AUTHOR: Valerie Ziavras

Vertical opening

Types of Permissible Vertical Openings

The Life Safety Code, NFPA 101, aims to protect the life safety occupants by minimizing their exposure to fire, smoke, and its effects. One of the ways this is done is through building compartmentation. To limit the spread of fire, smoke, and its effects one of the base requirements of the Life Safety Code is that every floor that separates stories in a building must be constructed as smoke barriers. However, some openings in these smoke barriers are necessary for the functionality of the building while others are for convenience or aesthetics. These openings can provide a pathway for fire and smoke to travel vertically through the building. To minimize the spread of fire and smoke vertically throughout the building, openings in these separations are limited to those specifically identified in the Life Safety Code. Ultimately, they allow the effects of fire to impact occupants on other floors who would otherwise be protected if it weren’t for these openings. In addition to limiting the types of openings, the vertical openings must be protected to minimize the spread of the effects of fire. Pipe Penetrations and Expansion or Seismic Joints Pipes, cables, conduits, and similar items must run vertically through the building to allow utilities to reach all areas of the building. Similarly, vertical openings created by expansion or seismic joints are necessary for the structural integrity of a building. Any type of vertical openings created by pipe penetrations must be protected with a listed firestop system or device which must also limit the transfer of smoke. Expansion or seismic joints must be listed showing that it is designed to prevent the penetration of fire. Shafts Shafts are used for a variety of reasons, such as for elevators, pipes, mechanical equipment, and even stairs. Shafts must be separated from the building with fire-resistance rated walls and typically extend from the top of the building all the way to the bottom of the building. The fire-resistance rating of the walls will depend on if it is a new or existing shaft and the number of stories it connects. If the shaft does not extend through the entire building, then it must terminate at construction of equal or higher fire resistance rating. Atrium  Atria are a type of vertical opening that are used for convenience and/or aesthetics. They are some of the largest vertical openings you might see in a building and recognized by NFPA 101. An atrium is permitted to be open to any number of stories and can be located anywhere in the building.  The atrium must be separated from the remainder of the building with 1-hour fire-resistance rated walls. Glass walls are permitted to be used instead of the rated walls provided a number of other conditions are met. The entire building must be protected by a supervised automatic sprinkler system. Only low- or ordinary-hazard contents are permitted within the atrium. Additionally, atriums, other than existing, previously approved atriums, must have an engineering analysis that shows that the smoke layer interface stays a safe distance above the highest unprotected opening or the highest walking surface. If the engineering analysis shows that the smoke layer interface can’t be kept high enough, then a smoke control system is required. Communicating Space A communicating space is sometimes referred to as a “mini-atrium”. Although the protection scheme is different, they may look very similar. The major differences are the number of stories they connect and the location in the building. A convenience opening can only connect three or fewer adjacent stories (to connect three stories, at most two floors would have openings in them) with either the lowest floor or the next to the lowest floor of the communicating space being a street floor. Protecting occupants in a communicating space relies on the space either being open and unobstructed providing occupants with a high level of awareness of what is happening in the space, or the space must be open and have smoke detection. Smoke detection ensures occupants within the communicating space have an early indication of fire or other emergency condition and can react appropriately. The egress capacity within the communicating space must be sufficient for all occupants, on all levels within the communicating space, to egress at the same time and every occupant within the space must have access to at least one exit without having to travel vertically through the communicating space to get to one. Occupants not in the communicating must have access to at least one exit without having to travel through communicating space. The communicating space must be separated from the rest of the building by 1-hour fire-resistance rated walls unless the building is fully sprinklered. Lastly, the contents within the communicating space are limited to low-hazard contents unless there is an automatic sprinkler system, then the contents can be ordinary-hazard. All occupancies, with the exception of healthcare permit this type of vertical opening.     