Automatic Sprinkler and Fire Alarm Systems

Don’t believe everything you see in the movies; here is a layman’s guide to fire sprinkler and fire alarm basics.

The myths and misconceptions surrounding fire alarm and fire sprinkler systems in movies and television is pretty staggering. As a design professional, I roll my eyes every time I see a character activate a manual pull station resulting in every fire sprinkler going off. Of course you might say, “It’s a movie; lighten up!”. On one hand; you’re right. It is only fiction. On the other hand, the consistency in which fire alarm and fire sprinkler systems are incorrectly shown actually leads to complacency and misunderstanding. In the not so distant past, I actually explained how a sprinkler works to a coworker, and they were floored that what they’d see in the movies was not correct. Entertainment is fine; I’m a big movie person myself. When no one actually explains how the systems really work to the average person, and the movies are all they know, it could actually lead to a delay in evacuation or other events that could put a person’s life in danger. I’m not suggesting changing the movies; let’s just talk about how the systems actually work. I’ll try and do so in the least technical way possible. To start, here’s some examples (from two movies I actually like) of movie imagination with regards to fire alarm and sprinkler systems. After the show, I’ll follow with some basic concepts and history for you:

Concepts and History:

Automatic sprinkler and fire alarm systems are two crucial components of a building’s life safety systems. They are what’s known as active protective systems. Passive protective systems such as fire-resistive construction, protected stairways, smoke barriers and fire walls are intended to be the main line of defense in the protection of occupants against a fire. Fire alarms are there to actively notify occupants of a fire so they can evacuate, and automatic sprinkler systems are intended to help suppress the fire long enough for the fire department to arrive and extinguish the blaze. While typical light-hazard sprinklers may often extinguish a small fire, their purpose is to keep it from growing; not put it out. More specialized systems are actually designed to fully put out a fire, but those are normally reserved for high hazard occupancies such as large storage buildings, hazardous material handling and very large mercantile buildings such as big box stores like Home Depot, Costco or Walmart.

Automatic sprinkler systems have been in existence since the late 1800’s, beginning with Henry S. Parmelee’s invention of the first sprinkler head in 1874. While improvements have been made in sprinkler design and the various system components, such as valves and piping; the basic concept of automatic sprinkler systems has not changed that much in almost 150 years.

The earliest fire alarm systems involved nothing more than a person keeping watch in the streets who would then alert the fire brigade. With the invention of the telegraph in the early 1840’s by Samuel F. B. Morse, cities such as New York began to construct municipal alarm systems of communication between fire stations and government buildings. This reduced the time needed to alert the fire brigade and improved response time through better directions. By 1880, manual fire alarm signal boxes had been patented by John Gamewell and his brother-in-law James M. Gardiner. At that time, the Gamewell Company held a 95% share of the United States market for fire alarm systems. William B. Watkins designed the first electric fire sensor / heat detector in the early 1870’s and in 1873 formed the first private fire alarm company, Boston AFA; known today as AFA Protective Systems.

In the early 1900’s, leading fire alarm and fire sprinkler companies such as ADT (American District Telegraph), Holmes Protective, AFA, Grinnell and Automatic Fire Protection (AFP), established contracts with each other to supply detection equipment, sprinkler systems, sprinkler system supervisory equipment and central station monitoring services.

In 1939, Swiss physicist Ernst Meili invented an ionization chamber which could detect combustible gases in mines and a cold cathode tube that could amplify the small signal generated to a level sufficient to activate an alarm. By 1951, the first ionization smoke detectors were sold in the US. The photoelectric (optical) smoke detector was then invented by Donald Steel and Robert Emmark of Electro Signal Lab in 1972. The technologies and devices used in fire alarm systems have continued to advance, but the basic concepts remain the same.

Fire Alarm Systems: The Basics

Fire alarm systems are required to be installed in accordance with NFPA 72, the National Fire Alarm Code. (Disclaimer: The following explanations are in layman’s terms and intentionally omit and generalize some technical details, devices and system components for clarity).

