The activation temperature testing described above is only useful if a sprinkler is suspected of being compromised but it does nothing to determine the reason for sprinklers that have already prematurely activated. If the sprinkler features a soldered release mechanism and the pieces of the sprinkler post activation can be found and collected, it may be possible for a laboratory to analyze the solder for solder creep and/or corrosion. Solder creep occurs when a sprinkler is exposed to temperatures above the maximum ceiling temperatures listed in Table 7.2.4.1 of the 2019 edition of NFPA 13:
Exposure to these high temperatures, while not enough to cause activation, can weaken the solder over time. The solder weakens as it gets close to the listed activation temperature. Not enough to fully release, but enough to become slightly malleable.
In addition to solder creep, corrosion of the solder can also weaken the release mechanism over time. FM Global data sheet 2-1, Corrosion in Automatic Sprinkler Systems, discusses this in detail starting on page 57 under section 5.6 “Corrosion and Premature Operation of Sprinklers.” We typically only think of corrosion as seizing the metal links and/or the water seal together (leading cause of sprinkler failure during field service testing) but corrosion can also weaken the solder and cause premature release.
Dyne does not offer the testing to identify the phenomena above. The manufacturer or the listing agency of the sprinkler may offer this kind of analysis if they deem such analysis necessary after better understanding your situation.
How do I get the manufacturer involved?
The quickest way to involve the manufacturer is by contacting and explaining your situation to their technical services department.
How do I get UL involved?
You can report a concern that a UL listed product did not perform as designed via their online Market Surveillance Form.
How do I get FM involved?
You can report a concern with a FM Approved product by emailing information@FMApprovals.com. Please provide as much detail as possible in the email regarding the product and issue.
Some things to consider before requesting forensic analysis of an activated sprinkler.
The questions below are based on the release mechanism of the sprinkler that activated prematurely.
If your sprinkler features a glass bulb release mechanism:
1. If the sprinkler(s) that activated prematurely were installed fairly recently, could the bulbs have been damaged between leaving the manufacturing plant and being installed (i.e. dropped)? Dropping of a glass bulb sprinkler can cause very small fractures in the glass which weaken it, allowing activation at a much lower temperature. This type of damage would typically cause premature activation relatively quickly after install.
2. If the sprinkler(s) that activated prematurely were installed some time ago, is there any chance the sprinklers were damaged right before the activation event? Forklifts, ladders, coat hangers, etc. are all common culprits but there have even been situations where video evidence showed a bird pecking out the glass bulb.
If your sprinkler features a soldered mechanism (link, pellet, etc.):
1. Have the sprinkler(s) that activated prematurely ever been exposed to high temperatures above the allowed/designed maximum ceiling temperature? See Table 7.2.4.1 in the 2020 edition of NFPA 25. Consider that HVAC exhausts potentially could be increasing the temperature of only a specific area of the ceiling leading to isolated instances of premature activation.
2. Does there appear to be corrosion around the release mechanism of the sprinkler(s) that activated prematurely? If corrosion is apparent and you can’t explain why (i.e. you wouldn’t consider the area the sprinkler is in corrosive), have the sprinklers ever been exposed to harsh chemicals? Harsh acidic/basic chemical vapors could erode the solder over time. Situations have been noted where sprinkler(s) prematurely activated shortly after fumigation for instance
For more information on other sprinkler mishaps, see Dyne’s technical article titled Common Mysterious Sprinkler Mishaps & Possible Causes which was published August 2018.
If you have any questions regarding this article or have a question that you would like to see addressed in a future article, please contact Dyne Fire Protection Labs at lab@dyneusa.com or (800) 632-2304.
©Dyne Fire Protection Labs 2019