All sprinklers are required to have a Sprinkler Identification Number (SIN). The SIN is comprised of one or two letters followed by three or four numbers. The requirement for this SIN is found in NFPA 13, Installation of Automatic Sprinklers, as well as UL and FM sprinkler product standards. This requirement was implemented as of January 1, 2001. Therefore, sprinklers manufactured prior to 2001 may not have this mark on them.


sample SIN: RA7216

.The goal behind the use of the SIN is to ensure proper use of the sprinklers in the field. Specifiers, design engineers, and layout technicians can check the proposed use of a sprinkler against its capabilities. In addition, the SIN can be used after a system has been installed to assist inspectors in determining if a system is adequate. On a long term basis the SIN can help with proper replacement sprinklers when they are necessary. Previously, sprinkler markings were not especially helpful to anyone trying to identify the type of sprinkler with which they were dealing.

The original concept of the SIN was to create a unified model numbering system to assist the end user and authorities with easy identification in the field. However, this was soon realized to be impractical. The vast number of variations and the fact that the same product could have different classifications from different laboratories prohibited this concept from proceeding.
Every change in orifice size, response classification, distribution characteristic, and maximum working pressure must be identified by a separate model number. This system has not been established to create uniformity of model numbers among the manufacturers. For example, Model AB120 could be one manufacturer’s standard response K-5.6 (K-80 metric) upright spray sprinkler, while Model BC120 could be another manufacturer’s K-14 (K-200 metric) pendent ESFR.

The letters in the SIN represent the manufacturer of the sprinkler. Their one or two letter code must be registered with the International Fire Sprinkler Association at Each manufacturer is permitted a maximum of two different letter designations. However, there are also limitations on the possible letter combinations. First, the letters are limited to the English alphabet. Also, there is a list of letter(s) (shown in the table below) that are prohibited due to conflicts with established acronyms relative to the fire sprinkler industry (such as laboratories, K-factors, sprinkler orientations or hazards).

The three or four numbers are the model numbers and are set by the manufacturer themselves. Some manufacturers use each digit to represent a characteristic of the sprinkler, while others use it strictly as a cataloging number.