Allowable Locations for Communicating Spaces   Convenience Opening In some cases, for convenience or aesthetic purposes, building owners may want a vertical opening between fewer floors. Convenience openings are another vertical opening option. They connect two adjacent stories, piercing only one floor.  If travel is permitted within the convenience opening, it cannot be considered part of the required means of egress. The opening must be separated from other unprotected vertical openings and separated from corridors by construction that is equivalent to what the occupancy chapter requires for corridor wall separation. For new construction, if the occupancy does not require fire-resistance rated corridor separation then the convenience opening must be separated from the corridor by a smoke partition.  Convenience Stair Convenience stairs are permitted to connect no more than 4 contiguous stories for new construction. An example of a convenience stair opening would be if you had a four-story business occupancy that had unenclosed stairs that allowed for travel between all four floors. Although similarly named, the protection requirements for convenience stairs are different than the protection requirements for convenience openings and thus you are permitted to have more floors open to each other. Convenience stairs cannot serve as part of the required means of egress (exit access, exit, or exit discharge), the building must be protected with a supervised, automatic sprinkler system, and the opening has to be protected with closely spaced sprinklers and a draft stop as outlined in NFPA 13. When used in new construction, the size of the opening is limited to less than twice the horizontal projected area of the stairway. Two-Story Opening with Partial Enclosure A two-story opening with a partial enclosure is permitted in all occupancies. On one floor, the opening must be separated from the remainder of the floor by fire-resistance rated walls and a fire-protection rated door. On the other floor, the enclosure is open to the floor. This separation prevents the spread of fire and smoke on one of the two levels from spreading to the other floor. It is up to the designer to choose which floor the opening is separated from and which it is open to.   Two-Story Opening with a Partial Enclosure on the 2nd Floor Mezzanine A mezzanine is a partial floor level between stories. The mezzanine itself is not considered a story where it meets certain area limitations and openness requirements. Additional requirements such as supervised automatic sprinkler protection and access to exits are driven by the size and design of the mezzanine. Mezzanine Escalator There are a few options of how to protect a vertical opening created because of the presence of an escalator. One of the more common methods is to provide protection in accordance with NFPA 13 through the use of closely spaced sprinklers and a draft stop around the opening. Conclusion Vertical openings need to be properly protected in order to minimize the number of occupants on other floors that are exposed to fire, smoke, and its effects. Here, the high-level requirements for the more common types of vertical openings are provided. Section 8.6 of NFPA 101 provides additional details for how these openings need to be protected as well as requirements for some less common types of openings. 

The Basics of Sprinkler Thermal Characteristics

There are many different decisions that need to be made when it comes to designing a sprinkler system, such as what type of sprinkler system should be installed (check out this blog for more information on that topic), what type of piping should be used, and even which sprinkler should be selected. When manufacturers have well over a hundred different types of sprinklers it can be challenging to know which one to choose. Certain sprinkler characteristics will help determine which is an appropriate type for your specific situation. NFPA 13 Standard for the Installation of Sprinkler Systems identifies a number of sprinkler characteristics including thermal sensitivity, temperature rating, k-factor, installation orientation, water distribution characteristics, and special service conditions. While these are all important, I’m going to focus on two particular sprinkler characteristics, thermal sensitivity and temperature rating. Thermal Sensitivity The thermal sensitivity of a sprinkler measures how quickly the thermal element operates. Perhaps the most common way of measuring thermal sensitivity is the response time index (RTI). Sprinklers are then categorized into fast or standard response based on their RTI. The RTI is typically determined by conducting a plunge test in which a sprinkler is placed (plunged) into a heated laminar airflow within a test oven. Then, the operating time of the sprinkler, the operating temperature of the sprinkler’s heat-responsive element, the air temperature of the test oven, the air velocity of the test oven, and the sprinkler’s conductivity factor are used to calculate the RTI. Additional factors impact the response such as the temperature rating of the sprinkler, sprinkler position, fire exposure, and radiation. Category RTI (meters-second)1/2 [(ft-sec)1/2] Fast Response 50 or less (90 or less) Standard Response 80 or more (145 or more) There are also different types of fast response