Fire, smoke, and combination fire/smoke dampers are crucial pieces of equipment used to reduce the spread of fire and smoke throughout a building. For an overview of the basics on fire and smoke dampers refer to this newly developed fact sheet. As with all fire protection and life safety equipment, fire and smoke dampers must be properly inspected, tested, and maintained to ensure that they will operate when needed. This blog will break down the requirements for the inspection, testing, and maintenance (ITM) requirements of fire dampers, smoke dampers, and combination fire/smoke dampers. Although the ITM requirements for each seem similar, there are some variations in the inspection and testing requirements. Fire Dampers Chapter 19 of NFPA 80, Standard for Fire Doors and Other Opening Protectives, provides the ITM requirements for fire dampers. Operational Test An operational test is performed (typically by the installation personnel) right after the damper is installed to confirm the following: ·      Damper fully closes. ·      There are no obstructions to the operation of the damper. ·      There is full and unobstructed access to the damper. ·      For dynamic dampers, the velocity in the duct is within the velocity rating of the damper. ·      All indicating devices are working and report correctly. ·      The fusible link (if equipped) is the correct temperature classification and rating. Acceptance Testing An acceptance test is a test of the damper that is completed by a qualified person after the damper is installed, an operational test is completed, and the entire heating, ventilation, and air conditioning (HVAC) system is complete. The acceptance test is performed to confirm the following prior to placing the entire system in service: ·      The damper is not damaged or missing any parts. ·      If actuated, dampers close fully upon disconnection of electrical power or air pressure. ·      If actuated, dampers fully reopen when electrical power or air pressure is reapplied. ·      If non-actuated, the damper closes upon removal of the fusible link and is manually reset to the full-open position. Testing must be done under maximum airflow after HVAC system balancing, unless acceptance testing is being peformed for dampers with fusible links. In that case, it is permitted to turn the fan in the system off. Periodic Testing Fire dampers need to be inspected and tested 1 year after the initial acceptance test and then every 4 years, unless the dampers are installed in a hospital, in which case they can be inspected and tested every 6 years. During the periodic inspection of an actuated fire damper, the following needs to be completed: ·      Confirm that the damper is in the full-open or full-closed position as required by the system design. ·      Visually confirm the damper moved to the full-closed or full-open position when commanded. ·      Visually confirm that the damper returns to the original operating position as required by the system design. During the periodic inspection of a non-actuated fire damper, the following needs to be completed: ·      Confirm the fusible link is not painted. ·      Confirm the damper fully closes when the fusible link is removed or activated with the damper in the full-open position. ·      Where equipped, confirm that the damper latches in the full-closed position. ·      Confirm that the damper is returned to the full-open and operational position with fusible link installed. Smoke Dampers   Chapter 7 of NFPA 105, Standard for Smoke Door Assemblies and Other Opening Protectives, provides the inspection, testing, and maintenance requirements for smoke dampers, which are outlined below. Smoke dampers that are part of a smoke control system need to be inspected and tested in accordance with NFPA 92, Standard for Smoke Control Systems. Operational Test An operational test is performed after the damper is installed and after the building’s heating ventilation and air conditioning (HVAC) system has been fully balanced to confirm the following: ·      Damper fully closes under both the normal HVAC airflow and non-airflow conditions. ·      There are no obstructions to the operation of the damper. ·      There is full and unobstructed access to the damper. ·      All indicating devices are working and report correctly. Acceptance Testing An acceptance test is a test of the damper that is completed by a qualified person after the damper is installed, an operational test is completed, and the entire HVAC system is complete to confirm the following prior to placing the entire system in service: ·      The damper is not damaged or missing any parts. ·      Dampers close fully upon disconnection of electrical power or air pressure. ·      Dampers fully reopen when electrical power or air pressure is reapplied. Testing must be done under maximum airflow after HVAC system balancing. Periodic Testing Smoke dampers need to be inspected and tested 1 year after the initial acceptance test and then every 4 years, unless the dampers are installed in a hospital, in which case