Fire Alarm Systems are made up of three basic categories of devices:

  1. Initiating
  2. Notification
  3. Control / Transmission

Initiating Devices:

These components do exactly what you think they would; they initiate an alarm. They include both automatic and manual means of activating the alarm system. The most common manual device is the “Manual Pull Station”. This would be the red device on the wall labeled “Pull in case of fire” or something similar. When the handle of this pull station is moved it literally flips a switch inside the box that tells the system to go into “Alarm”.

The three most common automatic initiating devices are smoke detectors, heat detectors and sprinkler system flow switches. The first two are self-explanatory. When a smoke detector sees (or senses) smoke, it tells the system to go into alarm mode. If the heat detector senses a rise in temperature above a set point, it also tells the system to go into alarm mode. The third item is a component that few people outside the construction, design, or fire protection industries even know exists; the flow switch. A flow switch is a device installed into the piping of the fire sprinkler system just after the water pipes enter the building. The typical flow switch has a round “paddle” or disc that is directly inside the pipe and connects to a lever and electronic sensor. When the sprinkler system activates, water begins to flow through the pipes. When the water moves, this ‘paddle’ also moves; raises the lever and sets off the sensor. This tells the fire alarm system that a sprinkler has activated; also resulting in an alarm.

In a typical light-hazard occupancy sprinkler system ,which are the most common, this is the ONLY interaction between the sprinkler system and the fire alarm system. When water flows; the alarm goes off. It does NOT work the other way. Setting off the fire alarm DOES NOT activate any or all of the fire sprinklers. Unless the system being discussed is for very unusual situations like hazardous materials, locations with jet fuel, etc.; the fire alarm system and sprinklers are not set off electronically in any way. We’ll discuss how a sprinkler system works next.

Notification Devices:

These include two main appliances, commonly referred to as a horn and a strobe. The horn is what it sounds like; it’s that really loud and annoying noise maker that lets you know there is a fire and to GET OUT. The strobe is the light emitting device that flashes when the alarm activates. Strobes are there in case occupants are hard of hearing or ambient noise levels are high enough to prevent people from hearing the horn. The horn can also be a recorded announcement in some occupancies. These two devices are there to let you know a fire or another emergency is present and you need to act accordingly. Very commonly both devices are combined into a single appliance called… you guessed it: a horn-strobe. We look for humor in this subject matter wherever we can find it.

Control / Transmission Devices:

This is my own general category for the main Fire Alarm Control Panel (FACP), Fire Alarm Annunciator Panels (FAAP), and automatic dialing devices. All of the initiating and notification devices are connected to the FACP. When an initiating device is tripped, the FACP activates all of the notification devices to let people know there is a problem. If any systems are required to shut off when an alarm is activated (mechanical units, electronic door locks, magnetic door hold-opens, etc.), the FACP will send signals to that equipment accordingly. Most modern FACP’s also include the auto-dialer device. This is literally a phone / modem that calls a monitoring service and says, “We have an alarm. The following initiating devices were set off….” The monitoring company will then notify the fire department. As all of this is done electronically, there is very little delay between when a device is set off and when the fire department is notified. The FAAP (as shown below) is basically a twin to the control panel from the FACP that can be located at strategic locations without having to install the larger control box in public areas.

Fire Alarm Systems

Those are the fire alarm basics. Although the wiring, programming and code requirements surrounding what devices are required, where they go, and how they must work are more complex, the basic concepts of initiation, notification and transmission are pretty simple.

Fire Sprinkler Systems: The Basics

Automatic Fire Sprinkler Systems must be installed in accordance with NFPA 13, NFPA 13R or NFPA 13D. 13R is generally for multifamily and hospitality occupancies like apartments, condos, hotels, motels and dormitories. 13D systems are for single family homes or duplexes. The NFPA 13 compliant system is what you would normally see in any commercial, institutional, educational or other public type building. The 13R and 13D systems use the same types of sprinkler heads; they just have less restrictive requirements in where sprinklers are required, and what kinds of equipment and other devices are installed.

The central component to a sprinkler system is… no big surprise: the sprinkler.

Fire Sprinkler
Typical ‘pendant’ type sprinkler head

The most typical sprinkler installed has 4 main parts:

  1. The cap: a disc that covers the hole the water shoots out of;
  2. The thermal linkage: the colored glass tube or metal piece that bursts or melts at a certain temperature. The linkage holds the cap in place;
  3. The deflector: The metal disc or plate that the spreads the water out, and
  4. The frame: the “arms” of the sprinkler head that hold the deflector, cap and linkage all together.

