How to Design a Fire Alarm System – Easy tips

After 8 years in the fire alarm design field, I decided I will go ahead and post a “how to” for the people just starting out in fire alarm design. I hope you understand that what I am posting below is not trying to suggest or imply that every jurisdiction goes by the same standards. Some have higher standards than others so some of what is posted below, may not be acceptable in their jurisdiction.
The specific details and codes of fire alarm design can vary by Jurisdiction. While the initial design is the same by default. The phrase you need to always remember when designing a fire alarm system is “can the initiating devices detect problems and can all notification be heard and seen?”.
Remember; if you don’t know. Then call the AHJ (authority having jurisdiction)

Be sure and watch the video below to see in action what I am talking about here. Sorry I don’t talk in the video. so.. may as well turn on the radio.

Proper visual coverage

Candela Coverage
picture C

Visual notification devices typically have adjustable candela settings  so that you can buy a bulk of one device and place them throughout a building or unit, and change the candela setting to match your needs. Some special needs devices are required for certain areas though.
In picture C the hallway length is 26 feet, and the coverage of a 30 candela is 15 feet in either direction, the 30 candela selection was the optimal choice. The tool (square with the X in it) you see measuring the array is something I made a few years back and turned into a block and call it up on many drawings. I have one for all typical candela settings , 15cd, 30cd, 75cd, and 110cd. I also have another that has all 4 in it so I don’t have to keep switching between them all when I am looking for a proper fit. I suggest that if you make one, add it to your template. If you don’t have a fire alarm template I have a couple for sale. Just click anywhere on this page that says “fire alarm template ” .
When you make your block, be sure and make it as useful as you can by adding as much information as you typically need, into the block to use later. because you will use it all every time if you use it one time. I’ve added candela selection and voltage to my notifications. Saves so much time. and I don’t have to remember so much while I work.

Simply stated
Audio  and visual notification for the hallways and corridors and visual notification for the rooms connected to the hallway.

Two doors deep and every other.

picture A
picture A

This is an audio notification coverage trick. Which suggests that you do not let the audio coverage exceed one door with in a unit/building. Meaning if the main corridor of a building has horn strobes or speakers in it and you are working on a unit that has a main entree with doors that lead into hallways with multiple rooms/offices, (picture A For this one we will use horn strobes) Note the location of the audio notification in the corridor and consider if the nearest horn strobe is within audible range of the main entree area. In the case of the picture below (picture A) we will say that the horn strobe can be heard in the Reception area of the suite/area of work. In this case a strobe for visual notification would be the first object placed in the reception area.

picture B
picture B

However, since the unit we are working on may be getting built out at a later time than the original installation we will design this independently from the rest of the building. Making the main entree area the starting point of our notification coverage (see picture B). Since the reception area in theory would hold multiple people in it and it’s ambient decibel could be quite high, we will make this the first point of audio notification. We will add a horn strobe to this room.Now we exit that room into the unit’s hallway and the first device will typically be a visual notification device so we will place a strobe in this area. It would be good practice to make the next notification device from the first strobe a horn strobe to maintain audibility throughout the unit. Do your best to maintain that pattern. When you come to a point where you you have to question audibility (due to turns in hallways or rooms within rooms), Go ahead and increase audibility by adding another horn strobe even if it breaks your pattern. As depicted in picture B , there isn’t an immediate horn strobe in the hallway from the conference room, and there will in theory be more than one person in that room when occupied, proper audible notification would be to add a horn strobe in that area.

Smoke detection
Smoke detectors have an area of coverage of about about 15 feet to the left, 15 feet to the right. Again I advise you make a block for this measurement also. and save it to your fire alarm template for later use. 30×30.
In most jurisdictions, smoke detectors might not be required in every room of a commercial building if the building has a full fire sprinkler system installed.
This means smoke detectors likely are required through the hallways and corridors, but not necessary in offices and lobby. No sense in “Over Smoking” a building.
It is best to call your AHJ and find out their requirements.

Pull stations
Pull stations at every exit and every stair well, within 5 feet of the door, unless not required by AHJ.

Battery Calculations and Voltage Drops
Important part of your design. Tells if you have designed with the optimal amount of booster panels to correctly power your notification devices, and if the battery will last long enough to withstand the required time of holding charge in the event of power failure. Most of your vendors have excel spreadsheets that help you do this work. I have my own. Mine makes it faster and easier for me. I guess since I made them myself. I recommend you make yours too and base them on exact details of requirements.


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