Obstructions and ESFR Sprinklers - Phase 1

Fire Protection Research Foundation report: "Obstruction and ESFR Sprinklers - Phase 1" (PDF, 652 KB)
Author: Garner A. Palenske, P.E., William N. Fletcher, Aon Fire Protection Engineering Corporation
Date of issue: October 2014


ESFR sprinklers are often installed in warehouses to avoid installation of in-rack sprinklers. However, since the discharge pattern of ESFR sprinklers is different from standard-spray sprinklers, obstructions near the sprinkler heads can greatly affect the distribution of water. NFPA 13, Standard for the Installation of Sprinkler Systems, generally allows the following obstructions in Sections,, and 

  • Sprinklers installed per the allowable distances from near or at ceiling obstructions in Table
  • Isolated obstructions less than 2 feet wide and 1 foot or greater horizontally from sprinkler
  • Isolated and continuous obstructions less than 2 inches wide and 2 feet or greater below deflector or 1 foot or greater horizontally from sprinkler
  • Continuous obstructions 1 foot or less in width and located 1 foot horizontally from sprinkler
  • Continuous obstructions 2 feet of less in width and located 2 feet horizontally from sprinkler
  • Bottom chords of bar joists or open trusses located 1 foot or greater horizontally from sprinkler (upright sprinklers can be installed over the bottom chords of bar joists or open trusses that are up to 4 inches wide) 

Two methods are available in NFPA 13 to resolve obstructions that do not fall into the categories above: eliminating the obstruction or adding sprinklers underneath the obstruction. However, there have been some successful tests that have been conducted with obstructions that are not allowable by NFPA 13 without taking these measures. The information from these tests as well as information gathered from further testing could help inform revisions to the NFPA 13 requirements. 

The Fire Protection Research Foundation initiated this project to ultimately develop a tool that can be used for providing reliable analysis of the impact of obstructions on ESFR sprinklers based on existing test data and develop technical basis to the NFPA 13 Technical Committees for new requirements and guidance. The goal of this first phase project was to gather available test data, analyze the knowledge gaps, and develop a research plan for future testing.