AUTHOR: Brian O'Connor

Commodity Classifications in NFPA 13

Commodity classifications are used to categorize the contents of storage occupancies so that the appropriate sprinkler system design can be identified. Commodity classifications are determined by not only the product but also the packaging of that product, the container those packaged products are in, and even the pallet type. This can get a little complicated, so I’ll run through a quick example. We have glass jars stored in a double layered carboard box with cardboard dividers and it is sitting on a reinforced plastic pallet. Even though the glass jars are only a Class I commodity, the cardboard box and plastic pallet increases the fuel load so that it should be considered a Class IV. Commodity Classifications are broken down into Classes I through IV and Group A though C plastics with Class I being the lowest hazard level and Group A expanded plastics being the highest hazard level. Class I: A Class I commodity is defined as a noncombustible product that meets one of the following criteria: Placed directly on wood pallets Placed in single-layer corrugated cardboard boxes, with or without single-thickness cardboard dividers Shrink-wrapped or paper-wrapped as a unit load Class II: A Class II commodity is defined as a noncombustible product that is in slatted wooden crates, solid wood boxes, multiple-layered corrugated cardboard box, or equivalent combustible packaging material. Class III: A Class III commodity is defined as a product fashioned from wood, paper, natural fibers, or Group C plastics with or without cartons, boxes, or crates. A Class III commodity shall be permitted to contain a limited amount (5 percent or less by weight of nonexpanded plastic or 5 percent or less by volume of expanded plastic) of Group A or Group B plastics. Class IV: A Class IV commodity is defined as a product that meets one of the following criteria: Constructed partially or totally of Group B plastics Consists of free-flowing Group A plastic materials Cartoned, or within a wooden container, that contains greater than 5 percent and up to 15 percent by weight of Group A nonexpanded plastic Cartoned, or within a wooden container, that contains greater than 5 percent and up to 25 percent by volume of expanded Group A plastics Cartoned, or within a wooden container, that contains a mix of Group A expanded and nonexpanded plastics and complies with the graph section at the end of the blog Exposed, that contains greater than 5 percent and up to 15 percent by weight of Group A nonexpanded plastic Exposed, that contains a mix of Group A expanded and nonexpanded plastics and complies with the graph section at the end of the blog PLASTICS Plastics are a little more straightforward since there is a specific list of what each group contains. Classifying plastics gets complicated when the commodity being stored is a combination of different groups of plastics, but the graphs at the end of this blog should be able to help alleviate some of that work. Group C Plastics: Group C plastics are treated as Class III Commodities and consist of the following: Fluoroplastics (PCTFE — polychlorotrifluoroethylene; PTFE — polytetrafluoroethylene) Melamine (melamine formaldehyde) Phenolic PVC (polyvinyl chloride — flexible — PVCs with plasticizer content up to 20 percent) PVDC (polyvinylidene chloride) PVDF (polyvinylidene fluoride) Urea (urea formaldehyde) Group B Plastics: Group B plastics are treated as Class IV Commodities and consist of the following: Chloroprene rubber Fluoroplastics (ECTFE — ethylene-chlorotrifluoro-ethylene copolymer; ETFE — ethylene-tetrafluoroethylene-copolymer; FEP — fluorinated ethylene-propylene copolymer) Silicone rubber Group A Plastic: Group A plastics are further subdivided into expanded and nonexpanded Group A plastics and consist of all of the plastics listed in the table below. ABS (acrylonitrile-butadiene-styrene copolymer) FRP (fiberglass-reinforced polyester) Polycarbonate PVC (polyvinyl chloride — highly plasticized, with plasticizer content greater than 20 percent) (rarely found) Acetal (polyformaldehyde) Natural rubber Polyester elastomer Acrylic (polymethyl