Author(s): Matt Klaus. Published on October 30, 2014.

IN ITS MARCH/APRIL 2014 COVER STORY, “Safety by Design”, NFPA Journal looked at the challenges facing big-box retailers to provide sprinkler protection for their facilities. One of the more difficult issues for these retailers has been identifying protection schemes for certain storage arrangements not addressed by NFPA 13, Installation of Sprinkler Systems.

The ultimate test for these rack storage arrangements is the protection of exposed, expanded Group A plastics, typically Styrofoam or similar products. If a sprinkler system can protect these materials, the thinking goes, it can protect just about anything. Full-scale testing of this arrangement has been around for some time, but the data have not been made available to the NFPA 13 technical committees. As a result, the standard has not addressed a protection scheme for this arrangement, and it has not addressed other, less extreme arrangements that could be protected following the guidelines for exposed, expanded Group A plastics.

Until now. Thanks to the efforts of the Fire Protection Research Foundation and the Property Insurance Research Group, full-scale testing of exposed, expanded plastics in racks was conducted between 2012 and 2014. The project, which included a total of eight tests of bagged polystyrene foam meat trays on wooden pallets, was developed to provide the NFPA 13 technical committees with data on ceiling-only sprinkler protection schemes for this difficult storage arrangement. The tests looked at varying ceiling and storage heights, clearances between the stored plastics and the ceiling, and the use of vertical barriers as a way to prevent horizontal spread of fire through the racks.

The critical piece of data from this testing was the number of sprinklers that operated during each test. This is information that, along with the test set-up parameters, is used to create an acceptable protection scheme in NFPA 13. The number of activated K-25 ESFR (early suppression, fast response) sprinklers ranged from six to 18. In three tests, 10 or fewer sprinklers activated, and these tests were reviewed by the technical committee as the basis for new language in the standard. The committee typically adds a “safety factor” of 50 percent to the test data, and the initial design considered 15 sprinklers.

The drawback of this approach, however, was that a 15-sprinkler design using K-25 sprinklers with a 60 psi operating pressure would call for a tremendous amount of water. In an effort to reduce the hydraulic demand for this arrangement, an additional test was scheduled. In that test, conducted in June, only seven sprinklers operated; the technical committee now had three tests in which seven or fewer sprinklers activated.

Applying the safety factor of 50 percent allowed the committee to review and approve a 12-sprinkler, ceiling-only design for the protection of exposed, expanded Group A plastics, based on a maximum storage height of 25 feet for single-, double-, and multiple-row rack configurations. The concept must go through the NFPA 13 correlating committee and the NFPA Annual Technical Meeting in Chicago in June 2015, but it appears that NFPA has added an important component to the standard.

This change has ramifications for a number of stakeholders. A new design scheme for protecting exposed, expanded Group A plastics will allow almost anyone who utilizes high-ceiling rack storage arrangements—manufacturers, distributors, retailers, and others—greater flexibility in the packaging of their products, which translates to more efficient warehousing operations and cost savings through the reduction of storage space and packaging materials. The testing project also provides an ideal example of how research supports the development of codes and standards.

Matt Klaus is NFPA's Principal Fire Protection Engineer.