Your questions answered: Fire and life safety: Detection systems

Fire detection systems are specified for the safety of the building’s occupants in the event of a fire. Read more for responses to items left unanswered at the April 28 webcast

By Consulting-Specifying Engineer May 6, 2022
Courtesy: CFE Media

Fire and life safety systems need to be specified, installed, commissioned and maintained, depending on each building type and location. As noted in this April 28, 2022, webcast, detection systems are designed to protect the building occupants, address property protection and continuity of operation and owner requirements.

Presenters:

  • William Koffel, PE, FSFPE, President, Koffel Associates Inc., Columbia, Md.
  • David Lowrey, Chief Fire Marshal, Boulder Fire Rescue, Boulder, Colo.

How do you address frequent false alarms?

William Koffel

William Koffel

William Koffel: Proper design, proper device selection, proper installation (meeting NFPA 72: National Fire Alarm and Signaling Code requirements); proper commissioning and proper integrated test and maintenance.

Does the authority having jurisdiction have authority to make a code change?

David Lowrey: Only through the legal means set up by their jurisdiction. However, the code does allow the AHJ to make interpretations of the code and standards.

What can you tell us about gas detection systems and NFPA 72?

William Koffel: This is a broad topic. Various codes require gas detection for certain hazardous processes and operations. The codes generally provide minimal guidance with respect to the system design and installation. I would offer that NFPA 72 could be use for guidance with respect to circuit integrity, pathway performance, pathway survivability, power supplies and performance of the occupant notification system.

NFPA is in the process of developing a new standard to address fuel gas detection, if that is your concern. The overall organization of NFPA 72 was established to be able to include gas detection and that was specifically discussed at a recent meeting of the Correlating Committee. Essentially you have initiating devices that need to provide warning to building occupants and to potentially notify emergency response personnel.

What type of fire detector sensors would work best for electrical rooms that contain switchgear, switchboard, panelboard, motor starters, dry type transformers (only)?

David Lowrey

David Lowrey

David Lowrey: Since it’s not a “life safety” type of environment, any of the spot or line type heat detection will work. I see no reason why a photoelectric spot type smoke detector would not work just as well, depending on your tolerance for nuisance alarms.

What are best practices for fire alarm and notification design that will ensure that personnel will evacuate a building expeditiously instead of staying at their location?

William Koffel: This may be more of an issue of emergency planning (fire wardens, for example) and proper training than system design. However, there is some evidence that people are more likely to respond to voice messages than standard evacuation tones. NFPA 72 has addressed it to some degree by establishing criteria for a standard evacuation signal so that it is distinct from other alarm signals in a building.

Are fire alarm control panel or remote annunciators required to be located near the main entrance or at the exterior of the main entrance? Can we locate FACP in electrical closets or electrical rooms? Is there a guideline or rule for where FACP are required to be located?

William Koffel: Some codes will require remote annunciation. When required, it is usually to be provided at a location approved by the AHJ. While remote annunciation is typically provided near the main entrance, it may have more to do with fire department response to the location. NFPA 72 contains some requirements for the protection of fire alarm control units when installed in rooms that are not normally occupied.

What is the required documentation for deferred submittal?

William Koffel: NFPA 72 contains the requirements for documentation and those requirements are independent of whether the submittal is deferred for some reason.

When will you be requiring Class A rather than Class B network topology? Rings allow more reliability in case someone disconnects a link in the middle.

William Koffel: This is a good example of working with the owner to determine their performance criteria and the risks associated with circuit integrity in the building. Some owners prefer conduit; some owners prefer Class A and some will just want the code minimum.

When you reference NFPA 72, 7.2 for documentation for plan review/permit, are all the items in 7.2.1 required by the engineer (i.e., battery calculation, system software) or is this list the complete requirements including shop drawings from the contractor?

David Lowrey: I expect them to come on the shop drawings for permit purpose.

As an electrical design engineer, I am tasked with preparing contract documents. Therefore, I typically prepare performance specifications that are not detailed, resulting in initial plan review drawings not having detail as described in Chapter 17. How much is required upfront and what can be delayed until the fire alarm installer prepares the complete submittal?

David Lowrey: That simply depends on what is required to be submitted and when. I don’t approve performance specs or contract documents. I only approve the shop drawings for permit. Other jurisdictions may do it differently.