methacrylate) Nitrile-rubber (acrylonitrile-butadiene-rubber) Polyethylene Butyl rubber Nylon (nylon 6, nylon 6/6) Polypropylene PVF (polyvinyl fluoride) Cellulosics (cellulose acetate, cellulose acetate butyrate, ethyl cellulose) PET (thermoplastic polyester) Polystyrene SAN (styrene acrylonitrile) EPDM (ethylene-propylene rubber) Polybutadiene Polyurethane SBR (styrene-butadiene rubber) HELPFUL DEFINITIONS One of the biggest issues I see when people are starting to learn about sprinkler design for storage occupancies is that they don’t know the terminology. It is important to fully understand the definitions for the terms used in the storage chapters of NFPA 13, Standard for the Installation of Sprinkler Systems. I recommend looking at the definition chapter of NFPA 13 to make sure you understand exactly what a term means because oftentimes it means something different than what you would expect. Here are a couple of definitions that are important to understanding this blog. Expanded Group A Plastics: Those plastics, the density of which is reduced by the presence of air pockets dispersed throughout their mass. Some examples include packing peanuts or acoustic foam. Nonexpanded is everything else that is not covered under the definition of expanded. Free Flowing Group A Plastics (protect as Class IV): Those plastics that fall out of their containers during a fire, fill flue spaces, and create a smothering effect on the fire. Examples include powder, pellets, flakes or random-packed small objects. Free flowing plastics are those small objects that fill a box or a subdivision within the box without restraint. The theory is that during a fire. The objects will freely fall out of the box and either smother the fire or fall away from it, removing themselves as fuel. Since the burning rate is reduced and fuel load has been lessened, free-flowing plastics are permitted to be treated as a Class IV commodity. Exposed: Commodities not in packaging or coverings that absorb water. For example, a cardboard box or wooden container can both absorb water so they would not be considered exposed. However, something that is wrapped in plastic sheeting could be considered exposed since plastic sheeting doesn’t absorb water. Cartoned - A method of storage consisting of corrugated cardboard or paperboard containers fully enclosing the commodity. GRAPHS The following tables come from NFPA 13 to help with navigating how a commodity should be classified when it contains Group A plastics. Note that the X axis is percentage by volume while the Y axis is percentage be weight.  The first graph addresses exposed commodities while the second graph addresses commodities that are cartoned or within a wooden container (non-exposed). PALLETS When commodities are tested, they are tested on wooden pallets. This means that wooden pallets are assumed to be used in commodity classifications, however if plastic pallets are used, they increase the commodity classification by two classes. Although, if the plastic pallet is made of polypropylene or high-density polyethylene and marked as “nonreinforced” then the commodity classification only needs to be increased by one classification. Plastic Pallet Increase (+2) Class I --> Class III Class II --> Class IV Class III --> Group A Plastics Class IV --> Cartoned nonexpanded Group A plastic Group A Plastics --> Group A Plastics (No increase)  Unreinforced Polypropylene or High-Density Polyethylene Plastic Pallet Increase (+1) Class I --> Class II Class II --> Class III Class III --> Class IV Class IV --> Cartoned nonexpanded Group A plastic Group A Plastics --> Group A Plastics (No increase) Determining the classification for commodities in storage occupancies can get complicated at times but I can not stress how important of a step this is during the sprinkler design process. It is also imperative that the owner understands what the building is designed to handle as well as what can and can not be stored in the facility once it is built. I hope you enjoyed the blog. Comment below if you have questions and be sure to share this with friends and colleagues who might find it helpful.
Energy Storage System