they can be inspected and tested every 6 years. During the periodic inspection, the following needs to be completed: ·      Confirm that the damper is in the full-open or full-closed position as required by the system design. ·      Visually confirm the damper moved to the full-closed or full-open position when commanded. ·      Visually confirm that the damper returns to the original operating position as required by the system design. Combination Fire/Smoke Dampers Combination Fire/Smoke Dampers need to meet the requirements for both fire dampers and smoke dampers when it comes to ITM. Documentation All inspections and tests of fire, smoke, and combination fire/smoke dampers need to be documented and maintained for at least three test cycles. These documents need to include the following: ·      Location of the damper ·      Date(s) of inspection ·      Name of the inspector ·      Deficiencies discovered, if any ·      Indication of when and how deficiencies were corrected, if applicable Maintenance Proper maintenance of fire, smoke, and fire/smoke dampers is crucial to ensure that they remain operational. If a damper is found to not be operational, repairs need to be completed without delay and a periodic test must be completed after the repair is completed to ensure the damper’s operation. All exposed moving parts of the damper need to be lubricated as required by the manufacturer and any reports of an abrupt change in airflow or noise from a duct system needs to be investigated to ensure that it is not related to the damper operation. Summary Proper inspection, testing, and maintenance of fire, smoke, and fire/smoke dampers ensure they are installed and operating properly in the event of an emergency. For more information about the basics of fire, smoke, and combination fire/smoke dampers, check out this fact sheet.

Each year, the Fire Protection Research Foundation hosts the SUPDET® (short for Suppression and Detection) Conference to bring together industry experts to collaborate in panel discussions and participate in engaging education sessions on the latest research techniques and applications used for fire suppression, detection, signaling, and other emerging technologies. At the conclusion of the conference, attendees vote on the “Best Paper” (presentation) for each category of suppression and detection. The Fire Protection Research Foundation is proud to announce the 2022 SUPDET winners of the William M. Carey Award (suppression) and the Ronald K. Mengel Award (detection). The William M. Carey Award for the best presentation in the suppression category goes to Jeremy Souza of Code Red Consultants for his presentation “Going Fluorine Free – Converting a Legacy AFFF System to Fluorine-Free Foam.” The Ronald K. Mengel Award for the best presentation in the detection category is being awarded to two individuals, as there was a tie in votes: Arjen Kraaijeveld of HVL for his presentation “Reliable Fire Detection Systems for Residents with Drug and Psychiatric Disorders” and Travis Montembeault of Peerless Pump Company for his presentation “Smart fire protection systems improve overall reliability and decision making.” These winners will be presented with the awards at the 2023 SUPDET Conference, which will be September 12–14 in Northbrook, Illinois. Save the date! The awards’ namesakes It is with grateful appreciation of William Carey and Ronald Mengel that the Fire Protection Research Foundation presents these two awards each year. William Carey was a leading authority on fire safety. He spent 34 years as a professional engineer at Underwriters Laboratories, Inc. Throughout his career, Carey was a project engineer, giving presentations on fire safety products and investigating products to determine if they met UL standards. He also volunteered at several industry-related associations, including the Society of Fire Protection Engineers (SFPE), and served on many NFPA technical committees. Later in his career, Carey was a senior staff engineer involved in working at UL’s large-scale fire testing facility, where he specialized in testing fire safety products, including sprinkler systems and portable fire extinguishers. He died unexpectedly at the early age of 56. He had an extraordinary knowledge and experience in his area of expertise and contributed to a better understanding of fire for engineers. Ronald Mengel had a long-distinguished career in the fire detection and alarm industry. He served in the US Navy and worked for General Electric and later Honeywell’s System Sensor Division. Mengel was a valued member of the fire protection community and volunteered for several industry-related associations including the Society of Fire Protection Engineers (SFPE), Automatic Fire Alarm Association (AFAA), National Electrical Manufacturing Association (NEMA) and the Foundation’s Fire Detection and Alarm Research Council. Congratulations Jeremy, Arjen, and Travis on your well-deserved awards. We look forward to seeing you in the fall! Please save the date, and check out our call for papers for 2023!

