It probably comes as no surprise when we hear people say our world has become increasingly complex with regard to all things electrical. Today, NFPA 70®, National Electrical Code (NEC®) remains the most widely used code in the U.S. and is applied extensively across the globe to safeguard people and property from electrical hazards. It is why the NEC remains the essential resource to ensure all those who work in this field have the latest safety information to address existing and emerging issues. To this end, this year marks the first time that NFPA and Mike Holt Enterprises are partnering together to publish a book explaining the key updates to the next edition of the NEC. The book, Mike Holt’s Illustrated Guide to Changes to the National Electrical Code, 2023 edition, provides colorful graphic depictions of revisions to the NEC to clarify how to apply requirements accurately and explanatory language of how the changes impact electrical industry professionals on the job. It also offers reference information to help provide a deeper understanding of changes and the rationale behind them. NFPA and Mike Holt Enterprises are excited to be working together to advance safety and bring to life this information for those who rely on the NEC to do their jobs. It offers a great opportunity to unite NFPA, the source of the code, and Mike Holt, who is highly recognized for his expertise on the NEC, having devoted his career to understanding the code and sharing his knowledge with others. If you’re a professional electrician, electrical contractor, engineer, or inspector, this book is a valuable resource for understanding the NEC. The book will be available this fall through both Mike Holt Enterprises and NFPA. To pre-order the 2023 NEC, visit the NFPA catalog page.  Stay tuned for more information and visit our electrical solutions page for updates on the book and product offerings. For additional information, read the full news release.

Over the course of 2021, members of NFPA’s Technical Services team developed a collection of blogs on unique subjects related to emerging technologies, the application of common but challenging codes and standards concepts, and the basics of protecting people and buildings from fire and fire protection systems design. As we look back on our efforts of the year, we wanted to share our favorite building fire protection and life safety and fire protection systems blogs from 2021.  Some of these were ones we loved writing, while others were ones you told us you loved reading.  Others made the list because they answer some of the most common questions related to building and life safety and fire protection systems. Whatever the reason for appearing on this list, here is a list of our top blogs of the year: Jonathan Hart PE, Technical Lead, Fire Protection Engineering Weekly Inspections of Electric Fire Pumps Fire pumps are an essential part of many water-based fire protection systems. They are used to increase the pressure (measured in psi or bar) of a water source when that source is not adequate for the system it’s supplying.  The right design, installation, and acceptance testing of these pumps will ensure that they are ready and available to protect the building on the day of the acceptance test. While there is a good deal that goes into a robust ITM program for fire pumps, in this blog, Jonathan Hart, P.E. Technical Lead for Fire Protection Engineering focuses on weekly inspections of fire pumps and what is required. Basics of Suites in Health Care Occupancies The use of suites in health care occupancies can provide significant flexibility in the design, construction, and functional daily use of a space. The term suites can be heard frequently when speaking with health care professionals and often very casually being tossed around. “Is it a suite? Can it be a suite? Have you designated it as a suite?” All of this is with great intentions but can certainly be overwhelming for someone just getting into the field or simply without experience in some more advanced life safety concepts. In terms of NFPA 101® Life Safety Code®, a suite must meet very specific criteria.  Jon discusses the definition of suites, the different types of suites, the benefits of a suite, and the requirements for their application. Shawn Mahoney PE, Engineer Fire Alarm Basics Over the course of the year Shawn Mahoney, P.E., Fire Protection Engineer, wrote a seven-part blog series on fire alarm basics, which serves as an introduction to the many functions and components. The series includes a dive into Initiation, Supervision, Notification, Emergency Control Functions, Power Supplies, and Communication off Premises. Design Requirements for Standpipe Systems Shawn also created a blog describing the different design requirements for each type of standpipe system, which includes a video outlining the procedure that should be taken while hydraulically calculating a standpipe system. Kristin Bigda PE, Technical Lead, Building and Life Safety Egress Design Basics Kristin Bigda, P.E., Technical Lead for Building & Life Safety and Principal Fire Protection Engineer wrote a series of blogs on some of the basics components and concepts when designing a building’s means of egress system.  