Special Q&A on NFPA 72, fire alarms and more

This Q&A covers fire rating, strobe placement and designated work areas

By Consulting-Specifying Engineer February 13, 2024

In this webcast about NFPA 72: National Fire Alarm and Signaling Code, the presenters did a live Q&A after the prepared presentation. Read the transcript of this webcast, and watch the on-demand event here. This transcript has been edited for length and clarity.


  • Ray Grill, PE, Principal, Ray Grill Consulting, Clifton, Virginia.
  • Chris Campbell, PE, Principal & Founder, Campbell Code Consulting, Elkridge, Maryland.

What is the required fire rating for a room that has a fire alarm panel?

Ray Grill: If we’re not required to provide survivability, there is no specific requirement for a rating of the room. If we are designing for survivability because we have a building that is doing partial evacuation or relocation, then typically that room would be required to be two hours if we have a building that has a fire-resistance rating of at least two hours. One of the reasons the one-hour survivability allowance was placed in the code is that the code in NFPA 72: National Fire Alarm and Signaling Code recognizes that there may be partial evacuation or relocation in buildings that are rated at one hour. In those cases, the equipment only has to be protected to one hour by a rating.

In which space can we use visible notification only versus combination speakers, strobes or horns?

Chris Campbell: The requirement for visible notification is going to be coming out of the building or the fire code, and typically per the International Building Code (IBC), visible notification is required in public and common use areas. If you are talking about a public or common use area, you are going to have to have visible notification in those spaces. Audible notification is generally required throughout the building and that is for both audibility and intelligibility. That does not necessarily mean that you must have a notification appliance in every single room or space. It just means that you need to provide the required audibility level and some form of intelligibility in each space.

Is there a maximum ceiling height for ceiling-mounted strobes?

Ray Grill: For a ceiling-mounted strobe, the prescriptive tables only go up to a 30-foot height. Now that is not the ceiling height. That is the location of the lens. If you have a 60-foot-high ceiling for instance, and you can place that strobe at a 30-foot height above the floor, you can use the tables for placement. If you need to place that strobe at a higher elevation, then you must use the performance approach and you would have to calculate or use a manufacturer’s calculator to identify how much candela must be. You would need to understand how much the rating of the strobe needs to be increased if you are going to place it at a higher elevation, but the code does allow placement at a higher elevation if you increase the candela rating to produce the same effective candela on the surfaces that you are protecting.

What differentiates public and common use from employee work areas? This refers to a break room or something like that.

Chris Campbell: An employee work area is going to be an area that is only used by employees for their work, whereas a public or a common use area is going to be something that is available to folks outside of that. That would also include things like circulation space, lobbies, waiting rooms, things of that nature. The code does have an exception. This is in the building code that employee work areas can initially not be provided with visible notification if the circuits are designed with a spare capacity that if someone needs to be accommodated with visible notification appliances that it can be added later.