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.
By Raymond Grill, Arup; David Lowrey, Boulder, Colo., Fire Rescue September 1, 2015

David Lowrey (left) and Raymond Grill (right) present additional information about 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 18.4.1.4.2 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.

Question: Does the fire alarm system effective and need to be designed for road or rail tunnel system?

Raymond Grill: The design of fire detection for road and rail tunnels does have to take into consideration the challenging environment within the tunnels. There are numerous different factors that may need to be considered and each application may be unique. Factors such as smoke control, suppression (whether it is provided at all and whether it is automatic or manual), emergency egress arrangement, etc. can impact the type of detection and factors such as notification and emergency communications. A risk analysis and plan taking into consideration the emergency plans for dealing with a tunnel emergency also need to be considered.

Question: What is the dividing line between when a fire alarm system controls HVAC equipment versus when a building automation system is allowed to control that same equipment during a fire event? Example: unit shutdown, damper closing, etc. Where is this delineated?

Raymond Grill: This is a designers/owners choice. If the building automation equipment is going to be performing smoke control functions, it is required to be UL listed in the UUKL category. Fan shutdown as required by the mechanical codes is often done at the unit and smoke detection equipment often comes pre-installed with the air-handling units (AHUs). The decision may also be driven by how the systems are going to be maintained and operated. Having the fire alarm override and control fans in smoke control mode may facilitate testing and ongoing maintenance of a smoke control system.

Question: What is a toxic gas? Isn’t all smoke toxic?

David Lowrey: Yes, all smoke is a form of toxic gas. 

Raymond Grill: Toxic gases in the context of the presentation was intended to mean toxic as defined by the building and fire codes for determination of “H” hazardous occupancies. While all smoke is toxic, we don’t have smoke in a building on a regular basis.

Question: NFPA 101-2012, Section 9.6.3.5: Is it the intent of 9.6.3.5 to require visual notification throughout a building, including all private employee work areas (e.g. private offices)?

Raymond Grill: See sections 9.6.3.5.1, 9.6.3.5.2, 9.6.3.5.3, 9.6.3.5.4, 9.6.3.5.5, 9.6.3.5.6, and 9.6.3.5.7, 9.6.3.5.8. These sections provide additional guidance and exceptions to where visible notification appliances are required. The Americans with Disabilities Act (ADA) generally requires visible notification appliances in public and common use areas. Various local jurisdictions may also have specific criteria.

Question: What is your opinion of prescriptive fire alarm design versus performance design?

Raymond Grill: Performance based design has its place. It is typically used when the facility or hazard does not allow for a design that complies with the prescriptive requirements of NFPA 72. This may be related to initiating device placement or notification appliance placement. It can be used to optimize a design, but due to the additional effort and time required for review and negotiation with the authorities, it is difficult to justify pursuing.

Question: What is the difference between a fire area and a compartment?

David Lowrey: A fire area is defined within the model building codes, as the floor area enclosed by fire-rated construction. This is either by vertical fire-rated construction, like fire walls or exterior walls and/or by horizontal fire rated assembly. A compartment does not necessarily have to be enclosed by fire-rated construction or assembled to meet any nationally listed criteria. A compartment is typically enclosed on all sides, which would contain the smoke and heat long enough to activate detection but not necessarily contain the actual fire from movement. Although a “fire area” may be a compartment and a compartment may be constructed with fire resistant or rated material, most of the time a compartment is a room or other similar smaller space.

Question: What is the status of 2-hour fire rated (CI) cable approvals?

Raymond Grill: This link will take you to the UL update on Fire-Resistive and Circuit Integrity Cable. Most of the listed assemblies require physical protection to achieve the fire rating. The NFPA 72-2016 has some circuit arrangement options to meet survivability requirements.

Question: The local AHJ does not want the fire alarm to shut down elevators if sprinklers are in an elevator shaft. Should we still design it in each time and let the AHJ comment?

David Lowrey: You must design the system per the adopted design standard (NFPA 72) considering any local amendments to that adopted standard. You must also meet the requirements for any other adopted code(s) that have specific requirements for elevators (building code and AMSE A17.1). Let the local AHJ red-line or write comments on how they are requiring this to be designed and installed. You could also ask them to put their design requirements in writing for all fire alarm design within their jurisdiction and design off those requirements. You need it documented on why you did not design or install the system in accordance with national recognized codes and standards. 

Question: Would a local water bell qualify as monitoring?

David Lowrey: No.