When thinking about automatic sprinkler protection for a warehouse, one might start by asking themselves, what will be stored in the building? That will define the fire hazard. This is a great starting point, but it’s also important to ask yourself additional questions: What type of operations will take place in the building? Will the owner have the need to store any idle pallets?   Although the latter may seem like an odd question, pallets can be a significant fire hazard—at times even greater than the commodities stored in the building. Not considering the hazard of idle pallets may result in an automatic sprinkler system that will not be effective at controlling a potential fire within the building.   Pallet fires have been shown to release large amounts of energy and challenge the effectiveness of automatic fire sprinkler systems. Stacked pallets provide airflow spaces that can optimize fire spread, while the upper pallets shield the lower ones, allowing what could be a concealed fire to rapidly develop. This type of fire is a challenge for even a well-designed sprinkler system. The 2022 edition of NFPA 13, Standard for the Installation of Sprinkler Systems, has criteria specifically for idle pallet storage in section 20.17, which is based on the type and storage arrangement utilized. It is important to note that idle pallets are treated separately from the other types of stored commodities and low-piled storage in NFPA 13.   Idle pallet storage is not limited to warehouses either. It can be a concern anywhere goods are received in bulk and broken down for sales or distribution. This may include buildings such as big-box stores, grocery stores, distribution centers, factories, and even smaller stores like pharmacies and convenience stores. Let’s review the types of pallets and configurations covered in NFPA 13 and some of the schemes provided for automatic fire sprinkler system design. Types of Pallets   Pallets can be either constructed from wood. NFPA 13 defines a wood pallet as “a pallet constructed entirely of wood with metal fasteners,” while the standard defines a plastic pallet as “a pallet having any portion of its construction consisting of a plastic material.”    The images below are examples of wood and plastic pallets. For the purpose of automatic fire sprinkler design, plastic pallets can be treated equivalent to wood pallets when it’s been demonstrated their fire hazard is equal to or less than that of wood pallets and they’ve been listed for such equivalency.     Storage Arrangements   Although NFPA 13 recognizes idle pallet storage can occur outside, in a detached building, or indoors, the standard only provides protection criteria for indoor pallet storage. In this case, pallets can be arranged in stacks on the floor and on racks without solid shelves. The height of the pallet “pile,” separation distance from other “piles,” and the height of the ceiling are all a part of the storage arrangement and will play a role in identifying the correct protection scheme. It should be noted that the storage of idle pallets on solid-shelf racks is not permitted due to the difficulty in extinguishing idle pallet storage combined with the shielding of the shelves.   Protection Schemes   Density Area Method – Ordinary Hazard Group II   When designing the sprinkler system for protection of idle wood pallets, it’s important to remember both wood and plastic pallets can be stored inside and protected by a density/area design criteria equivalent to Ordinary Hazard Group II. For wood pallets, the pile cannot be more than 6 ft (1.8 m) in height, and for plastic pallets, the pile cannot be more than 4 ft (1.2 m) in height. In both cases, the piles must be separated by a minimum of 8 ft (2.4 m) of clear space or 25 ft (7.6 m) of stored commodity. Each wood pile is limited to four stacks and each plastic pile is limited to two stacks. This scheme allows occupancies such as department stores and small factories the ability to store idle pallets in limited quantities.   