by Russell Fleming, P.E.
From the new issue of NFPA Journal®
While the “small room rule” has been around for 40 years, it remains a source of confusion in the application of NFPA 13, Installation of Sprinkler Systems. The rule is never clearly stated but exists as a combination of special allowances made for rooms no larger than 800 square feet (74.3 square meters) in size.
One area of confusion is between the small room rule and the “room design method.” The room design method is an alternative to the use of a density/area method when deciding which sprinklers constitute the “design area,” the reasonably worst-case arrangement of sprinklers expected to operate simultaneously during a fire. The size of the design area determines the minimum water supply for the area.