The contractor's role in complying with intelligibility and audibility requirements
NFPA Journal®, July/August 2010
The 2010 edition of NFPA 72®, National Fire Alarm and Signaling Code® , places the responsibility for complying with the intelligibility and audibility requirements squarely on the designer. Section 22.214.171.124.2.1 states:
The following requirements shall be met for layout and design:
(1) The speaker layout of the system shall be designed to ensure intelligibility and audibility.
(2) Intelligibility shall first be determined by ensuring that all areas in the building have the required level of audibility.
(3) The design shall incorporate speaker placement to provide intelligibility.
Recently, a contractor asked me who had to ensure that the engineers who designed a fire alarm system had done their job. I responded that both the installing contractor and the authority having jurisdiction (AHJ) had that responsibility. Although the contractor agreed that the AHJ had responsibility, he felt that a contractor should have none.
"All I have to do," she insisted, "is simply install what the engineers’ design mandates."
I strongly disagree. The contractor must understand the code requirements and ensure that what he or she installs satisfies those requirements. In fact, the contractor partners with the engineers to check their design.
If you did not create the design and your installation follows contract plans and specifications, the actual liability and responsibility does rest on the engineers. Yet we all remember when we did something wrong and gave the excuse, "Billy told me to do it!" Typically, our parents would answer, "If Billy told you to jump off a bridge, would you?" Sheepishly, we would answer, "No." That same principle applies here. Regardless of where the liability rests, a contractor should make certain that what he or she installs meets the requirements of the code.
Most fire alarm contractors have little sound and communications experience or training, so they won’t know that every new system still needs to be balanced and possibly equalized. Say, for example, that the engineers specify that the installer tap all speakers at a quarter watt.
Then, during the acceptance test, they might discover that the acoustics of the space require an increase in that setting. The engineers did not create a bad design. Rather, the required testing simply disclosed a needed correction because of finished field conditions. The engineers would expect that might happen in the normal course of an installation.
But if the engineers didn’t tell the contractor what tap to use initially, that should alert the contractor that issues may arise that will require adjustment. Or it might alert the contractor that the engineers expect the contractor to choose the proper tap.
A contractor who discovers information missing from the drawings should submit a request for information to the design engineers. To do this, the contractor must become familiar with the fundamentals of sound reproduction and communications design.
The same holds true for the AHJ, who is the first competent review person to see the engineers’ design. The AHJ should have enough training and knowledge of the code to hold the engineers accountable for compliance during the design review and permit stages.
If a requirement exists and the engineer fails to follow it, the AHJ fails to discover that failure, and the contractor perpetuates that failure, the legal system will ultimately have to sort out the resulting mess to protect the rights of the owner and the occupants of the building. If everyone in the chain, from design through installation, accepts his or her responsibility, however, we can expect more reliable emergency communications systems. There is certainly enough responsibility to go around.
Wayne D. Moore, P.E., FSFPE, is a principal with Hughes Associates and immediate past chair of the NFPA 72 Technical Correlating Committee.