sprinklers. You may have heard of quick response or residential sprinklers. Both of these are fast response type sprinklers meaning they have an RTI of 50 meters-second1/2 or less, but they are considered different types of sprinklers because although their RTI is similar the performance characteristics and design parameters are different. RTI can also be expressed in (ft-sec)1/2 but the metric version is most common. While this is all important to understand, the real question is, what does this mean when selecting sprinklers? Certain situations require specific types of thermal sensitivity ratings per NFPA 13, but we are going to focus on the broader concept of why you may choose a fast response sprinkler over a standard response sprinkler or vice versa. It should be noted that a number of other factors will impact when and how quickly a sprinkler operates under true fire conditions. Variables such as ceiling height, spacing between sprinklers, ambient room temperature, and the distance the sprinkler is below the ceiling will all impact the time to operation. However, if all these elements are held constant, a fast response sprinkler would operate before a standard response sprinkler. In some situations, such as in a light hazard occupancy this is ideal. Since a low hazard occupancy has a low quantity and combustibility of contents, we expect the fire growth to be relatively slow when compared to other hazard classifications. Therefore, a fast response sprinkler will open earlier and be able to control the fire. In some situations, opening earlier is not ideal and therefore a standard response sprinkler is preferred, or even required. In certain storage applications, where fire growth is much faster, if fast response sprinklers are used additional sprinklers may be opened than the system was designed for. This could result in lower amounts of water and pressure flowing from each sprinkler resulting in less water over the actual fire and ultimately causing the sprinkler system to be ineffective in controlling the fire. If standard spray sprinklers were used, less sprinklers would operate, and this could provide enough time for those sprinklers to control the fire before others operate. Temperature Rating Looking closely at sprinklers with glass bulbs, you may have noticed that there are different color bulbs. The colors identify the temperature rating of the sprinkler. The temperature rating of the sprinkler selected needs to consider the maximum ambient ceiling temperature as well as the occupancy classification. If the maximum ambient ceiling temperature isn’t considered, it could result in accidental sprinkler operation since sprinklers are activated by heat. If the sprinkler does not have a glass bulb, then the frame arm, deflector or coating material will usually have some color indicating the temperature rating. zA Temperature classifications range from ordinary which has a temperature rating of 135-170OF (57-77OC) to ultra-high which has a temperature rating of 650OF (343OC). Typically, ordinary or intermediate which has a temperature rating of 175-225OF (79-107OC) sprinklers are required to be installed unless a certain situation calls for a higher temperature classification. Some examples of situations that require higher temperature ratings are sprinklers installed in commercial-type cooking equipment and sprinklers installed within certain distances of heat sources. Max Ceiling Temperature oF (oC) Temperature Rating oF (oC) Temperature Classification Glass Bulb Colors Color Code 100 (38) 135-170 (57-77) Ordinary Orange or Red Uncolored or Black 150 (66) 175-225 (79-107) Intermediate Yellow or Green White 225 (107) 250-300 (121-149) High Blue Blue 300 (149) 325-375 (163-191) Extra High Purple Red 375 (191) 400-475 (204-246) Very Extra High Black Green 475 (246) 500-575 (260-302) Ultra High Black Orange 625 (329) 650 (343 Ultra High Black Orange Conclusion At first glance, thermal sensitivity and temperature rating may seem like they address the same concern. However, they do not. Thermal sensitivity dictates how quickly a sprinkler will operate while temperature rating is based on the ambient ceiling temperature. In both cases though, it is important that all sprinklers in a given compartment have the same thermal sensitivity and the same temperature rating. Mixing can cause a phenomenon known as skipping. We expect the sprinkler closest to the fire to operate first. If that sprinkler alone isn’t able to control the fire, then we would expect the next closest sprinkler(s) to operate. This pattern would continue until enough sprinklers have opened to control the fire.   However, if different thermal sensitivities or temperature ratings are used, instead of the closest sprinklers operating, you could have a situation where a sprinkler closer to the fire does not operate and a sprinkler further away does. This is known as skipping and can have negative consequences on the performance of the system.     It should be noted that only a mix of ordinary- and intermediate-temperature sprinklers are permitted throughout a building unless a specific situation requires the use of a higher rated sprinkler, such as proximity to a heat source or high ambient ceiling temperatures.
