Should return air duct smoke detectors associated with a fan system close only the associated damper and shutdown the fan or close all dampers on the system (including supply return spill and outside air)?

How should outside air and spill air fire smoke dampers be controlled? Should these to be controlled by fire alarm?

Thanks in advance.

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I'm working within a campus environment, and costs are something that always arise at some point during ITM conversations.

Does anyone have a great resource or tool to help to estimate a ballpark cost of ITM over a life of the building?

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I’m confused by the field of view intent of NFPA 72 for synchronization.

Do two adjacent rooms with a door between them each with strobe coverage require synchronization?

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Question for AHJs and inspectors:

Do you occasionally see fire alarm strobes mounted on the ceiling that appear to be for a wall-mounted orientation (e.g. they are rectangular and have the word "FIRE" on the side)?

I know some of these are actually for ceiling mounted applications but I've run across some that are wall-mounted only. I think the Wheelock brand might be an example? Stuff like this is hard to tell in the field for an existing building (with no documented cut sheets for what was submitted).

Anyone have tips or tricks for this?

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What constitutes a "drop" on a fire alarm Class A circuit?

NFPA 72 12.3.8.1 (2016 Edition): 
"The outgoing and return circuit conductors shall be permitted in the same cable assembly, enclosure, or raceway only under the following conditions:
(1) For a distance not to exceed 10 feet where the outgoing and return conductors enter or exit the initiating device, notification appliance, or control unit enclosures.
(2) Single drops installed in the raceway to individual devices or appliances.
(3) In a single room not exceeding 1000 sq ft in area, a drop installed in the raceway to multiple devices or appliances that does not include any emergency control function devices."

For this project in question an appliance is located approximately 12 feet away from a device. The circuit runs from the device, out 12 feet horizontally, down a wall a few feet, then back up and back to the first device. 

In my opinion, the outgoing and return circuit exceeds 10 feet so it would not qualify as Class A wiring. However, the contractor is calling this a "single drop" to an individual appliance, so he feels it qualifies as exception (2) above.

Is this considered a single drop if it's only serving an individual appliance?

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Our common CRAC Units (Cooling, Refrigeration and A/C) for data centers only cool the air directly from the data center and back into the data center.

Do these need to be shutdown with the use of a total-flooding clean agent system? 

If the CRAC unit is only exchanging air within the same space then I'm not sure what harm it would do if it's running during or after clean agent discharge. I'm curious if I'm off the mark here, thanks!

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When an elevator does not have an elevator machine room, where should the fire alarm relays for the elevator be located?

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Are there special requirements for fire alarm strobes on the exterior parts of the building (courtyards, etc)? Thinking that direct sunlight may interfere with the strobe.

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I do inspections for fire alarm systems. It's not something that is brought up often and is generally not an issue, but I am trying to educate myself on what the correct procedure is to determine the conduit size for fire alarm.

Could someone point me in the right direction? Thanks in advance.

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Solution | Posted 10/18/19

NFPA 72 states that audibility from a fire alarm system is required to be provided throughout a building. Most jurisdictions are less concerned with attaining audibility in small, non-normally-occupied rooms such as janitor closets, small electrical rooms, or small mechanical rooms. However, several military reviews have pointed to exactly these rooms and asked how audibility is going to be achieved. 

I typically provide speakers just outside of these groups of rooms such that there should be an achieved audible level, but how could I prove that during the design phase?

Is there any calculation for audible loss through a door or software that could model this loss?

I feel like there's a good handful of variables that play into whether audibility is achieved in these small rooms that may be difficult to predict.

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Solution | Posted 09/13/19

A dormitory has residential rooms which house two students. There is a traditional sleeping area approximately 12 ft x 12 ft, and a hallway with a bathroom and closet in-between the sleeping area and the main corridor.

Separating the sleeping area and the unit hallway is an opening about the size of a door opening (but with no door). This project is still in design.

How shallow would the header on this opening need to be (distance from the ceiling), in order to avoid requiring a smoke detector in the sleeping area and the hallway?

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I'm considering testing for NICET fire alarm certification. What I don't yet know and would be very interested in is who typically prepares fire alarm shop drawings? 

Do freelance fire alarm designers/engineers make up a large portion of shop drawing preparation, or is it mostly all completed by a fire alarm company's designer? Do large manufacturers (Simplex/JCI) complete all of their own shop drawing work with in-house designers?

Thanks in advance - I'm trying to get a better perspective for my career.

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Solution | Posted 08/06/19

Solution | Posted 07/31/19

Solution | Posted 07/19/19

A forensic investigator is trying to determine approximate timing of events after a fire within a hospital basement. A quick response sprinkler (RTI of 50 m^1/2s^1/2), Ordinary Temperature (65 deg C) was within a room (2.1 m high ceiling) that has an initial temperature of 73 deg F and was exposed to a ceiling plume at 205 deg F traveling at 1.3 m/s. Approximately how long should it have taken the sprinkler to activate?
     a. 2 s
     b. 16 s
     c. 33 s
     d. 38 s

Solution | Posted 07/16/19

What governs the minimum conduit size for fire alarm circuitry?

Is it just based on the ampacity factors in the National Electrical Code similar to any power circuits, or is there some other section I should be referencing from NFPA 72 or the NEC? Any help is greatly appreciated.

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Solution | Posted 07/01/19

Do you often come across AHJs who require manual pull stations at every exit, regardless of the occupancy and regardless of whether they're allowed to be omitted based on a fully-sprinklered building? 

I've come across it a few times and we certainly see some ordinances written in - I'm just curious if it's something you have seen and whether you choose to fight it or just include the pull stations.

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A forensic study is being prepared using a fire model to attempt to verify whether arson could be a cause. If the fire's origin room ceiling ceiling (3.3 m) has an initial temperature of approximately 22 deg C and is exposed to a plume along the ceiling at approximately 85 deg C traveling around 1.2 m/s, what is the activation time (in seconds) for a quick response (RTI of 40), Ordinary Temperature (75 deg C) sprinkler?
     a. 61 s
     b. 67 s
     c. 210 s
     d. 230 s

Solution | Posted 06/24/19

Someone had asked about life safety Revit families and any recommendations. We do fire alarm design and are increasingly seeing BIM become the standard when working with architects.

Does anyone have any recommendations on where to find quality fire alarm Revit families? We're not manufacturer-specific design but are looking to improve our older basic devices.

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I've taken technical writing courses and have experience working with MasterSpec, US Military specifications, vendor specifications, and various ownership standard specifications.

I'm giving an internal training to our younger staff and I'm particularly interested in opinions from contractors and vendors who regularly read a variety of specifications for bidding.

What advice would you give for those who write specifications? I'd be interested in helping train our staff as well as improve myself.

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We have a project where a control module is connected to the mechanical controls that is programmed to the variable frequency drive for a fan on a large unit. When a duct detector senses smoke, the control module (which is normally-open circuit) will close the circuit, sending a signal to the mechanical controls which shuts down the unit.

On this project we had a bad set of control modules that didn't work. We discovered this in testing with the local jurisdiction, and swapped out the modules and the system now works correctly. 

Both the jurisdiction and I wondered whether this normally-open arrangement is acceptable. If a control module were to fail, the duct detector would not be able to close the circuit on the module and the fan would remain running. In this scenario, there would be no supervision or way to know that the control module failed other than someone standing at the fan or finding the issue during testing.

My inclination is that in the future these modules could be normally-closed and open upon duct detection. That way if the module fails and opens on its own, the unit will shutdown in a "failure" mode.

Is it code required that this arrangement be fail-safe?

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