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
I have a question, we are in San Antonio , TX and are building garden style apartments. In a perfect world all of our system sensors would match because they would be available . However because of the pandemic we are unable to get the system sensor horns and have had to find alternatives. That being said we have now had to substitute low frequency horns of a different brand ( Kidda) into the building. We have had to put the new horns in the units and the sensor system horns in the breezeways. I am now being told by our fire department that the horns have to be in sync because of epilepsy . I am not finding info on this.
Other jurisdictions do not have this same requirement in the same state. ( for example Dallas, Houston and Austin. )
I would love to talk to someone about this if at all possible xxx-xxx-xxxx.
Hi Erin,
NFPA 72 Chapter 18.4.2.3 requires the standard evacuation signal (temporal 3 pattern) to be synchronized within a notification zone. In your case, a zone would be the devices in the breezeway. Each apartment would also be a zone. If you have multiple sounders in an apartment, those would need to be synchronized together, but not necessarily with the breezeway sounders.
Epileptic seizure concerns come from the ‘disco effect’ of non-synchronized strobe lights, not sound. The synchronization of audible patterns allows for clarity of signal and wouldn’t trigger an epileptic seizure, but non-synched audible patterns create an echo effect that can be disorienting. I’ve heard the effect and it is surprisingly disorienting. So while the specific reason cited for audible synchronization may have been mistaken, the intent is the same and required by NFPA 72.
If you put different manufacturers on the same fire alarm notification circuit, you lose the synchronization. So if your apartment sounders are on the same circuit as the breezeway sounders, nothing will synch if you mix manufacturers. Fire alarm panels can only be programmed to use a single synching protocol so you can’t synch per circuit if they all come from the fire panel. However, if the apartment sounders are strung together on a separate circuit than the breezeway sounders, you may have options. If that’s the case:
• You could have the fire panel re-programmed to provide no synch protocol and install brand specific synching modules that the circuits pass through on their way out. You would put one brand in the units and a different one in the breezeway. All devices on a single circuit have to match.
• The apartment sounder circuit(s) could be swung over to a separate power supply that could be installed to synch one brand and the fire panel would synch a different brand in the breezeway.
• If none of your apartments have more than one sounder, they don’t have to synch so you could mix manufacturers if, again, they are on a different circuit than the breezeway sounders.
• Bottom line: The breezeway sounders have to be synchronized and the sounders in any apartment with more than one sounder have to be synched. Individual apartments don’t have to be synched with other apartments or the breezeway. All notification devices on a single circuit have to be from the same manufacturer in order to have their signals synchronized.
I know that doesn’t help you with the problem of product availability, but FWIW, System Sensor just announced last month that they were bringing back the previous model of low frequency sounders due to supply chain demands. They’re available by special order so you may want to contact your local ADI distributor to see if they can be ordered & received in a timely manner. The models are HR(W)-LF for the red (white), wall mounted sounder and P2R(W)H-LF for the red (white) wall mounted sounder/strobe.
I hope that answers you question adequately. Let me know if you have any other questions or need more information on scalable, versatile Gamewell-FCI fire alarm systems that use System Sensor and other brands’ notification devices
Gene Rowe, SET
NICET Level IV, Fire Alarm Systems
Affiliated Fire Systems, Inc.
Downers Grove, IL
I hope you are doing well,My question is about any code section that requires audio synchronization of the notification circuits in R-2 or any other occupancy group.As you know there are mix low frequency and horn appliances in the close area that are heard at the same time.is there a code section similar to the visual sync requirement, please let me know.I appreciate your response.
RespectfullyHamid HashemiSecurity Engineers Inc.
M: 510-760-0100T: 925-478-5707
Hi Hamid,
Yes there is. NFPA 72 Chapter 18.4 addresses audio characteristics and Chapter 18.4.2.3 specifically states “The standard evacuation signal shall be synchronized within a notification zone.” Notification zones are generally floors, but atriums are also considered a zone so circuiting or synchronizing that area needs special attention. If you’re using low frequency sounders or sounder smoke detector bases in apartments, synching their output to the corridor horn/strobes will require the sounders to be connected to a NAC circuit that has the same synch pulse as the corridor devices. The same synch pulse that synchronizes the strobes will synchronize the horns & sounders. Of course, you have to ensure all the audio devices are set to the same 3 pulse temporal pattern as well. Check out Gamewell’s data sheet on low frequency sounder bases. I hope that answered you question adequately. Feel free to contact me if you have any questions or need additional information.
Gene Rowe
Gamewell-FCI by Honeywell
Affiliated Fire Systems
Downers Grove, IL