An Informal Interpretation from the American Fire Sprinkler Association: “What is the definition of corrosion? If a sprinkler head is chrome and has turned green but does not have any build up on the sprinkler head is this corrosion? Does this sprinkler head have to be replaced?”
We have reviewed NFPA 25, 2011 edition as the applicable standard. Our informal interpretation is that any amount of corrosion should be considered unacceptable.
There is no definition in NFPA 25 for corrosion. The dictionary should be referenced when NFPA does not define a term. The online version of Webster’s Dictionary indicates that corrode is to eat away by degrees as if by gnawing; to wear away gradually usually by chemical reaction; to weaken or destroy gradually. Thus if a sprinkler head turns green, it is likely a form of corrosion. Section 22.214.171.124.1 of NFPA 25 indicates that sprinklers shall be free of corrosion. This means that any amount of corrosion is unacceptable according to the standard. Any other literature dealing with sprinkler systems and inspections also says that corrosion of the sprinkler is unacceptable. Manufacturer’s data sheets for sprinklers require that any corroded sprinklers be replaced, and normally the warranty is voided for corroded sprinklers. If corrosion is a persistent problem, the building should be installed with listed corrosion-resistant sprinklers (see NFPA 13, 6.2.6 in the 2010 edition).
The annex material to further addresses corroded sprinklers in A.126.96.36.199. If the sprinklers are lightly corroded, it could be permitted for continued use if samples are selected for testing based on worst-case conditions and the sample successfully pass the test.