Crash Course Fire alarm – Signaling devices

Introduction

 

Your boss puts you on an fire alarm design job, but your knowledge is limited to your smoke detector at home? Is it true that a pull station contains an inkjet to incriminate you if you pull it for no other reason than to shorten your Friday? These are the questions I will try to help you with in this series of posts on building fire alarm systems.

 

These posts are intended, but not limited to:

 

  • Electrical engineers from consulting engineering firms
  • Subcontractors at fire alarm companies
  • Junior engineers who have no idea what it is (trust me, i’ve been there once!)

 

The fire alarm scope is the responsibility of the electrical engineer. The fire alarm system is not intended to suppress the fire, but rather to detect the fire, facilitate the evacuation of personnel and alert the fire department.

I will introduce today the signaling devices that are part of fire alarm system.


1- Standards in force

Code de Construction du Québec

 

For current articles of the Quebec Construction Code, please refer to:

 

  • Warning Signals and Warning Signs (CCQ Article 3.2.4.17)
  • Audibility of Signals (CCQ Article 3.2.4.18)
  • Phonic communication network (CCQ Article 3.2.4.21)

 

Please note that while Quebec has its own Construction Code, you should also learn from the american National Fire Protection Agency or NFPA as an additional reference.


2- Non phonic signaling

 

Non-phonic communication is any form of auditory signal that is not verbal communication. For example, bells, horns, mini horns, sirens and bullhorns are examples.

 

A) Bell

Fire alarm bell

 

Bells are available in different sizes, motorized or vibrating. The sound produced is both powerful and metallic. Ideal for spaces occupied by many people. NFPA 72 requires that a non phonic signal be at least 15dB above ambient noise. Since the offices have an ambient noise of 50 to 60dB, the bells resonate at a power of 65 to 75dB! Colored with firefighter red, it is forbidden to paint them. The power supply is 120V AC, but can be 24V DC or even 6V DC.

Trustworthy manufacturer: Kidde

 

B) Horn

Fire alarm horn

 

The horn produces a deep, piercing sound that is easily distinguishable. The case is made of sturdy and flame retardant plastic in red or white color. The advantage of the horn over the bell is that it is possible to transmit a signal continuously or a signal punctuated with pauses.

For example, rather than having a beeeeeeeep, it is possible to have beep … beep … beep … pause … beep … beep … beep … pause, etc. Finally, it is possible to adjust the frequency of the horn to have an high pitch or a low pitch sound. Ideal for different scenarios of evacuation or relocation of staff according to the functionality of the building.

 

C) Mini horn

Fire alarm mini horn

 

Designed primarily for homes and condominiums, the mini horn is more discreet and less noisy. Molded in a sturdy plastic case, it can be red or white in color. It is possible to obtain it with an integrated silence function.

 

D) Bullhorn siren

Fire alarm bullhorn siren

Not exactly like your hand held bullhorn, but close. The bullhorn siren is able to transmit the voice, but with a lot of distortion and garble. It is also capable of producing an extremely high decibel sound. The sound is close to the warnings sirens used during the Second World War to warn citizens of incoming bombing raids. Today, they are found on sawmill yards, boats and in some factories.


3- Phonic Signaling – Speakers

 

Fire alarm speaker

 

The speakers allow the integrated broadcast of understandable emergency voice messages, warning and alarm signals. These are very discreet and blend well with the ceiling tiles. Ideal for office environments. The power is adjustable on site by the building maintenance team. Equipped with a steel case, round or square, they are usually white. However, it is forbidden to paint them under penalty of losing the certification.


4- Visual Signaling – Strobe

Fire alarm strobe

 

Visual signaling is used to alert people with hearing impairments or when the noise level is too high and workers are known to wear hearing protection. Ideal in the factory. Molded in a sturdy and flame retardant plastic case, it is usually red or white in color. There are also suspended ceiling models like this one.

Fire alarm ceiling strobe

The set of strobes requires the use of a synchronization module if it is desired that the strobes all flash at the same time.


5- Combined sound and visual signaling

 

As its name would suggest, sound and visual signaling combines both. Thus, there is the bell strobe,

Fire alarm bell strobe

 

the horn strobe

Fire alarm horn strobe

 

and the speaker strobe.

Fire alarm speaker strobe

 

With the advent of light-emitting diodes or LEDs, combined sound and visual signaling is replacing purely visual or sound systems. With the very low cost of LEDs, many residential, commercial and industrial property owners opt for the combined option for reasons of diligence towards the hearing impaired or for security reasons.

In hotels for example, thanks to the Internet of Things and the lower costs of LEDs, it is perfectly possible to have a set of visual and auditory signaling that flashes sequentially to indicate the flow of evacuation, such as the signaling on airport tarmac and runways.


6- Firefighter phone

Firefighter phone

 

As a kid, who hasn’t worn a firefighter hat while pretending to take emergency phone calls! The firefighter phone allows firefighters to communicate with the operator of the main fire alarm panel when they are on the different building floors. Thus, next to each manual pull station near an emergency exit is a firefighter phone.

The two-way communication request is made when the handset of a floor telephone is off-hook. The firefighter at the main fire panel charge at the station is then notified by visual and sound signals and can then connect to that circuit.


Conclusion

 

The fire alarm is a vast subject for which the electrical engineer is responsible. You learned today which articles were in force concerning signaling and where to look for them in the Quebec Construction Code. You’ve also learned about bells, horns, bullhorn sirens, speakers, strobes, combined signaling, and firefighter phones.

The next post will focus on the main fire alarm panel.

2 Replies to “Crash Course Fire alarm – Signaling devices”

Leave a Reply

Your email address will not be published. Required fields are marked *