The following page appeared as a blog post at the Grace Apparatus in 2015. Any dead links and missing photos will be restored soon. Gene Brode, 6/22/17.


This write up will include the general purpose and functions of a commercial fire alarm system as opposed to a residential fire alarm system. It will cover some basics about fire alarm system components and their functions, integration with other systems, applicable codes, requirements for inspection, and certifications and training for those interested in pursuing a career in the fire alarm industry.

My intention is to lay out the basics for: those looking for more information regarding the installation of a new building fire alarm system or the upgrade of an existing system; installers or technicians who are new to the industry; anyone who is considering a career that is both exciting and demanding in a growing industry.


It should be obvious and really doesn’t need to be stated, but a fire alarm system is a life safety system that detects the presence of smoke, fire and sometimes other elements such as carbon monoxide (CO). A fire alarm is an early warning system that can notify occupants of the need to evacuate an area or an entire building. They are also one of the primary methods of preventing loss of property due to fire, along with fire alarm sprinkler systems.

Modern systems are capable of multiple functions such as notifying authorities, shutting down elevators, announcing prerecorded messages, releasing door locks, controlling air handlers and much more. I will touch on some of these system functions later on in further detail. For now, suffice it to say that fire alarm systems are a means of protecting life and property.


200px-Fire_alarm_in_Ridgewood,_New_JerseyThe first electric fire alarm systems implemented the use of coded fire alarm boxes. These boxes were mounted on poles throughout a city and communicated over a telegraph line when the handle was pulled. Each box had a unique number which was transmitted using Morse code and would alert officials of the location of a fire. Boston was the first city to have a working system like this in 1852.

(Photo credit Wikipedia)

System Sensor, a manufacturer of fire detection products, offers some telling statistics in one of its online training modules regarding current code changes. The following facts are quoted directly from the webinar “Notification Appliance Trends, Code Changes and Solutions:”

Home fire deaths have decreased from 6,015 deaths in 1978 to 2,644 deaths in 2010
Commercial fire deaths have decreased from 640 deaths in 1977 to 120 deaths in 2011
Hotel and motel fire deaths have decreased from 62 in 1980 to 16 in 2010.
You can see that the numbers have fallen greatly and System Sensor attributes this to smoke detectors and fire alarm systems. There are still a great number of fire related deaths, but fire alarms have done a lot to bring this number down. As someone who has serviced fire alarms since 2007, I can attest to the fact that many old systems remain deficient and building owners often do not wish to pay to have their systems serviced or inspected on an annual basis. It can be costly to upgrade an existing system as the authority having jurisdiction (AHJ) may compel building owners to meet current codes and standards. In considering such things one must ask, what is the cost of a human life?


While there are some major differences between commercial and residential fire alarm systems, the basics remain the same. Commercial systems are capable of much more and must adhere to stricter codes and standards. One small example is that a residential system generally is allowed to connect to only one means of communication with a central station (if at all), either via land line or cellular communicator. Current codes may allow for the use of listed cellular communicators in commercial fire alarms depending on the application and jurisdiction, but they must have two means of communication. Usually, this is done with two separate phone lines. VOiP phone lines are not an option for commercial fire alarms because data can be lost over internet phones. If cellular backup is allowed, an approved device such as a Telguard communicator must be used for commercial applications.


Fire alarm systems consist of a fire alarm control panel (FACP) which could be compared to the mother board or CPU of a computer. Initiation devices are used in the field to send signals to the FACP in the event of a fire. When the FACP receives signals it does a variety of functions: it turns on notification devices (horns, strobes, speakers) at the premises, alerts the authorities who monitor the system using a communicator, and triggers outputs to control any systems that may be integrated with it onsite.

Initiation devices can be automatic or manual. Automatic devices include smoke detectors, heat detectors, flame detectors, CO detectors. There are a variety of smoke detectors on the market for just about any application. These include ionization and photoelectric smoke detectors, duct smoke detectors (which can activate damper controls or shut down air handlers to prevent the spread of smoke throughout a building), beam smoke detectors (which are useful in facilities with high, open ceilings where spot detectors would not be suitable), and flame detectors which operate by sensing ultraviolet light, infrared light or use the aid of video technologies.

Ionization and photoelectric smoke detectors utilize two different principles. Ionization detectors rely on a radioactive element and often detect cooking fires more quickly. The ones you buy at the store are usually ionization and are not suitable for use near your kitchen for this reason. Photoelectric smoke detectors utilize a light beam which is obscured and refracted inside the smoke chamber of the detector. When smoke enters the chamber, the light bounces around until it hits the sensor and then it triggers an alarm. These are better at detecting smoldering fires, such as those due to a shorted electrical wire which may take hours to catch.