In this series, topics included swinging-type egress door operation, permitted door locking arrangements, egress stair design, and safely arranging the means of egress. Understanding the fundamentals of designing a means of egress is critical to providing a safe and reliable way out of the building or to a designated point of safety during an emergency. Basics of Fire and Smoke Dampers Heating, ventilating, and air-conditioning systems and other components that support the movement of air throughout buildings are necessary for the day-to-day function of buildings to properly heat, cool and (re)distribute air throughout them.  Dampers protect openings where ducts pass through or terminate in or at fire-rated assemblies in order to maintain the integrity of the assembly and to prevent fire and smoke from spreading to and contaminating other areas of the building that might be otherwise unaffected.  In this blog, Kristin addresses where dampers are required, what standards are applicable, as well as some high-level installation considerations and access and identification of dampers. Valerie Ziavras PE, Engineer Occupancy Classification in the Codes Val Ziavras, P.E, Fire Protection Engineer, discusses how occupancy classification drives the requirements for many different fire and life safety features. These requirements reflect the unique and expected characteristics of the anticipated occupants of that space such as capability of self-preservation, familiarity with the space, age, and alertness. Improperly classifying a building or space risks over- or under-applying necessary code requirements, resulting in buildings lacking fire and life safety features, or containing additional fire and life safety features that are not required by the code. Sprinkler System Basics: Types of Sprinkler Systems Val also wrote about the types of automatic sprinkler systems.  When designing a sprinkler system one of the first decisions a designer has to make is what type of sprinkler system should be installed. Types of sprinkler systems permissible by NFPA 13, Standard for the Installation of Sprinkler Systems, are wet, dry, preaction, and deluge. Other types of extinguishing systems, such as clean agent or water mist, are addressed by other standards. When selecting the appropriate sprinkler system type it is important to first understand the differences between the systems and then to understand how these differences can be beneficial, or detrimental, under certain conditions. Selecting the wrong system type can be costly. Brian O’Connor PE, Engineer Fire Apparatus Access Roads Fire departments provide fire protection services to their jurisdictions as well as respond to a variety of other emergencies such as medical emergencies, motor vehicle accidents, hazardous material spills, electrical hazards, floods, and construction accidents. In order for these first responders to do their jobs effectively they need to be able to have access to the areas where incidents might occur, and this is where fire department access and access road requirements come in.  In this blog, Brian O’Connor, P.E., Fire Protection Engineer highlights the requirements for the location, size and possible obstructions for fire department access roads. Residential Energy Storage System Regulations  An Energy Storage System (ESS)is a technology that helps supplement renewable energy sources (such as wind and solar), support the country’s electrical infrastructure, and can even provide electricity to our homes during a power failure. This technology has a lot of great applications, but it also has inherent fire risks, so it is important to manage risks by taking some basic precautions. This blog by Brian addresses the regulations around how to safely install an ESS in a residential occupancy. Robin Zevotek PE, Principal Engineer Egress Challenges Related to Assembly Spaces Located at the Top of High-Rise Buildings The best views of the urban landscape are often from the top floors of the area's high-rise buildings. This real estate has become sought after for restaurants, multi-purpose rooms, large corporate meeting areas and even tourist attractions. In this blog, Robin discusses how assembly spaces like these, which are located on the top floors of high-rise buildings, combine the hazards of high-occupant density with the egress concerns of high-rise buildings, creating challenges in egress design as well as facility operations. While this list focused mainly on the subject areas of building and life safety and fire protection systems, NFPA’s Technical Services team also represents expertise in electrical safety and emergency response and first responder safety. If you are looking for information on these topics, check out all of the blogs published by NFPA, sign up for NFPA’s personalized e-newsletter (NFPA Network) as well as the following pages: Corey Hannahs, Senior Electrical Content Specialist Dean Austin, Senior Electrical Specialist 2021 was a year like no other and while some of us are glad to see it go, we also recognize that a lot of good came from this year as well. As we look towards the future with fire and life safety in mind, let us know in the comments section below what topics you would like to hear about from us in the upcoming year! 