So how does a sprinkler go off? Its rather simple. The most common thermal linkage you will see today is a glass bulb with a colored liquid inside. That liquid is a mixture of water and alcohol or glycol with a colored tint. The color indicates the temperature at which the bulb is designed to burst. Per NFPA 13, bulbs that are red in color activate at 155°F. Other colors such as green, yellow, or blue indicate higher temperature ratings.

When a fire gets large enough to raise the air temperature in a room (at the head itself) to a level equal to or above the head’s rating; the glass bulb bursts. With nothing to hold it in place; the water pushes the cap out of the way; water rushes through the opening (called the orifice), and then spreads out in a pre-defined pattern as it hits the deflector. That’s how a sprinkler gets activated. There are no electronics, no manual levers or special keyed switches. The bulb gets hot; it breaks; water comes out. The only heads that will go off in a fire are those that have been heated to that specific temperature.

If EVERY head went off in a building at once (as the movies like to show), the amount of water necessary would be as much as fifty to a hundred times greater than any normal building has available. Sprinkler systems are designed to have no more than 4-6 heads go off in a fire (that is a very general statement I know; the exact number of heads is a code requirement and up to the system designer and is dependent on a number of different factors). What you see in the movies is just not physically possible in any typical building. There are specialized systems in which a large number of heads are activated at the same time, but those are not used in any building the general public normally occupies.

There is of course more to a sprinkler system than just the sprinkler heads. Every head is connected to pipes made of steel or CPVC (specially designed plastic pipe). The pipes with heads on them are commonly referred to as branch lines, while the larger pipes that feed the branch lines are called mains. The single big pipe that supplies the mains is called the riser. The riser is located inside the building right after the main water pipe enters the building. The riser typically includes shut-off valves, pressure gauges, test valves, the flow switch (connected to the fire alarm system as mentioned above), backflow preventers, and other devices needed to maintain and test the system. A typical NFPA 13 system will also have a Fire Department Connection (FDC) at the riser (or a remote one that connects to the riser) which allows the fire department to connect a pump truck and supply the system with a higher flow and pressure than the normal water system may be capable of.

Main riser with valves, main drain and pressure gauges

The kind of system described above is known as a “wet” system because the pipes are always full of pressurized water. Water freezes however, so another common system known as a “dry pipe” system is often used in attics or other areas where no heat is available during winter months. In this system, the heads are actually the same, but the branch lines and mains are filled with compressed air. The water from the utility provider is kept at bay in the riser, by a special valve and the compressed air in the system itself. When a fire causes the sprinkler head bulb to burst, the process is the same, except the system has to first purge itself of the compressed air, and then the water comes rushing in behind. Same concept; it just slightly delays the water actually hitting the fire.

The basic concepts and components of a fire alarm and fire sprinkler system are not difficult to understand. In fact, they are simple enough that everyone should know how and when each system would go off, and how it generally works. Knowing these basics makes using them that much easier and safer.

Would you like know more?

This is a VERY broad overview of fire alarm and fire sprinkler systems. What components or requirements of these systems would you like to know more about?

Sources, Disclaimers and Copyrights:

  • Fire Alarm System Research – Where it’s been and where it’s going, Wayne D. Moore, P.E.

  • Sprinkler image: Courtesy of
  • Fire Alarm device images are the property of Potter Roemer Fire Pro., Copyright 1937-2016
  • Fire alarm control and annunciator panels images are the property of Silent Knight, by Honeywell, Copyright 2017.
  • Excerpt from Lethal Weapon 4, Copyright Warner Bros. Pictures, 1998
  • Excerpt from Casino Royale, Copyright Columbia Pictures, 2006
  • Fire Truck Image is the property of the City of Leander Texas Fire Department (actually one block from my office; thank you gentlemen).
  • Fire riser image is by DFD Architects, Inc., Copyright 2017.

All images and videos included or linked to are for reference and educational purposes only. All copyrights are the property of their respective owners.

