OVERVIEW 

Unlike sprinkler systems, which act to suppress a fire, a fire alarm system serves to detect the fire and evacuate the premises.  Automatic devices, such as smoke and heat detectors, sense the fire and in turn trigger audio-visual devices.  These audio-visual devices, such as horns, speakers, and strobes, act to notify the occupants of a building of an emergency situation.  Manual pull stations also activate the audio-visuals, but rely on a person to operate them.  

COMPONENTS

A fire alarm system is typically composed of a number of components.  The control panel, which is the brains of the system, processes the inputs from the field devices such as the smoke detectors, and triggers the audio-visual units when it has determined that an alarm condition is warranted.  There is a standby power supply, which consists of a battery charger and a set of batteries, that is sized specifically for each particular panel’s current load.  If the building power were out, the batteries would keep the system operational for a predetermined amount of time.  An annunciator panel, that is located in the front lobby of the building, tells emergency personnel exactly what type of alarm and where it has occurred (ie-3rd floor west wing smoke detector).  There are silence and reset switches here as well that give operators control over the system.  Lastly, a series of field devices that make up the initiating zones (smokes, heats, pulls, etc.), and notification appliances (horns, speakers, strobes), for the system.   

ADDRESSABLE vs CONVENTIONAL 

Fire alarm systems generally fall into one of two categories; addressable and conventional.  Addressable systems, also known as intelligent systems, enable each and every initiating device (smokes, heats, pulls, etc.), to have an individual address, or zone identifier.  This is most beneficial for servicing the system.  If a detector is faulty, the technician knows exactly which device is at fault.  Other benefits include less cabling for the installer.  The addressable devices all connect to a single loop that runs through the premises.  Different types of devices can hang on the same loop. 

Conventional systems are set with a certain number of zones that are hardwired to the control panel or zone expander.  Smoke detectors must be run on a separate zone from pull stations, etc.  There may be a dozen detectors on a single zone and if one is faulty, the technician is tasked with finding which one.  More cable is required because instead of having multiple device types wired to the same loop, a separate cable run for each type of device is required for these conventional systems.  

It stands to reason that addressable systems have a higher equipment cost but save on labor.  A small facility, or one with a limited number of devices, may do very well with a conventional system.  One is not better at detecting a fire than the other, they just utilize different technologies.  There are hybrid systems as well, that mix conventional hardwired zones with addressable loops on the same control panel.  They fit certain applications better than just one technology would. 

NFPA Building Codes

OSHA Fire Safety 
Information

OSHA Fire Safety Advisor
1.0a Software

Automatic Fire Alarm
Association (AFAA)

Fire Alarm Testing 
Frequency

ADA 

In recent years, the Americans with Disabilities Act (ADA), has impacted the fire alarm industry.  Minor system design changes affect the mounting height of manual pull stations, so that they are accessible to a person in a wheelchair.  Of much greater impact however, is the location of the audio-visual devices.  A hearing-impaired person certainly would be oblivious of a horn ringing.  Strobe units however, flash a tremendously bright light, some intense enough to wake a person from a sound sleep.  The ADA guidelines for locating these devices in a facility are for the horn sound level to be above ambient noise by a certain percentage, and strobe coverage to be complete.  The measures for these ratings are standardized; sound is rated in decibels and the strobe brightness is rated in candela, a measure of foot-candles. 

 NFPA

The National Fire Protection Association (NFPA), has the most impact on fire alarm system design and acceptability.  Most local Authorities Having Jurisdiction (AHJ), which inspect and sign-off on system installations, require that NFPA guidelines are met.  Although each AHJ interprets the NFPA code with their own slant, they all predominantly expect the letter of the code to be followed.  

For example, some require a UL certificate to be issued on the installation, others require a third-party inspection.  Some want duct smoke detectors to be alarm-causing while others want them to only show a trouble condition. 

 NOTIFICATION

Regarding alarm notification, the most common means is by a combination of horns and strobe units.  Certain facilities, such as high rise buildings and places of assembly (ie Churches and theaters), require speakers in place of the horns.  Speakers are part of voice evacuation systems, where a pre-recorded message is played in the event of an alarm condition.  The message informs occupants of the emergency situation and directs them to exit the facility.  Fire fighters can use a microphone and override the message to give occupants more specific information as needed. 

BFPE INTERNATIONAL has spent over thirty years designing, supplying, installing, and servicing fire alarm systems.   We have a design/engineering department devoted to putting together plans and submittals for AHJ review.  We have an installation department that handles both check-out & test with electrical contractors as well as turnkey installation projects.  We also have a department

devoted entirely to service, both scheduled preventive maintenance, and remedial repair work.  Since these are life safety systems, we also have on-call emergency repair technicians available around-the-clock.

 DIGITAL DIALERS

In addition to notifying occupants of an emergency situation, most fire alarm systems also activate a digital dialer to report the event to a UL listed central monitoring facility.  The central station determines what action should be taken upon receipt of a signal.  The alarm receiver is actually a computer and tells the operator the alarm zone and all pertinent site information so that they are able to relay as much detail as possible to the authorities. If it is simply a trouble condition, building personnel are notified.  If, however, an alarm signal is received, the authorities are notified, as well as building personnel. 

Sprinkler systems typically have tamper and flow switches that are activated when the water supply valve is closed and when water is flowing, respectively.  These switches are tied in to the fire alarm system as initiating zones and if either is activated, the central station is notified. 

A digital dialer utilizes (2) telephone lines to report the information to the central station.  A silent 24-hour test is sent to the central station every night to help assure that the telephone line connection is in good working order. An alternative method is long range radio frequency (RF).  This relies on a transmitter on-premises being able to send its signal to various towers that are set up in a network throughout town to reach the central station.  Another emerging technology is monitoring over the internet.

This has been a basic overview.  There are numerous alarm initiating devices other than smoke/heat detectors and manual pull stations.  Following is a more detailed description of various systems and their associated devices. 

BFPE carries a variety of fire alarm related products (i.e. heat detectors, pull station, notification devices, wire, etc.). BFPE has combed the industry and offers the finest quality products at the best prices. Add maintenance service, technical support, engineering services to this and you have the perfect solution to all your fire safety needs. Please EMAIL us your questions.