Control Mode Density/Area Method   The protection schemes for wood pallets using the density/area method allow storage heights between 6 ft and 20 ft (1.8 m–6.1 m), with maximum ceiling heights up to 30 ft (9.1 m), utilizing 0.2 gpm/ft2–0.6 gpm/ft2 (8.2 mm/min–24.5 mm/min) over areas between 2000 ft2–4500 ft2 (185 m2–450 m2). When plastic pallets are not separated in a dedicated storage room, the piles can be up to 10 ft (3.0 m) in a building, with a maximum ceiling height of 30 ft (9.1 m) and a density of 0.6 gpm/ft2 over 2000 ft2 (24.5 mm/min over 185 m2), utilizing a minimum K-factor of 16.8 (240).   Control Mode Density/Area Method – Dedicated Room   Plastic pallets are permitted to be stored in a dedicated room separated from other storage by a 3-hour-rated fire wall with storage piles up to 12 ft (3.7 m) utilizing a density of 0.6 gpm/ft2 (24.5 mm/min) over the entire room and protection from the steel columns in the room. Wood pallets do not have the same protection scheme equivalent.   Control Mode Specific Application (CMSA) Sprinklers   Only wood pallets may be protected using the control mode specific application (CMSA) method. Pallet storage can be up to 20 ft (6.1 m) in height, with maximum ceiling heights between 30 ft and 40 ft (9.1 m-12.2 m). The range of available K-factor designs is 11.2–19.6 (160–280) with different criteria for minimum design pressure and number of heads in the design. Currently, storage on racks without solid shelves is not permitted with the CMSA design scheme.   Early Suppression Fast Response (ESFR) Sprinklers   Early suppression fast response (ESFR) sprinklers are designed for challenging fires, which makes them an option for idle pallet storage. NFPA 13 has protection schemes for wood pallet arrangements, both on the floor and on racks without solid shelves, at storage heights from 20 ft­–35 ft (6.1 m-10.7 m), with maximum ceiling heights between 30 ft–40 ft (9.1 m-12.2 m), utilizing K-factor designs from 14–25.2 (200–360) and minimum operating pressures between 15 psi–75 psi (1 bar–5.2 bar). The schemes for plastic pallets are not limited in storage height, but are limited in maximum ceiling height, with schemes up to 40 ft (12.2 m) in height, utilizing K-factor designs from 14–25.2 (200–360) and minimum operating pressures between 35 psi and 75 psi (1 bar–5.2 bar).   High Expansion Foam   For plastic pallets stored in a dedicated room separated from other storage by a 3-hour-rated fire wall with storage piles up to 12 ft (3.7 m), a high expansion foam system combined with a sprinkler density of 0.3 gpm/ft2 (12.2 mm/min) over the entire room and protection from the steel columns in the room can also be utilized.   Specific Test Data   Recognizing the significant fire challenge of idle plastic pallet storage, any protection scheme that is based on test data is not only permitted but encouraged to take precedent over the listed protection schemes. However, this same clause does not exist for the protection of idle wood pallets.   Summary   The storage of idle pallets is a significant fire hazard. When this hazard is not considered during the automatic fire sprinkler system design, the potential exists for a significantly undersized sprinkler system. Whether you’re designing a warehouse or simply a storage/loading dock in an office building, it is important to consider the storage of idle wood pallets in the design. The type of pallets, height of the pallet piles, and ceiling height all influence the available protection schemes. If you’re looking for more information on sprinkler system design in storage occupancies, check out the NFPA 13 Storage Protection Requirements and Assessment (2022) Online Training Series.

