New Rules for Smoke Detectors

At first glance, it appears that there are many changes to the spot-type smoke detection section of Chapter Five in NFPA 72, 2007 Edition. After a quick check of “Smoke-Sensing Fire Detectors,” section 5.7, you will notice there are no dots indicating...


At first glance, it appears that there are many changes to the spot-type smoke detection section of Chapter Five in NFPA 72, 2007 Edition. After a quick check of “Smoke-Sensing Fire Detectors,” section 5.7, you will notice there are no dots indicating text was moved/removed, but you will notice a dozen or so vertical lines alongside the rules in this important section.

For those not familiar with the layout of the codes and NFPA standards, a line is used to denote changes from the previous edition. In this case, the previous edition is from 2002. The line is made vertically, in the margin alongside the passage in which the changes were made. (The hardbound, illustrated Handbook version uses an icon next to the paragraph stating “New,” but unlike the standard softbound edition, they do nothing to indicate something is missing.)

In the section being discussed here, two of these change lines are rather long, and along with the other ten lines, seem to indicate substantial changes have been made to the 2007 edition. Or have they? NFPA doesn't make it easy when they don't say what the change is, exactly. The changes can only be found by carefully comparing the text from the previous edition (or reading a comprehensive technical article in your favorite trade magazine by yours truly). Most of the lines indicating changes are nothing more than fine-tuning, and are neither changes nor additions. For instance, in section 5.7.3.2.3.2 the word “documented” is replaced with “published” and now reads, “In all cases, the manufacturer's published instructions shall be followed.” The change from using “documented” to “published” added about four feet of vertical lines in the margins of the 2007 edition of NFPA 72.

Another section that seems to have been re-worked to incorporate additional requirements brings up the concepts of performance-based and prescriptive-based layouts – neither of which is new. NFPA 72, 2002 at 5.7.3.2.3.1 stated that smoke detectors shall be permitted to be located using a 30-foot spacing as a guide . The 2007 change now has that section beginning with “In the absence of specific performance-based design criteria…” This means that now, when you are required to comply with the 2007 edition, you must either designate your detector placement layout as “performance based” or use the simple, prescriptive, 30-foot spacing. The “as a guide” has been dropped. The very next rule, 5.7.3.2.3.2, still states that “in all cases” the manufacturer's instructions must be followed. I'm guessing that manufacturers will all state it should be a guide .

That thinking seams logical; that is until you get to the next rule, which was left unchanged, and turns the 30 foot back into “a guide”: “5.7.3.2.3.3 Other spacing shall be permitted to be used depending on ceiling height, different conditions, or response requirements.” Confused? Expect more vertical lines in future editions when they try to better explain these 2007 changes.

FYI: If you want to submit performance-based information you would need to provide for review and approval “…documentation, in an approved format, of each performance objective and applicable scenario, together with any calculations, modeling, or other technical substantiation used in establishing the proposed design's fire and life safety performance.” The following must be evaluated :

(1) Structural features, size, and shape of the rooms and bays

(2) Occupancy and uses of the area

(3) Ceiling height

(4) Ceiling shape, surface, and obstructions

(5) Ventilation

(6) Ambient environment

(7) Burning characteristics of the combustible materials present

(8) Configuration of the contents in the area to be protected

Real changes were made to section 5.7.3.2.4 regarding spacing to be used in rooms or spaces with solid joist or beam construction. To show the changes, I have inserted the 2002 wording in brackets, next to the underlined 2007 wording.

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