Battery Energy Storage Hazards and Failure Modes

Around the globe energy storage systems are being installed at an unprecedented rate, and for good reasons. There are a lot of benefits that energy storage systems (ESS) can provide, but along with those benefits come some hazards that need to be considered. This blog will talk about a handful of hazards that are unique to energy storage systems as well as the failure modes that can lead to those hazards. While there are many different types of energy storage systems in existence, this blog will focus on the lithium-ion family of battery energy storage systems. The size of a battery ESS can also vary greatly but these hazards and failure modes apply to all battery ESS regardless of size. HAZARDS As with most electrical equipment there are common hazards that need to be addressed as part of operation and maintenance such as a potential for electrical shock and arc flash. These should always be accounted for when working in and around energy storage systems. More information on how to work with electrical equipment safely can be found in NFPA 70E, Standard for Electrical Safety in the Workplace. Thermal Runaway – Thermal runaway is the uncontrollable self-heating of a battery cell. It begins when the heat generated within a battery exceeds the amount of heat that can be dissipated to its surroundings. The initial overheated cell then generates flammable and toxic gasses and can reach a heat high enough to ignite those gasses. This phenomenon can cascade to adjacent cells and progress through the ESS, thus the term “runaway”. Off Gassing – The gasses that ae released from battery energy storage systems are highly flammable and toxic. The type of gas released depends on the battery chemistry involved but typically includes gases such as: carbon monoxide, carbon dioxide, hydrogen, methane, ethane, and other hydrocarbons. If the gas is able to reach it’s lower explosive limit before finding an ignition source then there is the potential for an explosion. An example of this occurred in Surprise, Arizona back in 2019. Stranded Energy – Standard energy is the term used for when a battery has no safe way of discharging its stored energy. This commonly occurs after an ESS fire has been extinguished and the battery terminals have been damaged. This is a shock hazard to those working with the damaged ESS since it still contains an unknown amount of electrical energy. Stranded energy can also lead to reignition of a fire within minute, hours, or even days after the initial event. FAILURE MODES There are several ways in which batteries can fail, often resulting in fires, explosions and/or the release of toxic gases. Thermal Abuse – Energy storage systems have a set range of temperatures in which they are designed to operate, which is usually provided by the manufacturer. If operating outside an acceptable temperature range, the ESS may not work as intended, may result in premature aging of the battery, and can even cause a complete failure that can lead to fire and explosions. Thermal abuse is caused by external sources, it is the result of contact with burning or overheated adjacent cells, elevated temperatures, or exposure to other external heat sources associated with both storage of the cells or the environment in which the ESS is installed. Electrical Abuse – Electrical abuse takes place when a battery is overcharged, charged too rapidly, or externally short-circuited. This can also occur if the battery is discharged too rapidly or if the battery is over discharged below its specified end voltage. Electrical abuse can lead to an inoperable ESS, overheating, fire, and explosion. Mechanical Abuse – Mechanical abuse occurs if the battery is physically compromised when the battery is crushed, dropped, penetrated, or otherwise distorted to failure by mechanical force. Internal Faults – Internal faults can result from inadequate design, the use of low-quality materials, or deficiencies in the manufacturing process. It might be worth noting that the failure rate for lithium-ion cells is said to be on the order of one in a million. Environmental Impacts – Environmental impacts can lead to battery failure. This can be the result of ambient temperature extremes, seismic activity, floods, ingress of debris or corrosive mists such as dust (deserts) or salt fog (marine locations), or rodent damage to wiring.  Some locations subjected to rapid temperature variations such as in the mountains can experience dewing leading to damage within the ESS located outdoors if not well-controlled. While there are numerous applications and advantages to using battery energy storage systems it is important to keep in mind that there are hazards associated with these installations. Understanding the hazards and what leads to those hazards is just the first step in protecting against them. Strategies to mitigate these hazards and failure modes can be found in NFPA 855, Standard for the installation of Energy Storage Systems. NFPA also has a number of other energy storage system resources including the following: Fact sheet on ESS PV and ESS training ESS resource page Blog on residential ESS
Man in a warehouse

