The detector is no more than one-half its listed spacing from any wall measured at a right angle.
Assuming we have a heat detector that has a listed spacing of 30 feet, the illustration above shows that we have followed both requirements. (2) All points on the ceiling shall have a detector within a distance equal to or less than 0.7 times the listed spacing (0.7S). (1) The distance between detectors shall not exceed their listed spacing, and there shall be detectors within a distance of one-half the listed spacing, measured at right angles from all walls or partitions extending upward to within the top 15 percent of the ceiling height. Following the spacing rules of NFPA 72įollowing the spacing rules of NFPA 72, Chapter 17, specifically Section 17.6.3.1.1, we know our detector layout must follow one of the two requirements below. References to NFPA 72 refer to the 2016 edition When we previously discussed fire alarm detector layout, we went through a series of square rooms/spaces to demonstrate how to place spot type fire alarm detectors, as shown in the example below.