A street with high rises

Occupancy Classifications in Codes

One of the most critical steps in applying NFPA 101, Life Safety Code, and other building and fire codes to a space is identifying the correct occupancy classification. The 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. While the majority of the NFPA developed codes and standards use occupancy classifications consistent with the Life Safety Code, including NFPA 5000, Building Construction and Safety Code, other organizations’ codes and standards may differ. This can create challenges for the designer when multiple codes and standards are applicable and enforced in a jurisdiction. Perhaps one of the more common scenarios is when both the International Building Code (IBC) and the Life Safety Code apply. Below is a table comparing the different occupancy classifications between the IBC and NFPA 101/5000. One thing to note is that although some of the occupancies seem to correlate obviously, there may be differences between details within the definitions, such as minimum number of occupants, that could result in a different classification. NFPA 101 and 5000 Occupancy Classification IBC Occupancy Classification Assembly Assembly (divided into subcategories A-1, A-2, A-3, A-4, A-5) Ambulatory Health Care Business Educational Educational Day Care Educational or Institutional Health Care Institutional (divided into subcategories I-1, I-2, I-3, and I-4) Detention and Correctional Residential Board and Care Institutional or Residential One- and Two-Family Dwelling Residential (divided into subcategories R-1, R-2, R-3 and R-4) Lodging or Rooming House Hotels and Dormitory Apartment Mercantile Mercantile Business Business Industrial Factory and Industrial (divided into subcategories F-1 and F-2) Storage Storage (divided into subcategories S-1 and S-2) No equivalent occupancy classification (see paragraph below for additional information) High Hazard (divided into subcategories H-1, H-2, H-3, H-4, and H-5) No equivalent occupancy classification (see paragraph below for additional information) Utility and Miscellaneous   Ambulatory Health Care One major difference between the NFPA 101/5000 occupancy classifications and the IBC classifications is the ambulatory health care occupancy classification. It is important to understand what types of facilities we are discussing before we get into how these are classified differently. Ambulatory health care occupancies per the Life Safety Code are those occupancies in which four or more patients are being treated simultaneously and are incapable of self-preservation because of (1) the treatment; (2) anesthesia; or (3) the nature of the injury/illness. Although not a separate occupancy classification, the IBC does have a definition for “Ambulatory Care Facility” which closely resembles the NFPA ambulatory health care occupancy. Per the IBC, these types of facilities would be considered business occupancies. NFPA 101 and 5000 create a distinction between business occupancies and ambulatory health care facilities based on the occupants’ ability of self-preservation. Therefore, these types of facilities would not be considered business occupancies but would be considered ambulatory health care occupancies per NFPA. It is worth mentioning that per NFPA a traditional doctor’s office or an urgent care center where patients are still capable of self-preservation would be considered business occupancies. Educational and Day Care NFPA 101 separates day care occupancies from educational occupancies. The NFPA and IBC definitions for educational occupancies are fairly similar. At first glance it may seem like some occupancies that would be classified as educational per the IBC would actually be day care occupancies per NFPA. However, when you look more closely at Chapter 16 and 17 of NFPA 101 you find that occupancies in which the primary purpose is education for children 30 months of age or older must comply with the educational occupancy requirements. It should be noted that prior to the 2021 Edition, the age was 24 months. While the educational definitions are closely aligned between NFPA and IBC, the major difference is the NFPA occupancy classification of day care. There are two main categories of day cares, those providing services for children and those providing services for adults. Instead of calling these day care occupancies, the IBC would classify child day cares serving children under two and a half years old and adult day cares as institutional occupancies. There is one exception to this. A childcare facility with more than 5 but less than 100 clients two and a half years of age or younger, and located on the level of exit discharge, is classified as an educational occupancy per the IBC. Institutional The institutional occupancy group in the IBC consists of four different categories: I-1, I-2, I-3, and I-4. These subcategories are based on anticipated occupant characteristics and there are similar occupancy classifications found in NFPA 101/5000. However, in the NPFA codes and standards these are treated as individual occupancy classifications and not as subcategories of a broader classification. Even with the sub-categories, the occupancy classifications do not always obviously align between NFPA and IBC. The table below summarize how the NFPA occupancy classifications would most likely fall into the IBC institutional subcategories.   