Do fire alarm strobes always have to be synchronized?

I was recently asked a question about whether two strobes had to be synchronized if they were the only two in a field of view .  The facility’s fire alarm vendor told him that if a field of vision had just two strobes in it, they did not need to be synchronized.  When he tried to verify that claim, he felt the visual section of Chapter 18 wasn’t clear on the subject.

I replied that the installer is technically correct in that, since 1996, all manufacturers’ strobe flash rates were lowered so that viewing two non-synchronized strobes would not produce an overall flash rate considered to be dangerous. As far as code requirements, the NFPA requirement for strobe synchronization is actually found in Chapter 18.5.4.3.2 (for rooms) and 18.5.4.4.5 & 7 (corridors). If this question is being asked for a room, then the intent is to achieve a minimum light output. If achieving that output requires ‘…more than 2 visual appliances…’, then they must be synchronized. In a corridor, “when more than 2 visible notification devices are in any field of view, they shall flash in synchronization.” So technically, if just two strobes are in the overall field of view (including non-direct viewing), they don’t need to be synchronized to meet NFPA 72 requirements.

That’s in a vacuum. However, in the real world, these devices are generally on circuits that have additional visual devices that serve other areas where more than two devices are in the direct or non-direct field of view.  Additionally, the circuit may need be expanded in the future or the space may be reconfigured so that synchronization would be required. Another important real world consideration is the expectation of the facility’s reviewing AHJ (Fire Department, Department of Public Health, Joint Commission, etc.). Unless the strobes were installed prior to 1999, the expectation of every AHJ I’ve dealt with since that time is that every strobe in line of sight will be synchronized. If in response to a citation, the chief engineer of a facility wants to pull out the code book and cite specific code application of strobe synchronization to their reviewer, he may eventually win that battle (or not), but in doing so he may be opening the door to a more ‘letter of the code’ enforcement regarding other areas of concern.

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Gene Rowe

About Gene Rowe

Gene Rowe serves as the Director of Business Development for Affiliated Customer Service. He brings twenty three years of fire alarm and emergency voice systems experience to the table with both an operational and marketing viewpoint. A US Army veteran, NICET certified, an executive board member of the IL-AFAA and a member of the NFPA, he began his career establishing operational expertise as a technician, developed graphic skills with CAD design as a general engineer, gained a ‘big picture’ mindset by moving to project management and finally a marketing perspective directing business development efforts. By interfacing with a broad range of diverse organizations such as the AFAA, CAA, AIA, CEA and the IFIA, he combines concerns of the owner, designer of record, contractor, distributor and approving authority to bring a unique perspective to Affiliated.

An avid marathon runner, he resides in west suburban Chicago with his wife and two sons. He's served the community as a Cub Scout Leader, as well as coaching multiple levels of travel and park district basketball and baseball teams. Professionally, he serves as the Treasurer and is on the Board of Directors for the Illinois chapter of the Automatic Fire Alarm Association (IL-AFAA).

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