With the holiday season fast approaching, the presence of combustible decorations, festive lights, and Christmas trees has also arrived.  The presence of additional furnishings and contents, especially dry and unmaintained Christmas trees and other vegetation can contribute significantly to the fuel load of a space and how quickly a fire can develop and spread.   During this time, those responsible for enforcing fire and life safety codes face the challenge of ensuring businesses and residences are following the provisions for furnishings and decorations, as many consumers are unaware of the potential fire safety hazards they could be installing in their facilities and in their homes.  Here we will discuss the requirements for combustible vegetation and both natural and artificial Christmas trees.   Hazards of combustible vegetation and natural cut trees Combustible vegetation can include a variety of items, such as hay bales, limbs, leaves, and Christmas trees. These items, by their nature, are initially fire retardant. The problem arises when they have been cut and packaged, often early in the season, without access to water for extended periods of time. The fire danger of Christmas trees and similar vegetation increases when the tree is not freshly cut and immediately placed in water when purchased. And, the longer they are on display, the increase in potential for the tree to go unwatered and unmaintained.   The best preventive measures for avoiding a dried out tree include using a freshly harvested tree, cutting the butt or bottom end immediately before placing it in water, and checking the water level frequently to ensure that the tree water container is filled. To check the tree itself for dryness, it is best to check a branch near the trunk and allow it to slide between the thumb and forefinger. When needles shed easily, the tree should be removed or replaced, since trees dry from the inside out.  In 2016, students at Worcester Polytechnic Institute constructed a mock living room setup at the fire protection engineering lab at to demonstrate how rapid and intense a dry tree can burn, complete with furniture, rug, curtains, and a decorated Christmas tree. The dry tree was exposed to a flame and within 25 seconds, the branches were fully engulfed and within another 10 seconds, fire had spread to the ceiling and to nearby furnishings. The entire room was thick with fire and smoke, and flashover occurred within 63 seconds. The Fire Research Division at NIST conducted a series of fire experiments to demonstrate how a watered Christmas tree may be less of a fire hazard than a dry one. The Christmas tree that was maintained in a stand that was kept filled with water prior to testing did not ignite when exposed to the same ignition source as the Christmas tree that was not watered.  A slower growing fire can mean more time to react, escape, and notify the fire department and can also reduce the damage done by the fire.  Where are natural Christmas trees permitted? Natural Christmas trees are prohibited or limited in their placement in occupancies that pose special challenges due to the capabilities of occupants, occupant or management control, or the number of occupants. Some exceptions permit live, balled trees, if maintained, and trees in locations where automatic sprinkler systems are installed. Because a living tree needs moisture to stay alive, a balled, living tree should be placed in a container so that the root structure of the tree can be kept moist. (Note: artificial vegetation, including artificial Christmas trees are not limited in their location). Limitations for where natural Christmas trees can be located is as follows:     Limited quantities of other combustible vegetation is permitted in any occupancy if the AHJ determines that adequate safeguards are in place. Adequate safeguards might include sprinkler protection, limited quantities, moisture content, and placement. It is not the intent to consider a Christmas tree “limited quantity of combustible vegetation” where the display of Christmas trees is otherwise prohibited. For example, no natural Christmas tree, cut or balled, is permitted in assembly occupancies. It is not the intent to allow the presence of natural trees if enforced as being a “limited quantity of combustible vegetation”. The requirement for Christmas trees is more restrictive and should prevail.    Other considerations for natural cut trees No means of egress is permitted to be obstructed by any combustible vegetation item or Christmas tree. The preferred location for a Christmas tree from a property owner’s perspective is often in the lobby, the reception area, or a similar area. However, trees located in these areas often encroach on the means of egress and present an increased danger should a fire occur.  When determining where to place combustible vegetation items or Christmas trees, an important consideration is that they might fall over, especially if children or pets come in contact with the tree or vegetation. Placing a portable heater, other heat source, or heating vent near combustible vegetation is prohibited, because the vegetation might tip and also because the heater will likely prematurely dry the vegetation, increasing the risk of a fire.  To maximize the moisture retention of the tree, the bottom end of the trunk should be cut off with a straight cut at least 1⁄2 in. (13 mm) above the end prior to placing the tree in a stand to allow the tree to absorb water. The tree must then be placed in a suitable stand with water and the water level must be maintained above the fresh cut and checked at least once daily. When the tree shows evidence of drying it must be removed from the building immediately.  