Unique Fire Protection Challenges Found in Warehouse/Distribution Centers

NFPA research shows that warehouse fires happen at a frequent rate with an average of 1,410 warehouse fires, two deaths, 20 injuries, and an estimated $159.4 million in direct property damage annually. To avoid becoming part of these statistics it is essential that a fire protection system is correctly designed, installed, inspected, maintained, and tested. Warehouse environments require additional considerations for sprinkler system design. This is due to the nature of how warehouses are designed and used. This blog will look at a handful of unique fire protection challenges found in warehouses and other distribution centers. For more specific information on how to design a sprinkler system see NFPA 13, Standard for the Installation of Sprinkler Systems. Commodity classification The most obvious unique characteristic of a warehouse is that the purpose of the building is to store a large number of goods and products. This can increase the fire load by a significant amount. This is why it is essential, when designing an automatic sprinkler system for a warehouse, that the items being stored are assigned the proper commodity classification. When determining the commodity classification, it is important to include not only the product itself but also the packing material as well as the container and pallet. The different commodity classifications are as follows: Class I – a noncombustible product that is either stored in single layer cardboard boxes or shrink wrapped or paper wrapped. The product can either be stored with or without wooden pallets. Class II – A noncombustible product stored in either wooden crates or multiple-layered cardboard boxes. The product can either be stored with or without wooden pallets. Class III – A product made from wood, paper, natural fibers, or Group C plastics. This can be stored with or without wooden crates and pallets. Class IV – A product that can be made from a mixture of Group B plastics with wood, paper, natural fibers or Class C plastics. The product is allowed to be made from a small percentage of Group A Plastics Group C Plastic – Certain plastics such as PVC. This is treated the same as a Class III Commodity Group B Plastic – Certain plastic rubbers such as silicone. This is treated the same as a Class IV commodity. Group A Plastic -   The most flammable plastics and natural rubbers. This group is further subdivided into expanded or nonexpanded plastics. This is treated differently from all other commodity classifications. In rack sprinklers Warehouses are the only location where you will find sprinklers both at the ceiling level as well as in racks closer to ground level. This is a unique way to get water in the racks and applied to a fire before it is able to grow beyond the capabilities of the sprinkler system. Some higher hazard commodities will require in-rack sprinklers while other commodities have the option to include rack sprinklers and decrease the robustness of the ceiling sprinklers. Prewetting Most sprinkler systems rely on the concept of prewetting as a critical component in controlling a developing fire. Prewetting is when the sprinkler system activates and wets the fuel in front of the fires path, slowing down the fire growth. The issue with warehouses is that they can contain encapsulated products, which are impervious to prewetting (think of something that is wrapped in plastic on all sides). Due to this challenge the sprinkler system would have to be designed to be robust enough to be able to control a fire without prewetting. Obstructions In warehouses there is the potential for Early Suppression Fast Response (ESFR) sprinklers to be used. ESFR sprinklers rely on getting water to the fire quickly, this means both activating earlier than normal sprinklers and discharging water at a higher velocity. Because of this unique design feature, it makes it even more important to ensure that these sprinklers are clear of obstructions. If the sprinklers were prevented from reaching the fire during the early stages of fire growth the sprinkler could be ineffective. Change management Warehouses are likely to have items with varying commodity classifications being stored. Sprinkler design can account for this by either designing to the highest hazard commodity or by creating separate zones for higher and lower hazard commodities. Either way, when warehouses change what they are storing it is essential that the new products do not exceed the hazard level that the sprinklers were designed for. Flammable liquids and gasses Another unique fire protection challenge for warehouses is that there might be large quantities of hazardous materials such as flammable liquids and gasses. These types of materials typically fall outside of the scope of NFPA 13 and into other NFPA documents such as NFPA 30, Flammable and Combustible Liquids Code, NFPA 55, Compressed Gases and Cryogenic Fluids Code, NFPA 52, Vehicular Natural Gas Fuel Systems Code or NFPA 58, Liquified Petroleum Gas Code. These codes contain requirements on the specific containers, building construction, and/or sprinkler design required for the storage of these more hazardous materials. These are just some of the many unique fire protection challenges for warehouse and other similar distribution centers. For more information check out our Warehouse Fact Sheet. Also, come check out NFPA’s 125th Anniversary Conference series on November 16, which will feature presentations on automatic warehouse storage and retrieval systems, the importance of water supply assessment, a review of the changes to the 2022 edition of NFPA 13, and other relevant systems, storage, and suppression topics.