Disclaimer: I am not a licensed fire alarm or fire sprinkler RME (Responsible Managing Employee) or installer. All fire alarm and fire sprinkler systems shall be designed and installed by appropriately licensed professionals in accordance with applicable state and local laws. The above commentary is from my personal experience and code knowledge, but should not be substituted for advice and direction from trained and licensed professionals in fire alarm and fire sprinkler design and installation.


Architects are their own worst enemies

From my own experience, the public’s opinion of architects in general is still a positive one, but the architect’s reputation within the construction industry and among those who inspect various building types is not complimentary. Why is that? Have architects created an unreasonably high opinion of themselves?

Few professions can be described in a single word (or two). Those that can often date back hundreds or thousands of years into history. Every profession that spans centuries is going to change and adapt to changes in culture, science, technology and the needs of society in general. The job of an Architect is no different.

So what is an Architect?

“architect: a person who designs buildings and advises in their construction”(1)

The preceding definition is a much more modern summary of an Architect’s role and responsibilities than the concept of a “Master Builder”; the predecessor to the Architect of today.

“Master Builder: a person notably proficient in the art of building; the ancient Egyptians were master builders; specifically:  one who has attained proficiency in one of the building crafts and is qualified or licensed to supervise building construction”(1)

Many Architects would like to think of themselves as following in the footsteps of the Master Builders of the Greek, Roman and Renaissance eras where the roles of designer, builder and craftsman were commonly embodied in only a select few. Early famous architects such as Vitruvius, Palladio, and later figures such as Thomas Jefferson gained notoriety and respect through experience, reading, apprenticeship and self-study. As the world population increased and people’s skills became more specialized, the role of the Architect moved away from the actual construction of the built environment to a focus more on design and took on an advisory role in construction. Considering the increase in size of projects and complexity of materials and systems used in construction today, this isn’t a surprising development. Many architects today however have become distanced from the realities of construction, with some college graduates unable to draw the most basic of details regarding framing or similar trades, and many architects never even stepping foot on a construction site until well into their careers.

In 1857, the American Institute of Architects (AIA), the primary professional organization for architects in the United States was founded to “promote the scientific and practical perfection of its members” and “elevate the standing of the profession”. (2)

Prior to the founding of the AIA, “anyone who wished to call him-or herself an architect could do so. This included masons, carpenters, bricklayers, and other members of the building trades. No schools of architecture or architectural licensing laws existed to shape the calling”.(2) The architectural profession evolved out of those individuals with the knowledge and experience to design and construct a building.

Prior to 1897, no legal definition of “architect”, nor any requirements for an architect’s education or licensing existed until Illinois became the first state to adopt architect licensing laws.(1) Today, all fifty states, through joint efforts with the National Council of Architectural Registration Boards (NCARB) and the AIA use a mostly standardized system of certification and testing for the task of licensing architects. While the original goal of setting standards for what defined an “architect” was in the best interests of the general public, the modern definition of an architect and the profession was founded on the desire to promote for the improvement of those calling themselves architects and to elevate the profession itself. Please do not misinterpret this as a statement against the requirement of licensing architects. On the contrary; I fully believe that it has, and will continue to be, of the utmost importance.

Today, the objects of the AIA, “shall be to organize and unite in fellowship the members of the architectural profession of the United States of America; to promote the aesthetic, scientific and practical efficiency of the profession; to advance the science and art of planning and building by advancing the standards of architectural education, training and practice; to coordinate the building industry and the profession of architecture to insure the advancement of the living standards of people through their improved environment; and to make the profession of ever-increasing service to society.”(2)

While the architectural industry and society in general has greatly benefited from minimum standards of education and training for architects in the United States (in large part due to the efforts of the AIA and its members), the current role that architects play in society varies significantly. The realty of whether the architect of today is fully capable of protecting the health, safety and welfare of the general public is a topic of great debate depending on your point of view and role in the design and construction industry.

For better and for worse

From my own experience, the public’s opinion of architects in general is still a positive one, but the architect’s reputation within the construction industry and among those who inspect various building types is not complimentary. Why is that? Have architects created an unreasonably high opinion of themselves?

