August 8, 2016
Ceiling Pocket Volumes “NFPA 13D limits the total volume of all unprotected ceiling pockets in a compartment to no more than 100 ft3 whereas NFPA 13 is limited to 1,000 sq.ft. Typically, NFPA 13 is more stringent. Please confirm the above references are accurate and, if so, please explain the intent of the wide variation between the volumes.” We have reviewed NFPA 13, 2013 edition and NFPA 13D, 2013 edition as the applicable standards. Our informal interpretation is that these volumes are as intended. You’re right that NFPA 13 is a more stringent document but that primarily means that it provides a longer lasting, more robust system along with extent of protected areas so as to provide life safety and property protection. It doesn’t mean that all aspects are more stringent. Ceiling pockets is a good example. The allowance for ceiling pockets was first added to NFPA 13 back in the 2002 edition based on fire modeling performed by AFSA. It was shown that large ceiling pockets (bigger than 1,000 sq. ft. and much deeper than 3 ft) could be unprotected and the adjacent quick response sprinklers in the lower ceiling would activate at least as fast as a standard response sprinkler in a flat ceiling. The requirement for QR sprinklers in a light hazard occupancy was only added in the 1996 edition so the acceptance of a standard response activation time was not an issue (keeping in mind that the reduction of the remote area for using QR sprinklers is not allowed). On the other hand, NFPA 13D?s use of residential sprinklers (as well of NFPA 13 section 8.10) has always been based on a fast response element. As such, they can’t tolerate a significant delay in activation times. Considering that ceiling pockets have become a prevalent feature, it’s desirable that it’s addressed by the standards. The technical committee accepted a proposal allowing 100 sq. ft. as a small enough volume so as to have minimal impact on the activation time. Don’t forget that an indentation of no more than 12 inches is not considered a ceiling pocket. NFPA 13 remains a more stringent standard even with larger ceiling pockets. ------------ Technical Update is prepared by the Technical Services Dept. of the AFSA: Roland Huggins, a PE registered in fire protection engineering, Vice President of Engineering and Technical Services; and Tom Wellen, a PE registered in fire protection engineering. This is provided with the understanding that the AFSA assumes no liability for this opinion or actions taken on it and they are not to be considered the official position of the NFPA or its technical committees. Copyright 2016, American Fire Sprinkler Association. All Rights Reserved. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.firesprinkler.org/private.cgi/sprinklernotes-firesprinkler.org/attachments/20160808/3219103e/attachment.htm>
