Video - How Paint Affects Sprinkler Performance

The 2017 Edition of NFPA 25 Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems requires an annual floor level inspection per 5.2.1 and any sprinkler that shows signs of paint, other than that applied by the sprinkler manufacturer, must be replaced.  The reasoning behind this is that any paint applied after the sprinkler has left the manufacturing process could impact the performance in both the coverage pattern and thermal sensitivity.  Dried paint in the deflector could prevent water from reaching the desired areas during a fire and dried paint on the release mechanism or water seal could insulate or prevent release, respectively.

To illustrate the thermal sensitivity performance issues caused by aftermarket painting, sprinklers with and without paint were tested at Dyne Fire Protection Labs in the Plunge Test Oven to determine response time.  Three different types of sprinklers were chosen to illustrate that paint can affect different thermal response elements.  Figure 1 shows the sprinklers chosen for this study.

Each sprinkler type was plunged four times with and without paint to show repeatability.  The painted sprinklers were entirely painted with one coat of flat white Rust-Oleum Painter’s Touch 2X general spray paint.  The oven was set at 135±1°C with an air flow of 2.5±0.1 m/s and the sprinklers were plunged with a similar response time plunge test method as outlined in UL 199 and FM 2000.  A video of the testing for this study can be viewed on Dyne’s YouTube page.  The results of the plunge tests are shown in Figure 2.

Based on these results, paint clearly has an effect on the response time of the sprinkler but the results are quite varied.  Some sprinklers didn’t release at all when fully painted and several only had a partial release (pressure loss was detected but the waterway didn’t fully clear due to parts of the release mechanism and/or water seal remaining in place).  Note, however, that some sprinklers with paint still performed just fine.  For the quick response sprinklers tested, all fully released and only one sprinkler did not go off in the required amount of time to meet the quick response definition.  While some may argue that this is reason for NFPA to allow small amounts of paint on the sprinkler, at this time and with the current information available, it is too much of a risk to allow any aftermarket paint which is why NFPA requires that a sprinkler with any amount of paint must be replaced.  There is significant variability in the performance of aftermarket painted sprinklers and there is potential for even a drop of paint in the right spot to impact thermal performance.  The exception to being paint only on the sprinkler arms which would not impact the coverage pattern or thermal response, so sprinklers with this paint may not need to be considered for replacement during the floor level inspection.

Should you have any questions about these results or periodical sprinkler testing in general, please contact Dyne at (800)632-2304 or