Transformer Fire Protection

While superheroes and the big box office may have everything thinking about robots when we talk about transformers, they are actually a much more important device that is essential for the transmission, distribution, and utilization of alternating current electric power. What are transformers and what do they do? In basic terms a transformer is a device that transfers electric energy from one AC circuit to another, either increasing or reducing the voltage. This is done for several reasons, but two main purposes are to reduce the voltage of conventional power circuits to operate low-voltage devices and to raise the voltage from electric generators so that electric power can be transmitted over long distances. They have been in use for a long time and are an essential piece of our electrical infrastructure. The most common transformer that people often see are located on telephone poles. Why are transformers hazardous? Transformers are often times filled with oil for insulation, to prevent electrical arcing and to serve as a coolant. This oil is similar to mineral oil and very flammable. When a transformer fails it can lead to an intense fire and violent explosion (feel free to check out one of the many videos online on exploding transformers). Transformers can hold anywhere between a few gallons to thousands of gallons. Transformers can be installed indoors or outdoors, but indoor transformers typically are not filled with oil while outdoor transformers often are. Oil insulated transformer protection methods Some of the main considerations when talking about transformer fire protection are fire walls & separation, water based fire protection systems, containment, drainage and lightning protection. Fire Wall & Separation Ideally, we want to prevent transformers from catching fire, but in the event one does catch fire or explode we want to limit the damage and potential spread of fire. This can be done by several means, the most common being physical separation and fire walls. NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations,  recommends that transformers with more than 500 gallons (1900 L) of oil be protected by a fire wall rated for 2 hours that is extended 1ft (300 mm) vertically and 2ft (600 mm) horizontally beyond the transformer. In lieu of a fire wall, physical separation is recommended anywhere from 5 to 25 ft (1.5 to 15 m) based on the oil capacity of the transformer. Fire Protection Systems NFPA 15, Standard for Water Spray Fixed Systems for Fire Protection, contains requirement on how transformers should be protected using a water spray system. If requires  0.25 gpm/ft2 [10.2 (L/min)/m2] of water to be discharged onto the envelope of the transformer itself and 0.15 gpm/ft2 [6.1 (L/min)/m2]  on the surrounding area for exposure protection. The water supply for such a system needs to be able to keep up with the designed flow rate of the system as well as 250 gpm (946 L/min) for a hose for the duration of 1 hour. Another important protection feature is a containment pit and drainage system to help retain any spilt transformer oil or discharge from a fixed water spray system. If a containment area is designated, then the fire wall should at least extend to the edge of that area. Since lightning is a potential ignition source for a transformer fire lightning protection should also be provided. For more information on how lightning protection works see NFPA 780, Standard for the Installation of Lightning Protection Systems. Transformer failures can be extremely dangerous but with the right precautions in place fires can be controlled to limit damage to the surrounding components, minimize plant downtime and improve survivability of plant staff. There is a lot more that goes into panning and designing a safe transformer installation, but this addresses the main concepts and ideas. For more information on fire protection recommendation for power generating plants check out NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations.
Solar panels