Smoke is basically an airborne particulate. Different flammable materials put off different sizes and types of smoke, some darker and some lighter. This is where having a professional becomes essential to system design and recommendations. Since smoke detectors are early warning devices, you want to make sure you have the right one for your application. Having the wrong type of detector could mean one of two things: nuisance alarms or loss of life and property.

Other automatic initiation devices include heat detectors which trigger alarms either at a certain temperature or detect the rate of rise of the heat. Fire alarm sprinklers have a flow switch built in to their main riser which can be tied in to the FACP. Other types of automatic initiation devices could include smoke detectors that activate a chemical release system (often used in large server rooms) and restaurant Ansul units which release water if there is a kitchen fire on the stove or grill.

Manual fire alarms typically refer to pull stations found near exits. They are also called fire alarm boxes or manual pull stations.


Today’s fire alarm systems are quite amazing. They are capable of being networked with building automation systems and controlled or monitored by someone at a computer or with a handheld device such as a smart phone. With the advances in technology that have come about in the past decade alone, just about every building system is capable of working together as a unit.

Current codes often necessitate this, and major disasters such as the attack on the World Trade Center on 9/11 or school shootings have pushed authorities and manufacturers to take greater precautions. Some of the common systems that often work together include fire alarms, access control systems, CCTV, air handlers and even HUGS systems for newborns in hospitals.

Emergency Communications Systems (ECS) and Mass Notification Systems (MNS) provide better protection for people in the event of emergencies such as fires, inclement weather and terrorism. The purpose of these systems is to clearly notify building occupants of what is happening and to direct them appropriately, whether that means evacuation or to seek shelter in an area of refuge within a building.

For example, if smoke is detected by a duct smoke detector, the fire alarm system activates an output or relay to shut down the furnace or close a damper. This prevents the spread of smoke which could make saving lives a lot more challenging in a deadly fire.

If the building has an elevator and there is a fire detected in an elevator lobby, the FACP will send a signal to the elevator control equipment and the elevator will go to another floor. Current codes may require that the elevator be completely shut down (shunted) if an elevator shaft or mechanical room heat detector trips. In newer systems, the elevator should first recall to another floor and then allow people enough time to exit before it drops power. There is very good reason to avoid elevators in the event of fire. They could put you right in the danger zone if they are not up to code. Enclosed stairwells are a safer means of egress because they are usually at the outside of the building and enclosed by concrete and heavy fire doors.

Systems integration is required in most buildings that have interior fire doors or electronically locked doors for access control. Fire doors are held open by magnets and a fire alarm signal will drop power to these magnets, allowing doors to shut and prevent the spread of fire and smoke. Locked doors need to allow people to get out of the building and should work accordingly.

In certain cases, as in the labor and delivery wing of a hospital, HUGS systems are used to prevent child abduction. The AHJ may decide to give priority to the HUGS system in the event of a fire. That way someone cannot trigger a false fire alarm in an attempt to gain access to the labor and delivery area to abduct a child—doors will remain locked for security so that no one can enter, but people can get out by means of a crash bar built into the door. HUGS systems utilize a matching band for mother and child that will trigger an audible and visible alarm if the bands are cut or if they go past a certain area of the hospital wing.

Current video technology can be integrated via software and can record footage that happens before an alarm event. This means that it might be possible for a system to not bog down a site’s network by recording all day long. IP cameras can be set up to record on motion (video motion detection—VMD) and are capable of producing amazing color images in low light settings and can switch to black and white images in pitch darkness. Such cameras could be incorporated into a building’s system to provide higher security in hospitals, prisons or schools. They not only serve as security features, but also as a back up to fire alarm systems where terrorists or others might try to compromise a building by getting everyone to evacuate during a false fire alarm.

Fire alarm systems have long been capable of communicating with an entire building via an All Call feature where emergency personnel can give a message over the fire system’s speakers that are throughout the building. Some systems offer fire alarm phones that firefighters can take with them and communicate back to the command center using jacks situated throughout the building. Cutting edge systems may even offer a graphic annunciator screen which can help responders to see where a fire originated and which way it is moving.


There are many options for the monitoring of fire alarm signals that the FACP will send. Fire alarms and trouble signals can be monitored 24-7 by a Central or Remote Station. These are the two most common types of monitoring centers. Universities or hospitals that have multiple buildings may be monitored onsite by their own personnel, and some systems may even have a direct line to the fire department or emergency dispatch center. It all depends on the type of building and the AHJ.