Mobile energy storage systems are being deployed in jurisdictions around the world, and—as demonstrated by a 2023 New Year’s Day mobile energy storage system fire—accidents can happen. We want to make sure communities are prepared for when these systems are deployed in their backyard. This blog will outline key considerations for mobile energy storage systems. To see the full requirements, check out the latest edition of NFPA 855, Standard for the Installation of Stationary Energy Storage Systems. What is a mobile energy storage system?   An energy storage system (ESS) is a group of devices assembled together that is capable of storing energy in order to supply electrical energy at a later time. A mobile energy storage system is one of these systems that is capable of being moved and typically utilized as a temporary source of electrical power. In practice, this is often a battery storage array about the size of a semi-trailer. Mobile energy storage systems can be deployed to provide backup power for emergencies or to supplement electric vehicle charging stations during high demand, or used for any other application where electrical power is needed. While there are various types of ESS and many battery technologies, this blog will focus on the most prevalent type—lithium-ion battery energy storage systems. Many of these requirements apply to any type of mobile energy storage system; see NFPA 855 requirements for details on other technologies. When does NFPA 855 apply to mobile energy storage systems? The scope of NFPA 855 states that it applies to “mobile and portable energy storage systems installed in a stationary situation.” It also goes on to mention that the storage of lithium-ion batteries is included in the scope of the document. The application section then limits the application of the standard to certain-sized mobile energy storage systems. For all types of lithium-ion batteries, the threshold is 20 kWh (72 MJ) before the requirements of NFPA 855 apply. For batteries in one- and two-family dwellings and townhouse units, that threshold is reduced to 1 kWh (3.6 MJ). For more information on residential ESS requirements, check out our previous blog on that topic. When looking at how a mobile energy storage system works, we break its use down into three phases: the charging and storage phase, the in-transit phase, and the deployed stage. This is how I’ll break down the requirements as well. Charging and storage When charging and storing a mobile energy storage system, the requirements are relatively straightforward. The system should be treated as a stationary system as far as the requirements of NFPA 855 go. These requirements will vary based on whether the system is being stored indoors, outdoors, on a rooftop, or in a parking garage. In-transit While a mobile energy storage system is in transit from its normal charging and storage location to its deployment location, it typically travels on roads that are governed by the governmental transportation authority (in the US, that would the Department of Transportation). However, when the mobile energy storage system needs to be parked for more than an hour, it needs to be parked more than 100 ft (30.5 m) away from any occupied building, unless the authority having jurisdiction (AHJ) approves an alternative in advance.  Deployment documents Before a mobile energy storage system is deployed, it needs to be approved by the AHJ, and a permit must be obtained for the specific use case. The permit application must include the following items: Mobile Energy Storage System Permit Application Checklist o Information for the mobile energy storage system equipment and protection measures in the construction documents o Location and layout diagram of the area in which the mobile energy storage system is to be deployed, including a scale diagram of all nearby exposures o Location and content of signage o Description of fencing to be provided around the energy storage system and locking methods o Details on fire protection systems o The intended duration of operation, including connection and disconnection times and dates o Description of the temporary wiring, including connection methods, conductor type and size, and circuit overcurrent protection to be provided o Description how fire suppression system supply connections (water or another extinguishing agent) o Maintenance, service, and emergency response contact information. Deployed There are restrictions on where mobile energy storage systems can be deployed. For example, they are not allowed to be deployed indoors, in covered parking garages, on rooftops, below grade, or under building overhangs. There is also a restriction on how long mobile energy storage systems can be deployed before they need to be treated as a permanent energy storage system installation, and that threshold is 30 days. Additional limitations for where a mobile energy storage system can be deployed include a 10 ft (3 m) limitation on how close it can be to various exposures and a 50 ft (15.3 m) limitation on how close it can be to specific structures with an occupant load of 30 or greater. See NFPA 855 or the image above for more details on the exposures and occupancies. An energy storage system contains a large amount of energy stored in a small space, which may make it the target for those who look to cause harm. For this reason, a deployed mobile energy storage system is required to be provided with a fence with a locked gate that keeps the public at least 5 ft (1.5 m) away from the ESS. Conclusion There are many applications where mobile energy storage systems can play a pivotal role in helping deliver electricity to where it is needed. While this technology has great practical applications and even more potential, it’s important to recognize that it also brings unique hazards. Adherence to the requirements of NFPA 855 can help keep our communities safe while embracing current technology. Here are some additional NFPA® resources related to ESS safety: -       Energy storage system landing page -       Energy Storage and Solar Systems Safety Online Training -       Energy Storage Systems Safety Fact Sheet