Residential Energy Storage System Regulations

NFPA 855, Standard for the Installation of Stationary Energy Storage Systems, contains requirements for the installation of energy storage systems (ESS). An ESS system 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. NFPA 855 covers a lot of different ESS topics but this blog will focus on some of the considerations related to installing an ESS in a residential one or two family home. The exact requirements for this topic are located in Chapter 15 of NFPA 855. What is an Energy Storage System? An energy storage system is something that can store energy so that it can be used later as electrical energy. The most popular type of ESS is a battery system and the most common battery system is lithium-ion battery. These systems can pack a lot of energy in a small envelope, that is why some of the same technology is also used in electric vehicles, power tools, and our cell phones. ESS are often installed in homes to supplement solar panels, but they can also be used to offset the price of electricity by charging when electricity is cheap and discharging when it is more expensive. Size limitations The residential chapter of NFPA 855 addresses the installation of residential ESS units between 1kwh and 20 kwh. After individual units exceed 20kWh it will be treated the same as a commercial installation and must comply with the requirements of the rest of the standard. There are also limitations on how much total energy can be stored in certain areas of a household. If you go beyond those thresholds, then you need to comply with the requirements for commercial installations. Area Maximum Stored Energy Utility closets, storage or utility spaces 40 kWh Garages and detached structures 80 kWh Exterior walls 80kWh Outdoor installations 80kWh   Location Energy storage systems can pose a potential fire risk and therefore shouldn’t be installed in certain areas of the home. NFPA 855 only permits residential ESS to be installed in the following areas: Attached garages Detached Garages On exterior walls at least 3 ft (914 mm) away from doors or windows Outdoors at least 3 ft (914 mm) away from doors or windows Utility closets Storage or utility spaces ESS can be installed in any of those locations, however if the room is unfinished, the walls and ceiling need to be protected by at least 5/8 in. (16 mm) gypsum board. Certain types of energy storage systems have the potential to discharge toxic gas during charging, discharging, and normal use. It makes sense that these types of energy storage systems are only permitted to be installed outdoors. One last location requirement has to do with vehicle impact. One way that an energy storage system can overheat and lead to a fire or explosion is if the unit itself is physically damaged by being crushed or impacted. Because of this risk, any battery systems installed in a location where they are subject to vehicle damage needs to be protected by approved barriers, usually in the form of safety bollards. No one wants bollards installed in their garage or driveway so ideally one would be able to move their system out of reach from vehicles. This can be accomplished by either relocating the ESS to a place where vehicles can’t access or mounting it higher on the wall so vehicles can’t accidentally run into it. Fire Detection If there is an ESS in your home then interconnected smoke alarms are required to be installed throughout your house, including any garages or rooms housing ESS units. If you run into a situation where you can’t install a smoke alarm, such as an attached garage, a heat detector must be installed and be connected to the smoke alarms in the rest of the house. Electric Vehicle Use As global sales of electric vehicles seem to be exponentially growing the committee that wrote NFPA 855 thought it would be important to include requirements for houses that will use their electric vehicles as energy storage systems. There are really only two main requirements. First, any electric vehicle used to power a dwelling while parked needs to comply with the manufacturer’s instructions and NFPA 70, National Electrical Code®. Second, the use of a vehicle to power a home can’t exceed 30 days. While there are a lot of requirements for commercial energy storage systems the rules and regulations are much more relaxed for smaller systems being installed in residential one- and two-family dwellings. I hope you enjoyed this blog. ESS is certainly a hot topic. If you are interested in  ESS, please plan to attend either the Keeping Hazardous Environments Safe one-day conference on October 5th where ESS will be discussed during two industry panel discussions or the Global Trends and Research conference on November 2, where experts will discuss ESS explosion risks during a two-hour roundtable. All NFPA 125th Anniversary Conference Series sessions are available for one year after the live date, via on-demand. For related training, articles, research reports, and more check out
Train at a station