Closer Look at how NFPA Occupancy Classifications Align with IBC Residential Subcategories NFPA IBC Notes Day Care I-4 Depends on number of occupants, age of occupants, and location of occupants in relationship to the level of exit discharge Educational Health Care   I-2 N/A Detention and Correctional I-3 N/A Residential Board and Care I-1 Depends on the number of occupants   R-3 R-4 When starting with the IBC institutional subclassification determining the NFPA occupancy classification is more straightforward. Remember though, it is important to always verify the actual definitions and minimum number of occupant requirements before selecting the appropriate occupancy classification. The table below shows the potential NFPA occupancy based on the IBC institutional subcategory.   IBC NFPA I-1 Residential Board and Care I-2 Health Care I-3 Detention and Correctional I-4 Day Care Residential The residential occupancy group in the IBC consists of four different categories: R-1, R-2, R-3, and R-4. These subcategories are based on anticipated occupant characteristics and there are similar occupancy classifications found in NFPA 101/5000. However, in the NPFA codes and standards these are treated as individual occupancy classifications and not as subcategories of a broader classification. Even with the sub-categories, the occupancy classifications do not always obviously align between NFPA and IBC. The table below summarize how the NFPA occupancy classifications would most likely fall into the IBC residential subcategories.   Closer Look at how NFPA Occupancy Classifications Align with IBC Residential Subcategories NFPA IBC Notes One- and Two-Family Dwelling R-3 N/A Lodging or Rooming House R-1 Depends on the number of occupants R-3 Hotels R-1 Depends on the nature of the occupants (transient or not) R-2 Dormitories R-2 N/A Apartment R-2 N/A Residential Board and Care R-3 Depends on the number of occupants   R-4 Institutional If you are starting with the IBC residential subclassification and trying to determine the NFPA occupancy classification, it is not as straightforward. The IBC uses terminology not found in NFPA 101 or 5000 and creates the subclassification groups based on different characteristics of how the space is being used, such as the number of occupants. The table below shows how many potential NFPA occupancies you could have per each IBC residential subcategory.   Closer Look at how IBC Residential Subcategories Align with NFPA Occupancy Classifications IBC NFPA Notes R-1 Lodging or Rooming House Depends on the number of occupants Hotel R-2 Apartment Depends on the nature of the occupants (transient or not) Hotels Dormitories R-3 One- and Two- Family Dwelling Depends on (1) number of occupants and/or outsiders and (2) if residents are receiving personal care services Lodging or Rooming House Residential Board and Care R-4 Residential Board and Care N/A High Hazard One of the major differences between how NFPA 101/5000 and the IBC address occupancy classification is how they handle areas and spaces where high hazard materials are present. The IBC has a separate occupancy classification for areas or spaces that manufacture, process, generate, or store “materials that constitute a physical or health hazard” in amounts larger than what is permitted in control areas. NFPA, on the other hand, does not create a separate occupancy classification, instead, there are provisions for high hazard contents that must be followed, regardless of the occupancy whenever applicable. High hazard contents are “those that are likely to burn with extreme rapidity or from which explosions are likely.” Additionally, there are subclassifications of certain occupancies, such as storage and industrial, for those that store or use high-hazard contents. Within the occupancy chapter, additional requirements apply based on the high-hazard classification. NFPA 5000 has a chapter with additional requirements based on the presence of high hazard contents. Again, this does not change the occupancy classification itself but does require additional fire protection and/or life safety features because of the increased hazard of the space. Utility and Miscellaneous Another major difference between how NFPA 101/5000 and the IBC address occupancy classification is the Utility and Miscellaneous occupancy classification the IBC has. There is no equivalent in the NFPA occupancy classification. In the IBC, this group is used for structures such as barns, sheds, and towers. While there is no separate occupancy group for these in the NFPA classifications, these structures would still be assigned an occupancy classification. Depending how the space is actually used, storage, industrial, or business are potential examples of appropriate occupancy classifications. Additionally, NFPA 101 and 5000 have requirements for “Special Construction” and “High-Rise” buildings. Instead of changing the occupancy classification when traditional occupancies are placed in unique buildings or are in unusual surroundings, there are requirements that modify the base occupancy requirements to accommodate for these unusual surroundings or structures and the risks associated with them. Conclusion The application of occupancy classifications between different organizations’ codes and standards is not always straight forward. Therefore, when working with multiple codes, you must consider the specific building and the occupant characteristics of that space. Since different occupant thresholds and occupant characteristics are used for different organizations’ codes and standards, you can’t always generalize how the occupancy classifications align. Hopefully, the above tables provided some insight and at least a starting point when trying to determine how the occupancy classifications relate.