Are you in the field installing a fire alarm system and need to know what the required fire alarm pull station height is? Or maybe you are working on a fire alarm design detail and want to know what the required height is for your fire alarm call point. You’re not the first one to ask this question, so I will get right into it. What is the required height for a fire alarm pull station? The simple answer that the operable part of the pull station needs to be at least 42 in. (1.07 m), and not more than 48 in. (1.22 m), above the finished floor. Additionally, one pull station needs to be within 5 ft (1.5 m) of each exit doorway on each floor where required to be installed in a building. Both of these requirements are shown below. The code requirements NFPA 72®, National Fire Alarm and Signaling Code®, refers to a fire alarm pull station as a manually actuated alarm-initiating device, and defines it as a manually operated device used to initiate a fire alarm signal. Other publications may refer to a fire alarm pull station as a manual fire alarm station, pull station, fire box, call point, and so on. The requirements for the installation height can be found in Section 17.15 of the 2022 edition of NFPA 72. If you want to learn how you can easily find those requirements in the code using NFPA LiNK®, take a look at the video below.     It’s important to note that NFPA 72 does not require that manual initiating devices be installed in buildings. Instead, it provides the installation requirements when the devices are required by other codes such as NFPA 101®, Life Safety Code®, NFPA 1, Fire Code, or NFPA 5000®, Building Construction and Safety Code®. Mounting the back box When mounting the back box for a manual pull station it is important to know the make and model of device that will ultimately be installed. As you saw above, the measurements are taken to the operable part of the device, not the middle of the device. Additionally, these measurements are taken from the finished floor, so when installing back boxes prior to the installation of the flooring, the thickness of the flooring must be accounted for in the measurement. Tolerances NFPA 72 allows a tolerance for the installation of devices. This tolerance is noted in 1.6.5 and A.1.6.5. Where dimensions are expressed in inches, it is intended that the precision of the measurement be 1 in., which would be plus or minus 1⁄2 in. The conversion and presentation of dimensions in millimeters would then have a precision of 25 mm, which would be plus or minus 13 mm. Therefore, the maximum height of the operable portion of the manually actuated alarm-initiating device could be up to 48.5 in. (1.233 m) if you account for the allowable tolerances in NFPA 72. Other wall-mounted appliance and device heights Do you want to learn more about installation heights for other fire alarm devices, appliances, and equipment? The video referenced earlier in this blog outlines how you can use the direct navigation feature of NFPA LiNK (NFPA DiRECT®) to find the mounting heights not only for fire alarm pull stations, but also for other wall-mounted fire alarm equipment, as well as all of the supporting code requirements.  

Automatic fire sprinkler systems have consistently demonstrated their ability to reduce the impact of unwanted fires.   But when a sprinkler system fails, many times it is due to insufficient water reaching the fire. An NFPA® research report titled “U.S. Experience with Sprinklers” found that when a system fails to contain a fire, 50 percent of the time it was because water did not reach the fire at all, and 31 percent of the time not enough water reached the fire.   These statistics underscore the importance of effectively calculating the water demand needed for the automatic fire sprinkler system; otherwise, the system may not be effective at reducing the impact of a fire.   This is the first in a series of blogs aimed at providing an overview of the basics of fire sprinkler design calculations (demand calculations) using the density/area design method found in the 2022 edition of NFPA 13, Standard for the Installation of Sprinkler Systems. Today we will focus on subsection 19.2.3, which addresses the water demand, and paragraph 28.2.4.2, which specifies the hydraulic calculation procedures specific to the density/area design method.   Density/area method   The density/area method can be generally defined as a given amount of water (sprinkler discharge rate) over a specified area. This given amount of water is known as the design density, which is intended to provide cooling and wet adjacent surfaces with the goal of controlling an unintended fire until it can be fully extinguished by emergency services. The area is the expected area of sprinkler operation, or remote area for which the given amount of water (design density) must be applied. For water demand calculations, it’s assumed all sprinklers in this area will operate. This area is often adjusted for things like quick-response sprinklers, sloped ceilings, dry-pipe, double interlock systems, and high-temperature sprinklers.   