Means of Egress with NFPA 130

NFPA 130 is the Standard for Fixed Guideway Transit and Passenger Rail Systems. It contains requirements for train stations, subway stations, the trains or subway cars themselves, and the tracks or paths these vehicles travel on. While NFPA 130 covers a wide array of topics this blog is going to concentrate on the unique means of egress requirements for fixed guideway transit and passenger rail stations. Means of Egress First, what is the means of egress? In layman’s terms the means of egress is the pathway out of a building or structure that leads to a point of safety and is comprised of three parts, the exit access, exit and exit discharge.    EXIT ACCESS - The exit access is the path that leads to the exit EXIT - The exit is the portion of a means of egress that is separated from all other spaces of the building or structure by construction, location or equipment as required to provide a protected way of travel to the exit discharge. Examples include an exit door that leads directly outside, an exit staircase, exit passageways, etc. EXIT DISCHARGE - Exit discharge is that portion of a means of egress between the termination of an exit and a point of safety. In NFPA 130 the point of safety can either be the concourse or a point of safety outside of the building. In general, the station needs to comply with the means of egress requirements in NFPA 101®, Life Safety Code®, for New Assembly Occupancies except where it is modified by NFPA 130. For more information on the means of egress check out this blog! The following sections discuss those modifications. Occupant Load Determining the occupant load is needed to figure out how quickly those occupants can egress the station. To determine the occupant load we need to assume that all of the trains are simultaneously entering the station full of passengers who need to disembark and that there is a full train’s worth of people waiting on the platform to enter the train. So, the occupant load includes both the people exiting the train as well as those waiting on the platform. This will give us a worst-case scenario of having all of the trains recalled to the station at once and having to evacuate both the vehicle and station. There is also the occupant load for each platform that must be calculated in order to make sure each platform can be evacuated in a timely manner. This number is based on peak ridership numbers, which can often require an analysis be done to determine peak ridership statistics. Similar to the station occupant load, the platform occupant load needs to assume a full train has pulled into the station and drops off an entire train load while there is another train load of people waiting on the platform. Evacuation Time When looking at evacuation times there are two main figures that must be considered. The first is the platform evacuation time which is required to be less than 4 minutes. The second is the station evacuation time, in which the occupant load needs to be able to reach a point of safety in under 6 minutes.  Travel Distance There are also limitations on travel distances and common paths of travel for platforms. Travel distance is your natural path of travel measured from the most remote point on the platform to the where the means of egress path leaves the platform. NFPA 130 requires that the travel distance is 100m (325ft) or less. There is also the concept of a common path of travel which is measured in the same manner as travel distance but terminates at that point where two separate and distinct routes become available. The common path of travel is not allowed to exceed 25m (82ft) or one car length, whichever is greater. Platforms Corridors & Ramps Many of the requirements for platforms, corridors and ramps are summarized in the table below. In addition to those limitations, when calculating available egress capacity on platforms, corridors, and ramps, 12 inches must be subtracted from each wall and 18 inches subtracted from the platform edge.   Capacity Travel Speed Minimum width Platforms 2.08 p/in.- min (0.0819 p/mm-min) 124 ft/min (37.7 m/min)   44 in. (1120 mm) Corridors 2.08 p/in.- min (0.0819 p/mm-min) 124 ft/min (37.7 m/min)   44 in. (1120 mm) Ramps 2.08 p/in.- min (0.0819 p/mm-min) 124 ft/min (37.7 m/min)   44 in. (1120 mm) Concourse   200 ft/min (61.0 m/min)   Stairs   48 ft/min (14.6 m/min)* 44 in. (1120 mm) Escalators 1.41 p/in.-min (0.0555 p/mm-min) 48 ft/min (14.6 m/min)*   Elevators carrying capacity for 30 minutes     *Travel Speed for vertical component of travel Escalators NFPA 101 typically doesn’t allow escalators to be used as a component in the required means of egress but because of the short evacuation timeframe, NFPA 130 allows it. When determining egress capacity for escalators there are a few rules that need to be followed. One escalator at each level must be assumed to be out of service and escalators cannot account for more than 50% of the egress capacity for a level unless they meet additional criteria. Elevators Elevators are another unique component of the means of egress that is allowed to be used in fixed guideway and passenger rail stations, but they also come with additional rules. One elevator must be considered out of service, elevators can’t account for more than 50% of the egress capacity and one elevator must be reserved for the fire service. The capacity of elevators is determined by calculating the carrying capacity over a 30-minute timeframe. Elevators also must meet certain construction requirements and they need to be accessed through holding areas or lobbies. Exit Hatches Exit hatches are another unique component of the means of egress permitted for fixed guideway and passenger rail stations. Exit hatches must be manually opened from the egress side with only one releasing operation requiring less than 30lb (130N) of force and have a hold-open device. It also needs to be clearly marked on the discharge side to prevent blockage. Fare Barriers Fare barriers are typically gate type or turnstile type, each of which have additional requirements that must be met to be allowed in the means of egress. Fare barriers are a unique characteristic of a station and have unique requirements. For a fare barrier to be allowed in the means of egress it must either be designed to release in the direction of travel during an emergency or be able to open by providing 15lbf (66N) of force in the egress direction. Platform Edge Provisions Finally, the platform edge is another unique feature of a station. Guards are not required along the trainway side of the platform edge. Certain horizontal sliding platform screens or doors are permitted to separate the platform from the trainway, but the doors or screens must open with less than 50 lb (220N) of force at any stopping position of the train and it needs to be able to withstand the positive and negative pressures caused by the passing trains. There are many unique fire and life safety elements found in Fixed Guideway Transit and Passenger Rail Systems. This blog discussed some of the unique means of egress characteristics, but NFPA 101 contains many more requirements that must be followed. 

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