According to the current, 2020 edition of National Fire Protection Association (NFPA) 25 Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, a representative sample of sprinklers for the field service testing shall consist of a minimum of not less than four sprinklers or one percent of the number of  sprinklers per individual sprinkler sample, whichever is greater (

Sample Area

NFPA 25 does not define what an individual sprinkler sample should be.  The area represented by a sprinkler sample set should be defined by the property owner or their designated representative.  For example, the building owner or designated representative could define their sample area by each sprinkler system.  However, it is also just as valid to expand the sampling area and define it as the entire building even if made up of multiple systems.  Likewise, the building owner or designated representative could certainly narrow the sample area and define it by environment, by floor, or even by room if they so choose.  Obviously, narrowing the sample size down too far can be unreasonable.  For instance, sampling and testing four sprinklers from a room with only six sprinklers to begin with wouldn’t make much sense.  In this scenario, it would be more cost effective just to replace all six sprinklers.

Expanding the sampling area too wide can also have financial consequences.  According to, “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.”  Should there be one failure in the sample group, there is a high probability that there would be other sprinklers in that same area that fail as well.  The larger the area a sample set of sprinklers represents, the more sprinklers there may be to replace should even just one sprinkler at the laboratory fail the field service test.  Defining the sample area is a balancing act between the cost of testing versus the cost of potential replacement should a sprinkler(s) fail.

It is always advised to define sample areas based on environments since the environment a sprinkler is stored in will have a great impact on its lifespan.  For instance, consider a building with a conditioned office and unconditioned warehouse.  It would be appropriate to classify the warehouse and office areas as two different sprinkler sample sets and send in at least four sprinklers or one percent (whichever is greater) of the sprinklers from each area.  If this is done and a warehouse sprinkler were to fail the field service test due to the harsh environment it is in, only the warehouse sprinklers would need replacement.  The office sprinklers, which would most likely be in a much different condition since they have been stored in a conditioned space their whole life, would not need replacement because they were represented by a different sample set.

Different Types of Sprinklers within a Sample Area

After defining the individual sprinkler sample areas, four sprinklers or one percent of the sprinklers in that area (whichever is greater) must be sent in for testing.  The sprinklers chosen should be selected at random and not selected simply because of their accessibility.  Note that the floor level inspection as defined by shall be done and those sprinklers that clearly fail the floor level inspection should be replaced before sampling of sprinklers for the field service test (A. 

If there are different types of sprinklers in the area, each sprinkler type should be represented in the sample provided to the laboratory.  It is important that every type of sprinkler is represented in the sample in case one of the sprinkler types was more susceptible to the environment than the others.  Note that each orientation of a sprinkler (upright, pendent, sidewall) does not need to be included in the sample (A.  The orientation of the sprinkler by itself will not change the field service test results.  Sprinklers that were made by a different manufacturer, are a different model, and/or feature a different water seal, release mechanism, and/or finish should all be represented in the sample.

Should the sample area contain more sprinkler types than the minimum number of sprinklers required to be sampled (four or one percent, whichever is greater), NFPA 25 A. states that additional sprinklers should be included in your sample set if needed to have all sprinklers represented.  The four or one percent requirement is a minimum requirement and there can certainly be scenarios where more sprinkler samples are needed to get a better representation of the area.  For example, if there are five different sprinkler types in a defined sample area which features less than four hundred sprinklers in total, it is not possible to have all five types of sprinklers represented in just four samples.  Additional sprinklers beyond the minimum of four would be required to have all sprinklers represented in such a sample set.

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

©Dyne Fire Protection Labs 2020