On the market today are treatments for natural cut Christmas trees that claim to improve the fire performance of the tree. However, the use of untested fire retardant treatments may actually increase the rate at which the tree dries out and can contribute to the rapid growth of a fire.  Where fire retardant treatments are applied to natural cut Christmas trees (the treatments are not required), the fire-retardant treatment (not the tree) is required to comply with both Test Method 1 and Test Method 2 of ASTM E3082, Standard Test Methods for Determining the Effectiveness of Fire Retardant Treatments for Natural Christmas Trees.  This standard provides a two-step testing process for determining the effectiveness of surface applied treatments for natural Christmas trees to improve fire test response. In order for a treatment to be considered compliant with ASTM E3082, the passing criteria of both Methods 1 and 2 as prescribed in the standard are to be met. Artificial vegetation including Christmas trees  There are no limitations on what occupancies permit the use of artificial Christmas trees so it’s important that their potential contribution to fire development and flammability be controlled.  Combustible artificial decorative vegetation and artificial Christmas trees must now meet the appropriate fire test criteria. This includes requirements for compliance with either the flame propagation performance criteria of Test Method 1 or Test Method 2, as appropriate, of NFPA 701 or a maximum heat release rate of 100 kW when tested to NFPA 289, using the 20 kW ignition source. NFPA 701, Standard Methods of Fire Tests for Flame Propagation of Textiles and Films, establishes test methods to assess the propagation of flame of various textiles and films under specified fire test conditions. NFPA 289, Standard Method of Fire Test for Individual Fuel Packages, describes a fire test method for determining the fire test response characteristics of individual fuel packages in a room when exposed to various ignition sources in a controlled environment.  Each individual artificial decorative vegetation item (Christmas tree) must be labeled, in an approved manner, to demonstrate compliance with one of the fire test options noted above. Additional requirements for Christmas trees Another hazard associated with Christmas trees is the decorative lighting. Electrical wiring and listed luminaires and lighting used on combustible artificial or natural Christmas trees must be listed for that particular application. The listing will also dictate whether the lights have been tested for indoor and/or outdoor use. In addition to the listing requirement, lighting should also be checked for wear and tear and damages. Worn or damaged wiring and loose bulbs may present unsafe conditions.  Electrical lights shall be prohibited on metal artificial trees. Candles and open flames cannot be not be used on or near combustible artificial or natural decorative vegetation and Christmas trees.   Looking for more information? Requirements for artificial and natural Christmas trees and other vegetation can be found in both NFPA 1, Fire Code, Chapter 12 as well as NFPA 101, Life Safety Code, Chapter 10.  The 2021 editions of both Codes were updates to include the specific fire test requirements as well as other clarifications for how to safely include Christmas trees in your business or residence.    NFPA also offers many additional resources on holiday safety, including a Christmas Tree Safety Tip Sheet and information on Christmas tree and decoration fires.  All holiday safety information can be found here. 

Buildings must be designed so that exits are always readily accessible and access to those exits is arranged so that they can be reached at all times. To do this, there are some fundamental design concepts to follow to ensure that the means of egress is arranged for an exit to be reached by occupants in a safe and efficient manner. Means of egress design must consider the distance occupants travel to an exit, how far apart exits are located from one another, and the arrangement of the paths of travel within the means of egress. Referenced in this blog are design requirements for exits, exit accesses and exit discharge paths. As a reminder, the means of egress is made up of three parts: the exit access, the exit and the exit discharge. Exit access includes all travel within occupied areas of the building leading up to an exit. Exits are those portions of the means of egress that are separated from other building spaces protecting the space from the effects of fire, such as an enclosed exit stair or a door to the outside. Exit discharge is the travel leading from the exit to the public way (designated and approved point of safety.) What is travel distance? Travel distance is the maximum permitted distance that occupants are permitted to travel from their location in a building to the nearest exit. Although more than one exit might be required, the travel distance to exits other than the closest exit is not regulated. Excessive travel distances can be hazardous because they increase the time required by occupants to reach the safety of an exit, whether the exit is a door directly to the outside or into an enclosed exit stair from an upper floor of a building. The maximum allowed travel distances are based on factors that include demographics, potential obstructions in the path of travel, number of people in any room or space and the distance to the nearest door opening, the amount and nature of expected combustibles and the speed that fire might spread in that space. Allowable travel distances vary with the type and size of occupancy and the degree of hazard present. For most occupancies, the allowable travel distance can