Your questions answered: Fire detection and notification
Fire detection and notification systems are complex for fire protection engineers to design. The presenters from the Aug. 27 webcast offer additional guidance.
Fire detection systems—including fire, smoke, heat, linear, and intelligent—are required at varying levels in nonresidential buildings. Based on the building type, the occupants, and codes and standards, fire protection engineers must know which products and systems will best support the owner’s needs and authority having jurisdiction’s (AHJ) requirements.
The Aug. 27 “Fire/life safety: Detection and notification systems” webcast presenters addressed questions not covered during the live event.
Question: I often hear this: If a building has a sprinkler system, you don't need smoke detectors and vice versa. My understanding is this: If the building code requires a smoke detector system, it's required, otherwise it is optional. Can you please explain?
David Lowrey: The requirement for a fire alarm system is based on which code is adopted within the jurisdiction you are working. It is true that if you install an automatic fire sprinkler system the requirements for a fire alarm system (including the installation of smoke detectors) are no longer required by most model building and fire codes. At this time, any detection that you install is the choice of the owner. You can always go above and beyond the minimum requirements in the model codes. Once you choose to install detection, than it must be installed in accordance with NFPA 72: National Fire Alarm and Signaling Code.
Question: Please explain the required 2 hours fire protection/separation for communication/notification circuit wiring.
David Lowrey: This is requirement is only required if your communication/notification circuit is required to be “survivable.” Circuit survivability is only required when you are relocating occupants or performing a partial evacuation. Sections 23.10.2 and 24.3.6 of NFPA 72 require some type of survivability of the circuits. Section 12.4 defines the different levels of circuit survivability. Level 2 and Level 3 require the circuits be protected by a type of 2-hour protection.
Question: What areas are required to have the evacuation decibel levels be 15 dBA above ambient? Everywhere, or just certain locations?
David Lowrey: The simple answer is: Everywhere you are required to have audible notification, your audible must be 15 dB above the average ambient or 5 dB above the maximum sound level for 60 seconds, whichever is greater (public notification). However, maybe the question is, where do I have to provide audible notification? That answer lies within the adopted building and fire code, which will state when and where audible notification is required. Most of the building and fire codes as well as Section 126.96.36.199.2 of NFPA 72 use a more generic statement and says the occupant notification shall be provided in all “occupiable” areas. This can and does become a debatable topic among fire alarm designers, building owners, and authorities having jurisdiction (AHJs) on the space being occupied on a regular basis as defined in NFPA 72 Section 3.3.178. If the space is determined that is occupiable and is occupied on a regular basis, than you must meet the sound pressure levels as stated in NFPA 72 Section 18.4.3 (public mode) or 18.4.4 (private mode).
Question: Is a mass notification system now required by NFPA 72?
Raymond Grill: NFPA 72 does not require the installation of a mass notification system. It provides design and installation criteria when one is required by an owner or some other code or by specification.
Question: Where or how do I find what code applies?
Raymond Grill: The starting point is to understand what jurisdiction the project is located in and who will serve as the AHJ. You would then want to contact the AHJ to identify which codes are applicable in that jurisdiction. Most building and fire departments have websites that are good starting points where they publish the codes that are in force in the jurisdiction. You would also want to find out whether there are any insurance carrier criteria that may be applicable. This information should be provided by the owner.
Question: We find that elevators are some of the most difficult to design for due to the number of codes that must be met. NFPA 70, NFPA 72, ANSI 17.1, etc. Do you have any comments about how designers can meet all of these codes?
Raymond Grill: NFPA 72 has provided all of the fire alarm design criteria applicable to elevators in Chapter 21. If you are designing the electrical and other engineering aspects for elevators, you do need to be familiar with the editions of the code that are applicable in the jurisdiction. Design for elevators can also be product-specific. Almost every project of any significance that I have worked on has included an elevator consultant to specify the elevator requirements for the project.
Question: Please clarify there is a difference between monitoring of sprinkler flow and a full fire alarm system including occupant evacuation.
Raymond Grill: Yes, there is a difference. There are instances based on occupancy where the code will require a sprinkler system and it also will require the sprinkler system to be electrically supervised by a fire alarm system. The fire alarm system is required to send signals to a supervising station, which will in turn notify first responders. A full fire alarm system including notification appliances in the building to notify the occupants is separately required in the building codes based on occupancy.