Grill the Fire Expert: Sending Signals and Detector Coverage

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The Test Answers

Q: If a fire alarm control panel uses two phone lines and a DACT, NFPA 72 states it must send test signals on both lines. How does the digital communicator know which phone line to use for its 24-hour tests since my panel’s DACT alternates using each line for every signal it transmits? What if a fire drill gets it out of order and the same line test two nights in a row?

A: NFPA 72, 2002, allows seven different back-up transmission methods for the DACT’s primary method of a single phone line connected to the “public switched network.” In rule “Transmission Channels,” it states in (B) (2) that “both channels shall be tested at intervals not exceeding 24 hours.”
Then Exception No. 2 modifies this rule for when a second phone line is used for the back-up method: “Where two telephone lines (numbers) are used, it shall be permitted to test each telephone line (number) at alternating 24-hour intervals.” This saves you and your remote station from having two signals sent every night.
True, when a trouble, supervisory, or alarm signal is sent during the day, then it could cause the fire panel to use the same phone line it used the previous night to send the next 24-hour test signal. However, there’s an NFPA 72 rule that states that if any other type of signal is transmitted during that 24-hour period, then the panel doesn’t have to send a test signal during that same 24-hour period.
“DACT Transmission Means” ( says: “Each DACT shall automatically initiate and complete a test signal transmission sequence to its associated DACR at least once every 24 hours. A successful signal transmission sequence of any other type within the same 24-hour period shall fulfill the requirement to verify the integrity of the reporting system….” Your daytime fire drill would use the second line and fulfill that night’s test requirement.

Required by Definition?

Q: My local building official refers to a passage in NFPA 72 that requires complete coverage when installing smoke detectors. Can you go over what this is?

A: There is a section in 5.5.2 of NFPA 72 that describes all places you must install detectors for “complete coverage.” This is merely a definition that escaped being placed in the definition chapter. NFPA 72 doesn’t require “complete coverage” and never has. This passage is for occasions when another document/person uses this language, so you know what would be required.
The description from Chapter 5 for Total (Complete) Coverage reads: If required, and unless otherwise modified by through, total coverage shall include all rooms, halls, storage areas, basements, attics, lofts, spaces above suspended ceilings and other subdivisions and accessible spaces as well as the inside of all closets, elevator shafts, enclosed stairways, dumbwaiter shafts and chutes.

(Note: The “unless otherwise modified” language refers to exceptions for six areas to be protected under
The passage starts off with “if required,” but the AHJ doesn’t require anything — they enforce what’s required by the law, as spelled out in the adopted codes. The rules are meant to be applied only when required by those codes. Just because you can find a passage/definition, it doesn’t become a requirement for every fire alarm system. You can only be made to install the minimum protection spelled out for each occupancy type described in the adopted building/fire code.


Greg Kessinger, SET, CFPS, president of an alarm installing company since 1981, teaches NICET training classes to fire alarm system designers and installers and continuing education seminars for Ohio’s fire alarm inspectors. You can reach him at 888-910-2272; e-mail: [email protected]; or visit his website at