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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We have a machine room-less elevator where the motor is located on top of the elevator cab and the elevator equipment is located within the elevator shaft.

NFPA 13 (2016) 8.15.5.3(2) allows sprinklers to be omitted from the hoistway of "traction elevators" where the hoistway is "protected by smoke detectors, or other automatic fire detection installed in accordance with NFPA 72", and several other requirements.

NFPA 72 (2016) 21.3.3 states that only the elevator hoistway and elevator lobby smoke detectors or other automatic fire detection (as permitted by 21.3.9) shall be used to initiate Phase I Emergency Recall Operation. 

NFPA 72 (2016) 21.3.9 states that if "ambient conditions prohibit installation of automatic smoke detection" that other automatic fire detection initiating devices shall be permitted.

What type of ambient condition in an elevator shaft would qualify as prohibiting smoke detection? 

I understand smoke detectors in elevator hoistways can cause nuisance alarms (NFPA 72 2016 A.21.3.9) and are very difficult to test and replace within elevator shafts, so in my opinion a heat detector would be better for elevator recall in the shaft if it's allowed by code.

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Does anyone have a good resource for determining audibility loss (dB loss) through various door types? I recall seeing a reference chart that was perhaps printed in a fire alarm handbook in the 90's, but I don't have a copy.

​Intelligibility is a world all on it's own - if we need intelligibility I typically locate a speaker on the opposite side of closed doors (private offices, for instance). Is there a way I can model or predict intelligibility through closed doors? I've tried Ease EVAC years ago using door gaps, but it wasn't well suited to model the losses at that time.

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I work for an engineering consultant and we often do work directly with university and healthcare clients that expect an estimate as part of the deliverable package.

I typically track square footage costs whenever I receive them (on past projects), but even that is rare. I've since transitioned to using RS Means unit cost pricing and adjusting for location and historical cost increases.

For others doing cost estimation, have you found relative accuracy using RS Means? Are there other estimating providers that are better suited for cost estimating in our industry?

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Other than the Contractor's Material and Test Certificate for Aboveground Piping (NFPA 13) and System Record of Completion (NFPA 72), where can I find a good procedures for acceptance testing for fire sprinkler and fire alarm systems?

​Is there a step by step approach that I can add to for my particular project?

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A middle school is being expanded by two classrooms and about six small offices and supports spaces. The addition is separated by a fire barrier from the main school, and the existing school has a temporal-3 horn/strobe fire alarm system throughout (and is fully-sprinklered).

Current code requires an emergency voice/alarm communication system for the expansion, which the design team intends to provide.

The question is how to address the interaction between the new voice system and the existing? Is this purely and AHJ call?

Ideally, the school should consider upgrading their entire fire alarm system to voice for a cohesive message and best benefit. However, funding is very tight and we're not confident they'll have the support they need to do a full upgrade at this time.

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We occasionally have inadvertent fire alarm activations that we can't get to stop until a fire alarm company arrives to correct the issue at the facility where I work. Are we permitted to turn off the alarm and conduct a fire watch during this time instead?

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Can a municipal property - such as a fire station in this instance - have it's fire alarm system directly monitored by their own call dispatch center?

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For those who regularly bid and/or review "performance-specification" or "delegated-design" drawings, what important pieces of information are often left out?

In other words, what should engineers always include for you to price or review a job effectively that you often don't get?

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