be increased if the building is protected throughout by automatic sprinkler systems. Travel distance is measured on the floor or other walking surface along the centerline of the natural path of travel, starting from the most remote point subject to occupancy, curving around any corners or obstructions and ends at the center of the doorway or other point at which the exit begins. Where there are stairs included as a component of exit access rather than an exit, the travel over those stairs is included in the travel distance measurement. The natural path of travel is influenced by the contents and occupancy of the building, and a designer should not assume a straight-line measurement for travel distance. Furniture, fixtures, machinery, or storage found in the path of travel can increase the length of travel distance. What is common path of travel? It is ideal to always be able to move in different directions from any location, to allow different paths of travel to different exits. However, typical floor layouts and furnishing arrangements often create spaces where travel in a single direction is necessary for a limited distance before it becomes possible to travel in different directions. A common path of travel exists in the initial portion of the exit access where a space is arranged so that occupants within that space can travel in only one direction to reach any of the exits or to reach the point at which they have the choice of two paths of travel to two different remote exits. When an occupant is provided only one direction before reaching a point at which travel in independent direction, all that travel is considered common path. Common path of travel might exist only within rooms and occupied spaces, or it might exist within the combination of room space and corridors, depending on where the point is that two different options to go to two different exits is offered. Travel within rooms or areas with only one door is all considered common. Like travel distance, maximum permitted common path of travel distances are regulated by the specific occupant chapter. The overall preference in building design is to reduce common path of travel, so the permitted values are not very high. Where occupants are able to travel in only one direction towards an exit, the risk of a fire impacting that egress path and access to exits increases. Common path is permitted only where the risk is reduced by other fire protection features as well as a low risk in the specific scenario. Common paths of travel and dead-end corridors (explained below) are measured using the same principles used to measure travel distance. What is a dead end (corridor)? The terms dead end and common path of travel are commonly used interchangeably and while the concepts of each are similar in practice, they are two different concepts. While a dead end is similar to a common path of travel, a dead end can exist in a path of travel where there is no direct access from an occupied space but can also exist where an occupant enters a corridor thinking there is an exit at the end and, finding none, is forced to retrace their path to reach a choice of exits. Although relatively short dead-end corridors are permitted for all occupancies, it is a better practice to avoid them as dead-end corridors increase the danger of people becoming trapped during a fire as well as increase the travel time to reaching an exit. Two common types of dead ends in corridors include corridor space beyond an exit, where an occupant moving toward the exit off the corridor mistakenly travels past it into the dead end and also space created by the elevator lobby that does not contain an exit. Remoteness It is a principle of life safety in buildings that if multiple exits (as well as exit accesses and exit discharges) are required, they need to be not only separate but also remote from one another and be arranged to minimize the possibility that more than one has the potential to be blocked by any one fire or other emergency condition. Although the objective of this requirement is clear, the term ‘remote’ cannot always be clearly defined. To be considered remote, the exits, exit accesses and exit discharges in new buildings must be located at a distance from one another not less than one-half (one-third if the building is fully sprinklered) the length of the maximum overall diagonal dimension of the building or area to be served, measured in a straight line between the nearest edge of the exits, exit accesses, or exit discharges. Where exits are located at each end of a long corridor or at each end or side of a building, they qualify as remotely located exits. However, core-type buildings with elevators, service shafts, and stairs in one central or side core introduce some challenging problems with respect to exit remoteness. Other ways of measuring remoteness, utilizing corridors with 1-hour fire separation, also exist. For buildings that are not high-rise, the distance between exit enclosures can be measured along a corridor with a minimum 1-hour separation. In this scenario, although the exit enclosures are physically closer to each other than the dimension measured along the corridor, the exits will perform, under fire conditions, as if they were the corridor length apart. Conclusion Proper arrangement of the means of egress ensures that exits are made available to occupants at all times and are located in the building where they can be accessed without traveling too far, for too long, or with the risk of the exits being compromised during an emergency. For more details on the arrangement of the means of egress concepts addressed in this blog as well as additional requirements see NFPA 101®, Life Safety Code®, Sections 7.5 and 7.6.

