According to NFPA 25, the Standard for the Inspection, Testing, and Maintenance, of Water-Based Fire Protection Systems, periodically sprinklers are to be replaced or, in lieu of replacement, a minimum of 4 sprinklers or 1% of the sprinklers in a sample area are to be tested.  Unfortunately, the interval for this replacement/testing is not “one-size-fits-all” – it depends on a variety of factors including the sprinklers’ response type, age, and environment.

Figure 1 walks you through the replacement/initial testing intervals according to the most recent, 2023 edition of NFPA 25.  Note the following applicable definitions, which can all be found in Chapter 3, Definitions, in the standard:

  • Control Mode Specific Application (CMSA) Sprinkler. A type of spray sprinkler that is capable of producing characteristic large water droplets and that is listed for its capability to provide fire control of specific high-challenge fire hazards. (
  • Corrosion-Resistant Sprinkler. A Sprinkler fabricated with corrosion-resistant material, or with special coatings or platings, to be used in an atmosphere that would normally corrode sprinklers. (
  • Dry Sprinkler. A sprinkler secured in an extension nipple that has a seal at the inlet end to prevent water from entering the nipple until the sprinkler operates. (
  • Early Suppression Fast-Response (ESFR) Sprinkler.  A type of fast-response sprinkler that has a thermal element with an RTI of 50 (meter-seconds)1/2 or less and is listed for its capability to provide fire suppression of specific high challenge fire hazards. (

Unfortunately, NFPA 25 contains no definition of a harsh environment.  It does, however, give some examples in Annex A, Explanatory Material:

Examples of these environments are paper mills, packing houses, tanneries, alkali plants, organic fertilizer plants, foundries, forge shops, fumigation areas, pickle and vinegar works, stables, storage battery rooms, electroplating rooms, galvanizing rooms, steam rooms of all descriptions including moist vapor dry kilns, salt storage rooms, locomotive sheds or houses, driveways, areas exposed to outside weather, areas around bleaching equipment in flour mills, and portions of any area where corrosive vapors prevail. (A.

The maximum allowable ambient conditions also come into play when determining replacement/testing intervals.  This information can be found in Table 1 for your review.

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Table 1. Maximum allowable ambient conditions by temperature rating according to most current, 2023 edition of NFPA 25 Table

Figure 1. Sprinkler replacement/initial field service test intervals according to the most current, 2023 edition of NFPA 25.

While not part of NFPA 25 requirements, Dyne Fire Protection Labs also recommends identifying any sprinklers that may feature an O-ring water seal design.  Identification guides from various manufacturers and/or listing agencies can be found online.  This design has a notoriously high failure rate (>50%) and was the subject of several recalls in the past.  In other words, the chances of one or more sprinklers in a sample set of four or more failing is quite high.  Remember that NFPA 25 requires the replacement of all sprinklers represented by that sample set to be replaced if even just one fails.  As a result, outright replacement of O-ring designs is recommended. 

Should the sprinklers in the sample area be initially tested instead of replaced and if the testing found the sprinklers to still be acceptable (i.e. those sprinklers represented by the sample set tested remain in service), subsequent testing would then be needed periodically after.  Figure 2 walks you through the subsequent testing intervals according to the most recent, 2023 edition of NFPA 25.

Figure 2. Subsequent field service testing (where applicable) intervals according to the most current, 2023 edition of NFPA 25.

Why are sprinklers replaced/tested on different intervals?

Sprinkler replacement/testing intervals are largely impacted by historical data or the lack thereof.    For relatively newer technologies (e.g. fast response sprinklers) replacement/initial testing has been pushed back several years over the last several editions of NFPA 25 as data continues to grow to support such a move (i.e. failure rates at current rate continue to be low).  The same goes for dry sprinklers, which for a time were replaced/initially tested much sooner given the prevalence of the O-ring water seal design – a design that has now not been listed at UL in over 20 years.  While some O-ring designs do remain in the field, the numbers are dwindling, and as a result, the failure rates have dropped so much so that the replacement/initial testing of those sprinklers has also been pushed back over the last several editions.

For sprinklers in a harsh environment, degradation can obviously be greatly accelerated and thus the replacement/testing is due much sooner.  However, those sprinklers that are listed corrosion resistant are given a slightly longer time before replacement or testing is required given their use of corrosion-resistant material, coatings or plating to combat some of that degradation.

If you have any questions regarding this article, please contact Dyne Fire Protection Labs at or (800)632-2304.

©Dyne Fire Protection Labs 2023