The architect has historically been looked up to as an expert in a field of specialized knowledge. Architects are required however to be generalists; knowing a little bit about every trade and discipline they oversee, but not directly in control of the construction or engineering of a project. The architect is looked upon to provide direction and advice to those constructing a building, as well as organizing the various engineering disciplines that are needed. The role of an Architect has often become that of a manager; settling disputes between the owner, contractor and other entities. While architects will always play a key role in the design and production of construction documents; other than in a small percentage of high profile and high priced projects, the owners and contractors are the large guiding force in the design process. The architect often takes a backseat role in the decision-making process during construction (and even earlier on). Is this appropriate? Yes and no. Unless an architect has a partial ownership in the project, it’s not their money. Many architects may say that good design is the most important part of their job, but a gorgeous building that leaks or is a danger to its occupants is a failure (Refer to my previous post on the Grenfell Towers in London).  Their responsibility at a core level is to protect the health, safety and welfare of those persons that will use, occupy and are affected by the project. Would you rather occupy a building that is pretty and dangerous to your safety or a so-so building that protects you? Of course, we’d like the best of both, but that would require architects to step up and recognize that their technical expertise in building codes and fire safety is just as, if not more important, than their design talents. Meeting their clients budget and design goals is absolutely critical, but never at the expense of a person’s health or safety.

You might ask, “Don’t architects have to know all the codes and don’t they learn that in school? Isn’t the ability to protect us the most important part of their job?

The real answer is scarier than you think.

I’m going to quote another architect, who blogs under the name of Sheldon. I do not know him on a personal or professional level, and I will not make any statement about his qualifications, knowledge or character. I only want to address the statements he made, as I don’t not think he is alone in his opinion and he brings up assumptions that I think are the reason that others view of architects has degraded:

The labyrinthine regulations of the federal government reminded me of regulations we in construction deal with every day. They are similarly complex and obscure, differing only in extent. I was not surprised that I didn’t understand the subjects of the senate hearing, but on further thought, I realized I really don’t know much about the countless codes and regulations that govern construction. Nor, I’m sure, does anyone else.

The picture that accompanies this article shows just a few of the code books we use at my office. In the picture are a few versions of the IBC, a couple of Wisconsin code binders, several books of Minnesota codes, a few versions of NFPA 101, an elevator code book, and a few books that explain what’s in the codes. This collection is nowhere near complete; we have many additional code books for Minnesota and Wisconsin, plus others for North Dakota, South Dakota, and Iowa, as well as for a couple of other states. I can only imagine what national and international firms have in their libraries.

Presumably, when someone certifies documents, that certification implies that the responsible person (or someone under that person’s direct supervision) understands everything in every statute, code, rule, and regulation governing the work of the project, and that the project complies with all of them. What does that tell us?

First, I think it’s safe to say that most of most regulations simply codify what was already common practice, much of which was based on empirical evidence. We build walls of 2 x 4s at 16 inches on center because it’s been done that way a long time and it seems to work. Later additions were added after due consideration; someone probably tested walls with framing at 24 inches on center and that worked, too.

Many requirements were added in response to building failures. Even then, I suspect much of what’s in the code is based on intuition, rather than on basic research beginning with the question, “What is required?” Though useful for comparative evaluations, code requirements often are not based on real-world applications. (See “Faith-based specifications.”)

I also think it’s safe to say it’s unlikely that any building complies with all regulations. Regardless of the source or value of those requirements, it’s clear that there are too many for any one person, or even several people, to understand. Making things more difficult is the fact that some information is restated in different codes, often in slightly different fashion, and some codes are more restrictive than others.

The International Code Council (ICC) publishes a dozen or so building and fire codes, which reference hundreds of standards published by ASHRAE, ASCE, and various other organizations, including about 50 of the 375 published by NFPA. These secondary codes also cite other standards, and so on, and so on, and so on. States then modify the basic codes, as do local jurisdictions. Some variations are required by local seismic and weather conditions, but many make little sense. All of these form the basic reference library for everyone involved in construction. Codes are continually being updated, usually on a three-year cycle. But not everyone is on the same cycle; some states update to follow the major codes more quickly than others, and different states will use different versions of the same codes.

My firm does mostly medical work, which must comply not only with the IBC and state codes, but also with NFPA 101, dictates of the Centers for Medicare & Medicaid Services and the Joint Commission, as well as requirements of individual clients. I’m sure we’re not alone, and that other types of construction have similar additional requirements.