For many of us, walking up and down stairs is a routine part of our day. We may use stairs at work, at entertainment venues, and in our home without thinking twice about how their design and function contribute greatly to life safety in both emergency and non-emergency situations. Recently, I wrote about the details and the importance of handrail design for safe and efficient stair use. Here I will focus on other details of stair design including riser height, tread depth, stair width, stair landings, and construction uniformity that are mandated in order to create a safe path of travel when using the stairs to move throughout the building. These standard stair design details are mandated for egress stairs in the exit access, exits and exit discharge. (Where you have other than standard stairs such as curved stairs, spiral stairs or winders within a means of egress, consult NFPA 101, Life Safety Code, Chapter 7 for further details on their design.) Construction All stairs serving as required means of egress must be of permanent fixed construction (unless they are stairs serving seating that is designed to be repositioned, such as those in theaters, for example, where seating sections are added, removed, or relocated and it is impractical for stairs associated with that seating to be of fixed, permanent construction). In buildings required by NFPA 101, Life Safety Code, to be of Type I or Type II construction, each stair, platform, and landing, not including handrails and existing stairs, are required to be of noncombustible material throughout. Stairs can be of combustible construction if the building is not required by that occupancy to be of Type I or Type II construction. For example, an occupancy might not have any requirements related to minimum building construction type, or the occupancy chapter might permit Type III, Type IV, or Type V construction. If the building is required to be of Type I or Type II construction, the materials used for new stair construction (stairs, platforms, and landings) must be noncombustible. Dimensional Criteria and Uniformity Providing adequate width is one of the most important features of egress stair design as the width ensures that the stairs can accommodate enough people safely and efficiently during an evacuation.  Providing appropriate stair riser height and tread depth ensures that stairs are safe, usable, and presents tripping and discomfort when traveling up or down the stairs.  The minimum required width as well as other dimensional criteria for both new and existing stairs is summarized in the tables below (reference: Chapter 7 of NFPA 101).  It should be noted that in some cases, the egress capacity will require a stair to have a greater width than the minimum specified here. The minimum width of new stairs is 36 in. (915 mm) where the total occupant load of all stories served by the stair is fewer than 50. Where new stairs serve a total cumulative occupant load (assigned to that stair) of 50 or more people but less than 2000 people the minimum width is 44 in. (1120 mm) and where the total cumulative occupant load assigned to the stair is greater than or equal to 2000 people the minimum width is 56 in. (1420 mm).  Riser height is measured as the vertical distance between tread nosings. Tread depth is measured horizontally, between the vertical planes of the leading projection of adjacent treads and at a right angle to the tread’s leading edge. Measuring both riser height and tread depth needs to represent the actual space available to those using the stairs. It cannot include any part of the tread that is not available for someone to place their foot.  Installing floor coverings to existing stairs might also reduce the available space for use on the stairs. Irregularities in stair geometry, either from one step to the next or over an entire run of stairs, can cause accidents, tripping and falling when using the stairs. When many people are using the stair at once, just one accident can cause delays and disruptions in movement and use of the stairs, and increase the overall time of evacuation. There should be no design irregularities. Very small variations due to construction are permitted between adjacent treads and risers and the overall different over the entire flight of stairs. The variation between the sizes of the largest and smallest riser or between the largest and smallest tread depths shall not exceed 3∕ 8 in. (9.5 mm) in any flight. Stair Landings As a general rule, stairs must have landings at door openings because it is unsafe to move through a door opening and immediately begin vertical travel on a stair. In existing buildings, a door assembly at the top of a stair is permitted to open directly to the stair, without first providing a level landing, provided that the door leaf does not swing over the stair (rather, it swings away from the stair) and the door opening serves an area with an occupant load of fewer than 50 people. Stairs and intermediate landings must continue with no decrease in width along the direction of egress travel. A reduction in width of a stair landing could reduce the overall capacity of the stair.  In new buildings, every landing will have a dimension, measured in the direction of travel, that is not less than the width of the stair. Landings are not required to exceed 48 in. (1220 mm) in the direction of travel, provided that the stair has a straight run. Intermediate stair landings serve as effective breaks in runs of stairs, which allow persons who slip or trip to halt their fall.     Stair Tread and Stair Landing Surfaces Surface Stair treads and landings must be solid, without perforations, except for noncombustible grated stair treads and landings as otherwise provided in the following occupancies: assembly, detention and correctional, industrial and storage. Solid treads and solid landing floors provide a visual barrier that shields the user’s view of the vertical drop beneath the stair. People with a fear of high places are more comfortable using these stairs. Grated and expanded metal treads and landings could catch the heel of a shoe and present a tripping hazard. Noncombustible, grated stair treads are permitted in areas not accessed by the general public, such as catwalks and gridirons in theaters, resident housing areas in prisons, factories and other industrial occupancies, and storage occupancies. Projections Stair treads and landings must also be free of projections or lips that could trip stair users. The tripping hazard occurs especially when someone is traveling down the stairs, where the tread walking surface has projections. The installation of a surface-mounted stair nosing or a strip of material onto an existing stair tread might produce a projection that creates a tripping hazard. Tread nosings that project over adjacent treads can also be a tripping hazard. (Additional considerations for minimizing tripping hazards for accessibility is also addressed in ICC A117.1, Accessible and Usable Buildings and Facilities.) Traction Stair treads and landings within the same stairway must have consistent surface traction. This means that slip resistance is reasonably uniform and sufficient to minimize risk of slipping across the treads. Consistency is important because misleading a person’s expectation of the surface they will be walking on is a major factor in missteps and falls involving slipping. Materials used for floors that are acceptable as slip resistant generally provide adequate slip resistance where used for stair treads. If stair treads are wet, there is also increased danger of slipping, just as there is an increased danger of slipping on wet floors of similar materials. The many details of stair design may seem minute and unimportant in the overall picture of fire and life safety, but stairs can be dangerous and an impediment to egress if not designed correctly.  Tripping, falling, and a lack of confidence by those using egress stairs can interrupt efficient egress travel and building evacuation.  Paying careful attention to stair design will greatly contribute to occupant safety during both day to day and emergency conditions

Editor's note: NFPA has developed a new fact sheet on the basics of fire and smoke dampers. Download it now! Heating, ventilating, and air-conditioning systems and other components that support the movement of air throughout buildings are necessary for the day-to-day function of buildings in order to properly heat, cool and (re)distribute air throughout them. Air is distributed in air-conditioning and ventilating systems by ducts and plenums and for the system to reach everywhere it needs to within the building, it may require penetrating fire-resistance rated assemblies or assemblies protected against the transfer of smoke. Like fire doors protecting openings in fire-resistance rated construction, dampers also protect openings where ducts pass through or terminate in or at fire rated assemblies in order to maintain the integrity of the assembly and to prevent fire and smoke from spreading to and contaminating other areas of the building that might be otherwise unaffected. During a fire, the air distribution system may transport deadly smoke and products of combustion instead of breathable air. If proper design and installation precautions are not taken, smoke, fire gases, heat, and even flame can spread throughout the area served by the duct system. Improper plenum locations, lack of detection equipment in the system, and lack of required fire and smoke dampers in appropriate walls, ceilings, or partitions can lead to tragic situations. What are fire and smoke dampers and where are they installed?  Fire dampers are installed in ducts passing through or in air outlet openings terminating at shaft walls, fire barriers (such as an occupancy separation wall, horizontal exit walls, corridor walls, corridor ceilings, floor-ceiling assemblies) and other fire resistance–rated assemblies as required by a building or life safety code and other applicable standards.  Under severe fire exposure, a duct may eventually collapse or significantly deform, creating an opening in the fire barrier. Fire dampers provide a method of protecting such penetrations and openings.   A fire damper is designed to, and required to, close automatically upon detection of heat (such as a fusible link or heat detector) and to interrupt airflow and to restrict the passage of flame.  Fire dampers are required to close against the maximum calculated airflow of that portion of the system in which they are installed. Those that are intended to close under airflow are labeled for use in Dynamic Systems (A dynamic systems is an HVAC system designed to maintain the movement of air within the system at the indication of a fire); those that are intended to close after airflow has stopped by automatically shutting down the fan or airflow in the event of a fire are labeled for use in Static Systems (a static system is an HVAC system designed to stop the movement of air within the system at the indication of a fire). Fire dampers are provided with an hourly fire rating.    Smoke damper’s primary function is to control the movement of smoke in dynamic air distribution systems, and they reduce the possibility of smoke transfer within ductwork or through wall openings. They are installed in ducts passing through, or air outlet openings terminating at, smoke barriers, shaft walls, horizontal exit walls, corridor walls, corridor ceilings, and other barriers designed to resist the spread of smoke as required by a building or life safety code and other applicable standards. Smoke dampers operate automatically on detection of smoke and must function so that smoke movement through the duct is halted.  Their activation can be by area detectors that are installed in the related smoke compartment or by detectors that are installed in the air duct systems. Smoke dampers are provided with leakage and temperature ratings.   A combination fire/smoke damper is used when a barrier is both rated for fire resistance as well as designed to restrict the transfer of smoke and will meet both the fire damper and smoke damper requirements.   What standards area applicable?  Multiples codes and standards are applicable to the installation of fire and smoke dampers.  Knowing what each document addresses can help map out the provisions for a safe and successful damper installation.  It is suggested that these documents be reviewed for further details beyond the summary that is provided here.  NFPA 101®, Life Safety Code® mandates where smoke dampers are required as well as their ratings, access and identification requirements, and activation requirements. Smoke dampers are required in air-transfer openings (an opening designed to allow the movement of environmental air between two contiguous spaces) in smoke partitions and in air transfer openings and duct penetrations in smoke barriers.  Where a smoke barrier is also constructed as a fire barrier, a combination fire/smoke damper must be used.  There are multiple exemptions where smoke dampers may not be required in smoke barriers such as where ducts or air-transfer openings are part of an engineered smoke control system and that smoke damper will interfere with the operation of a smoke control system or where ducts penetrate floors that serve as smoke barriers. NFPA 5000®, Building Construction and Safety Code® mandates where fire dampers are required and their required ratings as well as access and identification requirements for fire and smoke dampers. Fire dampers are required in the following locations:  Ducts and air-transfer openings penetrating walls or partitions having a fire resistance rating of 2 or more hours, Ducts and air-transfer openings penetrating shaft walls having a fire resistance rating of 1 or more hours, Ducts and air-transfer openings penetrating floors that are required to have protected openings where the duct also is not protected by a shaft enclosure, Air-transfer openings that occur in walls or partitions that are required to have a fire resistance rating of 30 minutes or more.   NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems also mandates additional locations where fire and smoke dampers are required, working in conjunction with the building code and life safety codes. In addition, it mandates the minimum required rating of the fire damper based on its location.  Compliance with NFPA 90A is mandated by NFPA 101, NFPA 5000 and NFPA 80.  NFPA 80, Standard for Fire Doors and Other Opening Protectives and NFPA 105, Standard for Smoke Door Assemblies and Other Opening Protectives apply after it has been determined where a damper is required and how to access and identify it.  Users are directed to NFPA 80 and NFPA 105 for additional installation details as well as all requirements for the inspections, testing, and maintenance of the dampers. NFPA 80 covers fire dampers as well as combination fire/smoke dampers and NFPA 105 addresses smoke dampers.  Fire dampers are tested and listed for use in air-conditioning and ventilating ducts by UL in accordance with UL 555, Fire Dampers. These dampers include single-blade, multiblade, and interlocking-blade types, all actuated by fusible links. Smoke dampers require compliance with UL 555S, Smoke Dampers.  Combination fire and smoke dampers will meet the applicable requirements of both UL 555 and UL 555S       Fire and Smoke Damper Installation  First and foremost, dampers must be installed in accordance with the manufacturer’s installation instructions and in accordance with their listing. For new installations, retaining the installation instructions on site can help verify that a damper has been properly installed.     Access to both fire and smoke dampers is required for inspection, testing, and maintenance. Smoke and combination fire and smoke dampers in new construction must be provided with an approved means of access large enough to allow inspection and maintenance of the damper and its operating parts.  Access cannot affect the integrity, continuity, or rating of the assembly where its located and must also comply with any access requirements in the mechanical code. Access points must also be provided with permanent identification indicating the type of damper (fire damper, smoke damper, fire/smoke damper). In some situations, where space constraints or physical barriers in new construction restrict access to a damper for periodic inspection and testing, the damper is required to be a single- or multi-blade-type damper and must comply with remote inspection requirements (found in NFPA 80 or NFPA 105.)   After a damper has been installed, an operational test much be completed. This test ensures that the damper has been installed correctly within the air distribution system, is fully functional, closes completely without obstructions and contains all the correct components and devices as part of its assembly. The operational test may be required be conducted under normal HVAC airflow and non-airflow conditions. The damper shall fully close under both test conditions.   Conclusion  Both fire and smoke dampers are important building and life safety equipment that protect people and buildings from the effects of fire. It is critical that they are installed, and accessible, where required throughout buildings and installed properly so that they will operate when required under fire conditions. Without them, fire and smoke could travel throughout the building to spaces otherwise untouched by the fire. Check back for future blogs where we will address the requirements, both in-person and remote, for inspection, testing and maintenance of fire and smoke dampers.  For more information on fire and smoke dampers as well as other opening protectives, you can check also out our various training offerings here.