Remote area   When calculating the water demand needed for the system it is imperative that the correct location on the sprinkler system be chosen as the remote area. Although most fire sprinkler system calculations are done utilizing hydraulic calculation software, many are integrated into computer aided drafting (CAD) programs. The ability of the program to correctly calculate the water demand is directly related to the user’s ability to select the correct area.   The area selected should be the hydraulically most demanding, which is often physically the furthest point from the sprinkler riser on the system. However, in some instances, pipe sizes may make an area physically closer to the riser more hydraulically demanding. An example of this may be an instance closer to the sprinkler riser, which utilizes a more condensed spacing than the physically most remote portion of the system. When in doubt, it is best to calculate multiple areas.   Identifying the remote area   The steps in identifying the remote area involve determining the area (square footage or square meters) from the design criteria, applying the necessary adjustments to this area, calculating the shape, determining the number of sprinklers necessary in the area, and selecting those sprinklers that meet the remoteness and shape criteria. Let’s walk through a basic example for remote area selection on a system with a main line and branch lines (not gridded or looped).   The initial step is to determine the area (square footage or square meters) from Chapter 19. Since we’re utilizing the density/area method on a new system, Table 19.2.3.1.1 applies. Determining the occupancy hazard classification is very specific to the area being protected and is a bit out of scope for this blog but certainly a topic we will cover in this series. For the sake of our calculation, let’s assume we determined the occupancy to be an Ordinary Group I hazard.     You’ll notice we’re given two options for each hazard. This is because areas adjacent to combustible concealed spaces present a unique challenge—the fire may establish itself in the concealed space and a greater number of heads may activate. Let’s assume we’ve determined we are not adjacent to a combustible concealed space, so the 0.15 gpm/ft2 (6.1 mm/min/m2) over 1500 ft2 (140 m2) applies, thus our area is 1500 ft2 (140 m2). Remember, this area may be adjusted for things like quick-response sprinklers, sloped ceilings, dry-pipe, double-interlock systems, and high-temperature sprinklers. For our example, let’s assume none of these adjustments applies.   After determining the size of the remote area, we’ll need to determine its shape. Paragraph 28.2.4.2.1 indicates that “a rectangular area having a dimension parallel to the branch lines at least 1.2 times the square root of the area of sprinkler operation (A)” is utilized. As an equation that is:   L = 1.2√A Where:  L = the dimension parallel to the branch line (ft or m) A = the area of operation (ft2 or m2)   For the sprinkler operation area in this example, we get:   L = 1.2√(1500 ft2  (L = 1.2√140 m2) L = 46.5 ft (L = 14.2 m)   We’re going to assume we’re utilizing a sprinkler coverage area of 120 ft2 (11.1 m2), which is under the maximum allowable square footage for an Ordinary Group I hazard with standard-spray sprinklers of 130 ft2 (12 m2) with sprinklers spaced 12 ft (3.6 m) apart along the branch line and branch lines 10 ft (3 m) apart as shown below.     The next step is to determine the number of sprinklers in the area. To accomplish this, we’ll divide the area from Table 19.2.3.1.1 by the coverage area per sprinkler.   1500 ft2 / 120 ft2 = 12.5 sprinklers   Since it’s not possible to activate half a sprinkler head, we round the number to 13 sprinklers.   Now that we have the shape and the number of sprinklers in the design area, we apply that to our layout and select the 13 most remote sprinklers that meet our remote area shape criteria.   To meet the shape requirement of 46.5 ft (14.2 m) long, we’d need to utilize five sprinklers along the branch line. To meet the number of sprinklers, we’d need an additional eight sprinklers, five along the next branch line and three along the third. We’re permitted to utilize any of the sprinklers along the third branch line. Most commonly, the ones closest to the cross main are selected as they will result in the greatest flow. This is shown graphically below.     As you can see, even in this simple example there are nuances to selecting the design. Keep in mind, this was one of many design options for new sprinkler systems in NFPA 13. Evaluation of existing systems has separate criteria. Make sure to utilize the correct option for your situation.   Wrapping up   Even when utilizing computer software, engineers and designers need to select these sprinklers correctly to ensure they accurately provide the water demand needed in the event of an unwanted fire. Next up in this series of blogs we’ll look at the K-factor formula for determining the flow of the starting sprinkler.   For more information about NFPA 13 sprinkler system design, check out the NFPA 13 Online Training Series. The training has been updated recently to reflect the most current 2022 edition of NFPA 13. Module 2 of this training provides users with a comprehensive overview of the calculations we discussed in this blog.