After a fire, all sprinklers affected by the incident shall be replaced according to the current, 2023 edition of NFPA 25, the Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems. Note this includes more than just those sprinklers that activated.
Any soot-covered sprinklers should also be replaced. The soot, which is typically acidic in nature, can corrode/damage a variety of materials. As such, it can be detrimental to sprinkler performance.
Also consider any sprinklers, especially those immediately surrounding those sprinklers which activated, that may have been exposed to excessive temperatures (Table 1) during the incident. While temperatures just below a sprinkler’s temperature rating may not be enough to have caused activation, they may have been enough to still weaken the release mechanism which could lead to premature activation in the future.
The authority having jurisdiction (AHJ) will ultimately need to determine which sprinklers need to be replaced following a fire. If there is any question as to whether or a not a sprinkler has been compromised, laboratory testing could prove useful. Note that the sprinkler testing requirements (e.g. when to test, how many to test, what tests need to be done, etc.) described in section 5.3.1 is for routine purposes only. Nonroutine testing outside these requirements can certainly be done to address specific situations. According to A.5.3.1, “The type of tests to be conducted and the number and location samples to be submitted should be appropriate to the problem discovered or being investigated and based on consultation with the manufacturer, listing agency, and the authority having jurisdiction.”
Replacement sprinklers should be of the same make and model or have compatible performance characteristics:
- Orifice size/K-factor
- Temperature rating
- Coating (if any)
- Deflector type (e.g., upright, pendent, sidewall)
- Design requirements
Additional sprinkler replacement requirements can be found in section 18.104.22.168.
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