Is all of this really necessary? I concede that there are special situations that require special treatment, but it’s hard to believe there are enough special circumstances to justify the mountain of code books we must deal with. While it is somewhat understandable that we have codes for specific conditions, there is no excuse for conflicts between different codes. (4)

As a licensed architect who currently works in the healthcare design industry, a former inspector / surveyor for the State of Texas, and therefore also a federal surveyor working on behalf of the Center for Medicaid and Medicare Services (CMS); I am appalled that any architect would admit that, “I realized I really don’t know much about the countless codes and regulations that govern construction. Nor, I’m sure, does anyone else.”.

The dozens of building and fire codes, standards and other regulations under which the healthcare industry operates are all critically important to the safety of those residents and patients that reside in any facility. Codes and standards are NOT based on “intuition”, they are based on actual building failures and tragedies such as the Triangle Shirtwaist Factory fire(5), the MGM Grand Fire(6), and the Station nightclub fire(7). Building codes and all their referenced standards and testing procedures exist for the sole purpose of protecting the lives of people that cannot protect themselves (as is the case for healthcare occupancies), or allowing those who are capable the time to reach safety in the event of a fire or other emergency. All codes and standards have their limitations and fallacies, after all they are written by human beings with biases and their own agendas; Therefore, codes and standards are written by groups of people, with the hopeful intent of avoiding personal preferences. This process also allows for codes to change over time when new information is available or lessons have been learned. Understanding the complexities of the codes and standards is not easy, but that’s why the task is delegated to individuals with the skill set and desire to understand them. Its our job.

Many architects have lost (if ever had) their connection to the real-world requirements of constructing a building, and most do not understand the most important part of their profession, and that is the protection of those that occupy the buildings they design. If those professionals (architects) that are tasked with the responsibility to ensure buildings are made safe are not capable of doing so, how on earth can they expect owners, contractors or anyone else to take up that charge?

I am not implying that all architects are guilty of ignoring their responsibilities, nor am I suggesting that I, in any way, am guilt-free. I want to bring attention to the fact that the architectural industry (including the educational side) has put a huge emphasis on the artistic and design aspects or architecture and have grossly ignored the importance of safety and code compliance. This has led to the common opinion of many contractors and owners that architects are egotistical and know nothing of the real world.

I could write an entire post about the fact that my own Alma-mater’s curriculum included only a single one-semester class (one hour, twice a week) on building and life safety codes over the course of a five-year professional bachelor’s degree program, and  then more than half of my class that year failed the course. That’s not unfortunate; its shameful.

So why are architects their own worst enemies? Many of the architects I have met and worked with are incapable of checking their egos long enough to learn the realities of the construction industry and embrace the critical importance of building safety and the codes that facilitate that goal. They instead have taken a combative stance against the codes and those jurisdictions that adopt and enforce them. I tell people constantly that if they don’t agree with the code; get involved and change it. Complaining about the codes only shows one’s ignorance of their role and importance.

Architects must embrace the incredible responsibility they bear on behalf of society. The task of keeping others safe should be a humbling one, not a reason to, “elevate the standing of the profession”. That should be a result, not a goal.

Action; not words

There are of course many more facets of the architectural profession that I did not address such as environmental responsibility, efficiency and preservation that are discussions unto themselves.

I am a licensed architect and I am proud to call myself one. I make a lot of mistakes, and I often let my ego get in the way of what’s right, but I recognize that, and I’m always working to improve.

I put the challenge to every architect (or those working with architects and/or towards the same goals); treat this profession with the respect it deserves by fulfilling the expectations society puts on you. Learn everything you possibly can about the codes, regulations and standards you are charged with upholding. Think of the people your designs protect and shelter first; your own ego and gratification should be the lowest of priorities.


(1) Definitions:

(2) History of The American Institute of Architects

Archived/ at

(3) American Institute of Architects Bylaws, Revised April 2017

(4) Constructive Thoughts, Observations and musings about architecture and the construction industry.

(5) The 1911 Triangle Factory Fire

(6) MGM Grand Fire

(7) The Station nightclub fire

Featured Image from: