A Guide to Fire Alarm Basics – Initiation

A fire alarm system is a crucial part of the overall fire protection and life safety strategy of a building . A fire alarm system serves many functions and the differences between the functions can be a bit confusing, so I created a visual guide to fire alarm basics. The objective of this blog series is to discuss some of the major components and functions of a fire alarm system. For an overview of the entire system take a look at my Guide to Fire Alarm Basics Blog. This blog will take a deeper dive into the initiation portion of a fire alarm system. The main function of the initiation portion of a fire alarm system is to report the status of a protected space or the existence of a fire. The components include all devices and circuits that send a signal to a fire alarm control unit (FACU) such as heat detectors, smoke detectors, carbon monoxide detectors, water flow switches, manually actuated devices, and pressure switches. Depending on the system, the signal from an initiating device can create an alarm condition or a supervisory condition. Based on the type of detectors and FACU, the signals can be sent over an initiating device circuit (IDC) for conventional systems, or a signaling line circuit (SLC) for addressable systems. Conventional initiating devices are typically detectors that use a switch contact to short both sides of the initiating device circuit together. By doing so, the initiating device causes an increase in current flowing through the circuit, which the FACU interprets as an alarm signal. Once one device shorts the circuit, no other device on that circuit or “zone” can send a signal. Because of this, any device on the circuit or “zone” will put the entire zone into an alarm state. Zones are typically designed to enable someone to easily identify an area where the alarm is located, for example, in a school you may have a gymnasium zone circuit and an auditorium zone circuit that each contain multiple devices. Addressable devices are either initiating devices or control/notification appliances that are capable of communicating a unique identification number or address to a control unit via a signaling line circuit. This identification consists of a binary string of 1s and 0s that indicate the address or location of that device on the circuit. When the FACU polls an initiating device, the initiating device responds with its status (Normal, Alarm, ect.) and address. The device address allows for the location of the detector to be identified at the FACU. When one initiating device is activated on a signaling line circuit, the FACU is still able to poll the other devices unlike a conventional initiating device circuit. Additionally, some addressable initiating devices are able to also transmit to the FACU a range of values of smoke density, temperature variation, water level, water pressure changes, and other variables. And then the control unit software determines the set points for initiation of an alarm, supervisory, or trouble signal. These types of initiating device circuits are known as analog addressable as they are able to tell the FACU their address and their value.   Ionization smoke detectors utilize a small amount of radioactive material to ionize air molecules into positively and negatively charged molecules that create a small electric current. The introduction of smoke into that ionized air will reduce the amount of current and cause an alarm signal.   Photoelectric smoke detectors utilize a light source and a photosensitive cell. When smoke enters the chamber, light scatters and is picked up by the photosensitive cell, causing an alarm signal. A beam smoke detector is like a photoelectric detector, except it is designed to cover a large area. A transmitter and receiver or reflector are placed to create a light beam across a space, when the amount of light being received by the receiver or reflected to the transmitter falls below a certain percentage, an alarm signal is sent. A non-restorable fixed temperature heat detector utilizes solder that holds up a plunger. The solder melts at a specific temperature and causes the plunger to drop, which shorts the contacts and causes an alarm signal.   A restorable fixed temperature heat detector utilizes two metals that have different thermal expansion coefficients. At a specific temperature, these metals will bend and cause the plunger to short the contacts, which causes an alarm condition. When the metal cools it will bend back in the other direction and restore itself.     A rate-of-rise detector utilizes an air chamber and a diaphragm. When a fire causes the air in the chamber to expand faster than it can escape out the vent, the increased pressure forces the diaphragm to close the contacts and initiate an alarm signal. This rate-of-rise detector also contains a fixed temperature plunger that will operate if the temperature exceeds the determined temperature.     An analog addressable heat detector utilizes a thermistor element to constantly monitor the temperature. The response criteria, which can be a temperature above a specified level, or a specific rate of rise in the temperature, is programmed at the FACU.   There are many different types of carbon monoxide (CO) detectors. One example of a CO detector is a Colorimetric detector. Like a photoelectric smoke detector, this detector contains a light source and a photocell that are constantly measuring for light being reflected from a chemical detector. In the presence of carbon monoxide, the chemical detector will change to a black color and light will no longer be reflected to the photocell, which will result in an alarm signal.   Sometimes called manual fire boxes, pull stations, or call points, manually actuated initiating devices initiate an alarm signal when there is an input from a person, such as pulling a lever or pushing a button. These can require multiple actions to initiate such as lifting a cover or breaking glass prior to actuating the device.   Flow switches are installed inside the piping of a sprinkler system and have a vane that moves with the flow of water. When water begins to flow within the pipe, the vane operates a switch that initiates an alarm.     Pressure switches are installed on sprinkler systems to monitor for a change in water pressure. A signal will be sent to the FACU when there is an increase in water pressure, which means that water is flowing though the sprinkler alarm valve. Want to Learn More? Like I noted in the beginning of this blog, if you are interested in learning more about fire alarm basics, take a look at my Fire Alarm Basics Blog. I will be updating this series over the next few months to add a deeper dive into different portions of the fire alarm system. If you found this article helpful, subscribe to the NFPA Network Newsletter for monthly, personalized content related to the world of fire, electrical, and building & life safety.

Join NFPA as we Celebrate 125 Years of Protecting People and Property; Anniversary Conference Series Kicks off on May 18 with Electrical Program

NFPA is celebrating its 125th anniversary this year and we want to commemorate this momentous milestone with you! Since our founding in 1896, NFPA has been devoted to eliminating death, injury property, and economic loss due to fire, electrical, and related hazards. Working side-by-side with our members, colleagues, and countless other fire and life safety advocates from every industry across the globe, we have had a major impact on the public’s safety – we’re proud of the strides we have made over the past few decades in reducing the fire problem worldwide.  So it is with great excitement we’re announcing NFPA will be hosting a series of events and initiatives throughout the year that pay homage to the Association and its long history of dedication and collaboration. Key to the celebration is the launch of a virtual 125th Anniversary Conference Series that replaces the traditional in-person 2021 NFPA Conference & Expo. The series features 10 one-day programs for building, electrical, and life safety professionals and practitioners that collectively offer more than 100 informative education sessions, engaging content, industry roundtable discussions, networking opportunities, live chat sessions, and exhibitor demonstrations. Led by leading industry experts, the program sessions cover a broad range of topic areas from the impact of new technology on codes and standards and the use of data to drive safety, to community risk reduction and public education strategies aimed at protecting people and property. The sessions are designed to help you adjust to changing industry needs and more effectively and efficiently perform your daily work. The online conference series runs from May 2021 through March 2022 and will be available on demand during the year to allow for more schedule flexibility.  For those in the electrical industry, you do not want to miss the first program of the series that kicks off on May 18. The “Empowering Electrical Design, Installation, and Safety” one-day program has two learning tracks and nine sessions that focus on issues related to design and installation, new and emerging technology, and workplace safety in the electrical landscape. Whether you attend the live event in May or view the content on demand, the program will help you sharpen your skills and improve your knowledge as you earn CEU credits. Find out more on our webpage. With so much to celebrate, we hope you’ll join us for this year-long, unique educational opportunity. A safe world is our priority, and we look forward to our continued progress, working with all of you, during the next 125 years and beyond! Visit nfpa.org/conferenceseries to learn more about the series, the electrical program, and to see the full roster of upcoming events.
Exit doors

The Basics of Swinging-Type Egress Door Operation

Door assemblies serve multiple purposes that relate to the comfort and safety of building occupants. They provide protection from weather, reduction of noises from adjoining areas, prevent trespassing by unauthorized persons and slow or stop the spread of fire and smoke. While seemingly so commonplace, door assemblies can become an impediment to occupants if they are locked or inoperable.  Doors within a means of egress include those non-fire-rated, fire-rated and smoke-resisting door assemblies. None of these will perform properly if left open during a fire. There are many examples of fires where fatalities resulted because of doors that were left open. There are also examples of fires where lives were saved because a door leaf was closed. Unfortunately, there are those fires in which door openings needed for escape were blocked or locked, resulting in devastating losses. Just this week, an eight-alarm fire in Queens, New York City, displaced 240 residents and injured people, including 16 firefighters. The fire was reported to start in a unit on the top floor.  An occupant fleeing the building left the door open to the apartment unit, causing the fire to spread into the hallway and to other areas of the building.    To help ensure safe door operation during an emergency, considerations must be given to the type of door, width of opening and door leaves, door swing direction, encroachment, the force required to operate the door, and the locking and latching devices. Here we will focus on those fundamental operational features only for side-hinged or pivoted-swinging type egress doors as these include the majority of doors an occupant will likely face while egressing a building. Other door types may be permitted in lieu of swinging doors but these will be addressed separately.   Minimum Width Door openings must be of sufficient width to ensure that enough people can pass through the openings quickly and safely during egress. Too narrow of an opening, or not enough total available capacity can create bottlenecks, and obstruct the flow of occupants leaving as they move towards a safer area.   Minimum door width is prescribed as (1) clear width, (2) egress capacity width, or (3) leaf width and when a specific minimum width is required by the Code, the specific width will be refenced. Specifying a door leaf width (the width of the door leaf, not the opening) is the least common case, and more often a minimum clear width or egress capacity width is mandated. Door width measurements might be used in calculating egress capacity or in determining if a minimum door width requirement is met. Depending on the purpose for which the door width measurement is used, the allowable encroachments on opening width vary.   Measuring egress capacity width for a new door leaf that opens 90 degrees (Credit: NFPA 101 Handbook, 2021 edition)   Measuring egress capacity width for a new door leaf that opens 90 degrees (Credit: NFPA 101 Handbook, 2021 edition) Clear width of a door opening is used for meeting minimum door-opening requirements, not for determining egress capacity. In some cases this minimum clear width value is based on the need for occupants traveling in a wheelchair to be able to move the wheelchair through the door opening. The egress capacity width, used to determine how many occupants can be credited with passing through the opening safely, will be less than the actual door leaf width because deductions in width are made for certain encroachments that extends into the door opening. Note: This describes the types of various door width measurements, but users should reference Section 7.2.1.2 of NFPA 101 for further details about how to obtain these measurements in both new and existing conditions. Door Swing Direction Door leaves are required to swing in the direction of egress travel only if any one of the following three conditions exist:   The door serves a room or area with an occupant load of 50 or more,   The door assembly is used in an exit enclosure,  The door opening services a high-hazard contents area.    These three conditions address situations where it is undesirable for an occupant to take time to pull the door open in the direction they are moving from. This could be due to the higher number of occupants, or where conditions exist that could require instant and immediate access to the path of egress travel due to extreme fire or explosion risk.   Ideally, all door leaves in a means of egress would swing in the direction of egress travel. However, because of operational concerns, there are cases where door leaf swing in the direction of egress travel is not desirable. For example, a classroom door leaf that swings into a corridor serving as an exit access for several classrooms might open against another door leaf or against the flow of people and possibly restrict the width available as corridor exit access. The Code recognizes this danger and permits the classroom/corridor door leaf from a room with an occupant load of fewer than 50 persons to swing against the direction of egress travel.  Encroachment To minimize the risk of a door restricting the width available of other egress components, the Code establishes maximum encroachment allowances. During its swing, any door leaf in a means of egress is required to leave not less than one-half of the required width of where it is opening. When the door is fully open, is cannot project more than 7 in (180 mm) into the required width of the aisle, corridor, passage or landing unless the door is equipped with a proper self-closing device and swinging in the direction of egress travel. These two conditions help to ensure that the door leaf does not become an obstruction in the egress path onto which it opens which could reduce capacity and delay egress travel. There are no encroachment limitations for a door opening that provides access to a stair in an existing building. Door leaves capable of swinging a full 180 degrees have a greater utility than door leaves capable of swinging only 90 degrees. The 180-degree-swinging door leaf can be fully opened into a corridor without significant intrusion on corridor width. The 90-degree-swinging door leaf, however, might have to open into an unusually wide corridor, be set into an alcove, or otherwise be recessed so as not to exceed the maximum encroachment. Door leaf swing into a corridor (Credit: NFPA 101 Handbook, 2021 edition)   Door leaf encroachment on landing in new building. (Credit: NFPA 101 Handbook, 2021 edition) Unlatching Force  Several movements are necessary to move a door leaf from its closed to its fully open position. The force needed to unlatch the door assembly cannot exceed 15 lbf (67 N) for hardware that may push pull or slide and 28 in.-lbf for hardware that requires rotation. Additional limits are placed on the force to start the door leaf in motion and on the force necessary to move the door leaf to its required open position. Consideration must be made for persons with severe mobility impairment, such as someone using a wheelchair, who might find it difficult or impossible to exert excessive force to unlatch the door and put it in motion. Additional scenarios may render others incapable of exerting larger forces, so values as high as 50 lbf which were recognized in earlier editions of the Life Safety Code, are now only acceptable for existing installations.     Locking and Latching Doors within an occupant’s means of egress cannot be locked beyond their control but must also be designed to accommodate building’s and occupant needs for security.  If done incorrectly, door locking and latching can become a severe impediment to free and safe egress. The details and permissions for door locking and door latching are extensive, and must not be overlooked. We will address this subject in its entirety in a future blog (stay tuned!)    In conclusion, leaving a building or moving within a building to a point of safety in the event of an emergency is almost guaranteed to include using doors to get there. Proper door operation is critical to occupants being afforded a safe and efficient means of egress. Adequate door opening width, correct door swing direction, minimal encroachment, and appropriate opening and unlatching forces, combined, will work together to provide occupants with reliable and safe door operation.  (Note: Additional details and requirements related to door operation can be found in NFPA 101, Life Safety Code, Section 7.2.1.)
National Wildfire Preparedness Day
Katy, TX building under construction fire

NFPA Addresses Building Under Construction Fires with New Fire Prevention Program Manager Online Training and Webinar Panel on April 15

The National Fire Protection Association (NFPA) launched a new Fire Prevention Program Manager Online Training Series today to help the building industry understand and adopt the strategies defined in NFPA 241 Standard for Safeguarding Construction, Alteration, and Demolition Operation. The topic will also be discussed by a panel of industry experts during an Addressing Fire Safety Challenges During Construction webinar on April 15. Fire Prevention Program Manager Online Training Series In recent weeks, massive building under construction fires have occurred in Las Vegas, NV, Dallas, TX, and Everett, WA, underscoring NFPA research which shows an average of 3,840 fires in structures under construction and 2,580 fires in structures under major renovation per year. Building under construction fires cause an average of four civilian deaths, 49 civilian injuries, and $304 million in direct property damage annually, while fires in buildings undergoing major renovation cause an average of eight civilian deaths, 52 civilian injuries, and $104 million in direct property damage annually. “This new online learning, centered around NFPA 241, was developed in the spirit of the NFPA Fire & Life Safety Ecosystem, which emphasizes the importance of applying referenced standards, investing in safety, and a skilled workforce,” NFPA President and CEO Jim Pauley said.  Although NFPA 241 calls for a fire prevention program manager, credentials for the role are virtually non-existent in the market today. To help construction company leaders, building owners, job site supervisors, code officials, fire marshals, facility managers, and fire protection engineers have the skills needed to ensure the safety of buildings under construction, NFPA developed the new five-hour, five-part online learning series, assessment, and digital badge based on the anticipated job performance requirements (JPRs) for fire prevention program managers proposed for the next edition of NFPA 241. The training covers general fire protection awareness for all people on construction sites and the role of fire prevention program managers on a construction project with an emphasis on: Building safety and fire protection systems Hazard protection Inspections, permits and procedures The NFPA online training series is intended for fire prevention program managers who are new to the role and is designed to help learn how to actively manage a fire prevention program for a typical construction project.  Addressing Fire Safety Challenges During Construction Webinar The NFPA webinar scheduled for April 15 will feature a panel of industry experts discussing key considerations for construction site fire safety, including fire risks and the role of the fire prevention program manager, with time allotted for a robust Q&A session. Webinar panelists providing perspective on the topic include: Jim Begley, PE, FSFPE, CFM, TERPconsulting, principal Matthew Bourque, PE, WS Development, director of Fire Protection and Construction Operations Dick Davis, PE, FM Global, AVP, senior engineering technical specialist Nicholas Dawe, division chief/fire marshal, Cobb County (GA) Fire and Emergency Services
NEC meeting

Celebrating NFPA’s 125th Anniversary and its Rich History with the NEC; Year-Long Anniversary Education Conference Series Kicks Off with One-Day Electrical Program on May 18

NFPA is 125 years young! Founded in 1896 by like-minded visionaries looking to better protect society from the devastating effects of fire, our vital mission has transcended the 10-plus decades that have passed since our we first came to be. Organizations do not reach the age of 125 unless there is a compelling reason to exist. As it was in the beginning, it is still true today. Fire, electrical and other hazards adversely affect our society in many ways. As society evolves so, too, do the hazards we face. While implementation of NFPA codes and standards has ameliorated many hazards, new ones arise and the challenge of making people safer is why NFPA is just as important today as we were 125 years ago. Coincidentally, another group of safety professionals met in March 1896 to take on a parallel challenge. Their task: how to make the burgeoning use of electricity and its associated hazards safe for installations in homes and businesses. Their efforts resulted in the first electrical code that could truly be viewed as a national standard. The first edition of the National Electrical Code (NEC) was published by the National Board of Fire Underwriters in 1897 and standardized electrical safety requirements so that installers, designers, manufacturers, product testing organizations, and inspectors had a single set of installation requirements that could be implemented anywhere. The codification of these standardized rules laid the foundation for the most well-known and widely used construction code in the world. The parallel paths of NFPA and the National Electrical Code intersected in 1911 when NFPA assumed the sponsorship of the National Electrical Code. The Code’s mission perfectly meshed with the NFPA mission and since 1911, 36 subsequent editions of the NEC have been published by NFPA. Like the community that uses it, the NEC is dynamic. The electrical world doesn’t stop and take a breath when each new NEC is published. Advancements in technology and products necessitate the NEC community to always be looking forward, not backwards. Implementation of new technology and methods require an up-to-date installation standard and that is why the process rewinds every three years and starts again. Beginning in November, the over 500 members of the National Electrical Code Committee met to review and act on proposed changes for the 2023 edition. Eighteen technical committees, known in the NEC process as “Code-Making Panels” convened to do the all-important work. These CMP meetings were preceded by countless hours of task group work in preparation for the actual meetings. And, unlike any NEC meeting in the past, the 2023 First Draft meetings had to be held virtually due to the national pandemic.  Despite this changeup in meeting format, the process continued like a well-oiled machine, processing 4,006 public inputs. We invite you to continue to follow the 2023 NEC development process by going to www.nfpa.org/70 and clicking on the “Next Edition” tab. While electrical equipment and wiring practices have changed immeasurably since the first meeting in 1896, the mission of making electrical installations safe remains unchanged. Like the original members of the NEC committee, today’s members approach their task with energy and dedication because they know their work has an outcome that benefits millions. Every receptacle, luminaire, panelboard, and solar photovoltaic panel installed is safety driven by the NEC. While the work is hard, and the hours are long, the men and women of the NEC committee do their work with the satisfaction of knowing they are making a difference. To commemorate its milestone anniversary, and to honor the work of safety professionals around the globe and the impact it has had on the public’s safety, NFPA is rolling out a number of initiatives and events from May 2021 – March 2022, including hosting a 125th Anniversary Conference Series featuring 10 one-day virtual educational programs. On May 18, we are excited to kick it off with the first program of the series: Empowering Electrical Design, Installation, and Safety. The full-day program event is focused on advances in technology, the impact of new technologies on electrical codes and standards, and how technology is influencing today’s industry, with sessions led by leading subject matter experts who are passionate about electrical safety. From in-depth educations sessions to roundtable discussions and networking events, this unique virtual educational program has everything electrical practitioners need to remain competitive in the field and improve safety outcomes on the job. You don’t want to miss this exciting program! Visit our conference series webpage to get all the details and sign up to attend. More information about the full roster of programs happening throughout the year is also available. Not sure you’ll be able to attend? Every program is available on demand to meet your needs and fit your busy schedule. Please visit nfpa.org/conferenceseries to learn about our anniversary celebration and our conference series’ programs. I look forward to seeing you all there!    
1 2 ... 68

Latest Articles