Generally speaking, the NFPA 72 requires an annual inspection of your fire alarm system. Some AHJ’s really enforce this, others are more lax. I usually go back to the question I posed under the FACTS section: What is the cost of a human life? If the AHJ does not enforce an annual inspection, is it worth it to you to save some money by not testing, cleaning and inspecting your system if someone in your building perishes? You can’t put a price tag on this. Fire alarm systems need to be inspected and tested at least annually, maybe more depending on the type of business you operate.

Just because the fire alarm panel sees everything as normal does not mean that you have a functional system. It’s a piece of electronic equipment and prone to have problems just like every other electronic device out there. How many people do you know that drive a 20-year-old car or still use a computer from 1980? Not many. We are talking about life safely, not the old grocery-getter.

Systems need to have a primary power supply (110 VAC) and secondary power supply (12 or 24 VDC batteries) and these need to be tested to see if they will last for the duration of time the code requires of your system in a power outage. Batteries must be replaced at least every five years. Generally they don’t even last that long as far as load voltage test is concerned. Test your batteries and replace them when necessary!

Smoke detectors get dirty. When dust covers the outside of a detector, smoke may not enter the chamber freely. The result is that the detector will not trip unless maybe there is a lot of smoke, and by then it could be too late. If dust accumulates inside the smoke detector, nuisance alarms may occur. Generally, once the fire department has been dispatched they will not turn around if someone calls to cancel. Regular cleanings will lower false dispatches and prevent companies from wasting money on fines they may incur.

Smoke detectors are tested by spraying an approved aerosol into the smoke chamber. Some facilities are required to test the sensitivity of their smoke detectors, usually every other year. This can be done with a device which measures the amount of aerosol that is sprayed into a cup held over the smoke detector, or it can be done electronically. System Sensor makes a tester that reads their detectors and displays the sensitivity level. Intelligent systems constantly monitor all intelligent devices and are capable of displaying the various levels of a detector. Sensitivity levels can be adjusted and the system may even have a drift compensation so that it adjusts the level automatically to prevent false alarms.

Some heat detectors can be tested, others cannot. Intelligent, or addressable, fire alarm systems can be tested without damaging the unit. Fixed analog heats have a fusible link and must be replaced once they reach their peak temperature. These cannot be tested at all. Heat detectors can be tested by using a hair dryer or other heating device. Testing devices made specifically for this purpose are best as they put out a measured amount of heat and will not damage the device. Beam smoke detectors have filters that are passed in front of the beam to simulate the obscuration caused by smoke, while a complete blockage of the beam causes a trouble at the panel.


The code book is big and changes every couple of years, and even then the AHJ has the final say in how they want your fire system to function. There are sections about the type of detectors to be used as well as the spacing between them. This is also true for notification devices which, if installed improperly, will not be sufficient for people to see or hear if there is a real fire.

Some occupancies require special audio and visual considerations, as in hotels and other dormitory areas. The tone needs to be loud enough to alert someone who is sleeping and may be hearing impaired. Beginning with the 2010 NFPA72, the tone has been changed for audio devices. Consult your fire alarm contractor and your authority having jurisdiction to find out what is acceptable for your building.

Don’t take shortcuts. If you need to add onto your existing system, find out what is required. Sometimes adding onto a building does not mean that you have to upgrade the entire system in the existing building, but you will need to follow the present codes and standards in the addition.


Some states require workers to hold a fire alarm license or a NICET certification in their particular field. Basic training for electronics and drafting may be available at career or technical schools, or even on the job. The fire alarm industry employs installers/programmers, inspectors, service technicians, engineers/designers, sales and probably more depending on the specific project. Some colleges offer degrees in fire alarm engineering for those interested in system design. A good technician will be knowledgeable of a variety of systems, understand how systems are installed and how to troubleshoot both equipment and wiring circuits. Installers, technicians, designers and sales staff ought to have a good knowledge of codes and standards, know the limitations of fire alarms systems and how that pertains to their customers’ systems, and be able to make good recommendations for improving or expanding a fire alarm system.


National Fire Protection Association
American Society of Certified Engineering Technicians
National Society of Professional Engineers

Fire Alarm Signaling Systems
National Electric Code (NFPA 70)
National Fire Alarm and Signaling Code (NFPA 72)
Life Safety Code (NFPA 101)
Please feel free to contact me for further information at genebrodejr at gmail dot com or leave a comment below.