Operational testing of sprinklers: UL Solutions explains NFPA 25 sample testing rules
Iain Hoey
Share this content
Kerry M. Bell, principal engineer, Fire Sprinkler and Pump Equipment at UL Solutions, sets out testing procedures and clarifies temperature rating considerations for varied installation environments
For several decades, UL Solutions has examined and tested sprinklers sampled from field installations in accordance with the recommendations and requirements of applicable National Fire Protection Association (NFPA) standards.
To be effective in controlling or suppressing a fire, a sprinkler system is required to be designed and installed to provide protection against the magnitude of the fire risk anticipated to occur.
For example, the amount of water required to be discharged from a sprinkler protecting a warehouse with high-piled storage is multiple times greater than the amount of water required to be discharged from a sprinkler protecting an office facility with a smaller fire load.
While it is critical for sprinkler systems to be properly designed and installed, it is equally important for these systems to be periodically inspected, tested and maintained to help ensure that the system equipment will perform as intended if a fire occurs.
The primary focus of this article is on the examination and testing of the sprinklers sampled from a sprinkler system as referenced in the 2023 edition of NFPA 25, Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems.
Inspection, testing and maintenance requirements for sprinklers
Periodic inspection of field-installed sprinklers is an important element of a comprehensive maintenance program for fire sprinkler systems.
As specified in NFPA 25, sprinklers showing signs of leakage, field painting, physical damage, loss of fluid in the glass bulb heat responsive element and corrosion or loading considered detrimental to sprinkler performance must be replaced.
These conditions can lead to the degradation of sprinkler performance during a fire condition.
In addition to the periodic inspection of field-installed sprinklers, the 2023 edition of NFPA 25 also requires replacement or representative sample testing of sprinklers based on the length of time in service.
Sample testing or replacement frequency depends on the sprinkler type and installation environment.
While many sprinklers do not require representative testing or replacement until they have been in service for 50 years, sprinklers having fast response elements must be tested or replaced at a shorter time interval.
Early suppression fast response (ESFR) and control mode specific application (CMSA) sprinklers that have fast response elements must be tested or replaced after 20 years in service and 10-year intervals thereafter.
Other types of sprinklers that have fast response elements must be tested or replaced after 25 years in service and 10-year intervals thereafter.
Due to the relatively complex construction of a dry-type sprinkler, as well as some of the challenging installation environments where many of these sprinklers may be installed, dry-type sprinklers must be tested or replaced after 20 years of service and 10-year intervals thereafter regardless of the sprinkler response type.
It is also worth highlighting the fact that NFPA 25 indicates that sprinklers installed in extraordinarily harsh environmental conditions, such as foundries, fertiliser facilities or areas exposed to outside weather conditions, must be replaced or representative samples tested on a five-year basis.
The frequency for sample testing or replacement of some of these sprinklers has been revised over the years in consideration of the overall performance during representative sample testing.
Sprinkler samples selected for testing are to be representative of the sprinklers installed in the system.
As noted in NFPA 25, no less than four samples, or 1% of the number of sprinklers per sample area, whichever is greater, are to be tested.
The sprinkler samples removed from the system for testing must be immediately replaced with new sprinklers.
Each sample received by UL Solutions is visually examined before testing to ascertain the sprinkler manufacturer, model or sprinkler identification number, style, type of heat responsive element, temperature rating and year of manufacturer.
The condition of the sprinkler is also noted based on visual evidence of corrosion, loading, leakage, physical damage, loss of fluid in a glass bulb heat responsive element or field painting.
The testing of the sprinklers involves an assessment of the ability of the sprinkler to operate and allow the discharge of water.
Sample testing and report
To assess the operating characteristics of sprinklers sampled from field installation environments, the samples are subjected to the sensitivity-oven heat test as described in ANSI/CAN/UL/ULC 199, the Standard for Automatic Sprinklers for Fire Protection Service.
During this test, the inlet of the sample is pressurised to approximately 5 psi (0.35 bar) and quickly plunged into an oven that circulates heated air at a constant temperature and velocity.
The actual temperature and air velocity used for the test are selected based on the temperature rating of the sprinkler.
Each sprinkler sample is observed for proper operating characteristics including the release of operating components and time of operation.
If the heat response element functions but the water seal does not release, the sample is exposed to a water supply to determine if the sprinkler’s water seal releases at 7 psi (0.5 bar).
The test report for the samples is provided to the submitter and describes the condition of each sprinkler and results of the operation test as either normal or abnormal.
The as-received condition of each sprinkler sample described in the report is based on a visual examination.
The information included in the report is intended to be considered by other parties in determining the need to replace other sprinklers in the system.
UL Solutions
UL Solutions is a global leader in safety science with deep expertise in the Built Environment industry.
We provide comprehensive testing and certification services for fire protection products, including sprinklers, supporting manufacturers throughout the entire product lifecycle, from design and development to compliance and market entry.
Our rigorous evaluation processes help demonstrate safety, reliability, and performance, enabling manufacturers to meet regulatory requirements and gain access to global markets with confidence.