William Koffel: Chapter 7 of NFPA 72 addresses this issue. Depending on what you mean by performance specifications, it may not ensure that contractors are bidding equivalent systems.

What do you think about the fact that design drawings represent preliminary design by an engineer while the shop drawings represent final installation by the contractor and ultimately the contractor is liable for the fire alarm? The point of this question is to discuss the disconnect in the industry regarding the liability of the fire alarm design between the engineer and contractor.

William Koffel: I would disagree that ultimately the contractor is responsible for the fire alarm system. The registered design professional, where there is one on the project, should also be liable for their portion of the work. As noted in the webcast, where a contractor accepts a project where there is not a registered design professional or where the registered design professional has not prepared adequate documentation, my non-legal opinion is that the contractor is exposing themselves to increased liability.

How do you test a fire sprinkler system or a heat detection system? You cannot know if the sprinkler works unless activated. But then the sprinkler head needs to be replaced.

William Koffel: Sprinklers themselves are very reliable and rarely fail (fail to operate when needed or operate when not needed). There are various tests performed to evaluate the adequacy of the water supply and the operation of various components of the sprinkler system, such as water flow alarm. The calculation procedure is based upon basic fluid mechanics and if the calculations are done properly (should not be an assumed situation) and the water supply is adequate based upon the adequacy determined by the calculations the sprinkler system should perform.

Other concerns are where the sprinkler system is not adequate do protect the hazard (initial design or changes). When a sprinkler system operates, they are generally about 96% effective. The biggest concern is operational reliability (does it operate) and the most common failure mode is closed valves. NFPA 72 addresses the methods to test various forms of heat detection (see Chapter 14)

If a building has a direct digital control for the HVAC system and a fire alarm system, should the fire alarm system shut down the HVAC directly to each unit with control modules or can the DDC system shut down each HVAC equipment with a contact from the fire alarm system?

William Koffel: You are asking a fire protection engineer, so naturally the answer is the fire alarm system should perform most of the functions. Seriously, NFPA 72 addresses the performance requirements for the fire alarm system. What are the performance requirements for the building management system, security system or other systems being controlled. When the other system is used, the control module or relay should be within 3 feet of the control equipment to address the circuit performance requirements up to the control module/relay.

In the following example, if smoke or sprinkler flow shuts off HVAC, can corridor be used for return air? Example: R-2 congregate living (dorm for more than 16), Type 5B construction, fully sprinklered, one story.

William Koffel: In most jurisdictions, this would need to be addressed as an equivalency or alternative method of compliance. One concern is that using the corridor results in air movement between the corridor and adjacent spaces. Even if the system is shut down during a fire condition, the openings through which the air is being moved on a normal basis will allow for smoke spread.

Smoke detectors for use in electrically classified hazardous areas (explosion proof versus intrinsically safe): Please dwell a little as the U.S. marketplace mostly draws a blank here in comparison to the European marketplace and manufacturers.

William Koffel: In the U.S. market, smoke detectors are perceived to be more of a life safety device. That probably explains why you don’t see as much smoke detection in these spaces — although certainly permitted and possibly of value — as you do sprinkler protection and/or heat detection.

How long will an addressable fire alarm system last?

William Koffel: Today’s systems generally have an extended useful life (not sure I really have seen a study of equipment reliability over time). Today manufacturers generally make new equipment compatible forward and backward. In the past, as new technology was introduced it would require replacement of existing hardware.

How can we get design professionals more onboard with the more advanced multicriteria and multisensor spot detectors, which pose a marginal cost increase but are significantly more effective in mitigating dangerous unwanted alarms?

William Koffel: Education and properly defining the needs of the owner.

If a project is determined to not require a manual fire alarm system by code and the owner would like to put one in anyway. Do we need permission from the AHJ to install this system?

William Koffel: Absolutely. One can always go beyond code. However, if you are going to put in a manual fire alarm system, the requirements of NFPA 72 should be met so as not to create a false sense of security. There is some language in NFPA 72 that talks about non-required detection devices not needing to meet all of the requirements of NFPA 72 where the detection is for a specific purpose (the smoke detector over the server in my office, as an example).


Consulting-Specifying Engineer