Sprinkler pipe

Sprinkler System Basics: Types of 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. Wet Pipe Systems Wet pipe sprinkler systems are the most common. In this system the sprinkler piping is constantly filled with water. When the temperature at the ceiling gets hot enough the glass bulb or fusible link in a sprinkler will break. Since the system is already filled with water, water is free to flow out of that sprinkler head. Contrary to what Hollywood would have you think, not all sprinkler heads will operate at once in this type of system. The temperature around that specific sprinkler head needs to be high enough to break the glass bulb or fusible link that is holding water back. Once that happens, water will immediately start flowing from only that head. Wet pipe sprinkler systems are the most reliable and cost effective. Therefore, they should be the first type considered when selecting a sprinkler system. However, there are times when a wet pipe sprinkler system may not be appropriate. One of the major factors in determining if a wet pipe system can be used is the temperature of the space to be protected. Will all areas of the building where the sprinkler piping is located be conditioned to at least 40OF (4OC) or greater?  If the answer is yes, then there is no risk for the water in the piping to freeze and a wet system is the preferred method. However, if the answer is no, an additional study may need to be done to determine if an engineer can prove that although the temperature could drop below 40OF (4OC) it will never drop low enough for the water to freeze. If the temperature of the space cannot be guaranteed to eliminate the risk of freezing water, then a different system type should be chosen. Dry Pipe Systems Dry pipe systems are very similar to wet pipe systems with one major difference. The pipe is not constantly filled with water. Instead, the water is held behind a dry pipe valve usually some distance away from where the sprinklers are located. Like a wet pipe system, when the temperature at the ceiling becomes hot enough, the glass bulb or fusible link of the sprinkler breaks. However, in this case, water isn’t immediately available because the pipe is not water filled. Instead, air is released from the now open sprinkler head. This creates a drop in pressure causing the dry pipe valve to open and water to fill the system. Water will then flow from the open sprinkler head. Since there is a delay between sprinkler operation and water flow, the size of dry pipe systems is limited. The size limitation is intended to minimize the amount of time water delivery is delayed. A dry pipe system is a great option for unconditioned spaces, or locations where the temperature of the space cannot be guaranteed to be high enough to prevent water in the system from freezing. It is important to note that a least the portion of the building where the water comes in and the dry pipe valve is located will need to have temperatures hot enough to prevent freezing. Preaction Systems Of all the sprinkler system types perhaps the most complicated is the preaction system. There are three different types of preaction systems, a non-interlock system, a single interlock system, and a double interlock system. The main difference between preaction systems and wet and dry pipe systems is that a specific event (or events) must happen before water is released into the system. This might sound similar to a dry pipe system, but the differences lie in what event triggers the release of the water: For a non-interlock system: the operation of detection devices OR automatic sprinklers For a single interlock system: the operation of detection devices For a double interlock system: the operation of detection devices AND automatic sprinklers To better explain how these types of systems work, we’ll walk through an example using a room that is protected with sprinklers fed from a preaction system. In addition to sprinklers, the room has complete automatic heat detection. Typically, the detection system, will have a lower temperature rating than the sprinklers. This will help ensure that the detection system activates before a sprinkler head operates. In this case, heat detectors that have a rating of 135OF will serve as our detection system, and the sprinklers will have a temperature rating of 165OF. In a non-fire event, such as accidental damage to a sprinkler head that results in the glass bulb breaking, the system would fill with water in a non-interlock system, and water would flow from the broken sprinkler head. The same situation in a single interlock preaction system would not result in waterflow because the broken glass bulb will not trigger the system to be filled with water. Only the operation of detection devices will result in a water filled system for a single interlock system. In the same room, the non-interlock and single interlock systems operate very similarly if there was a fire event. The heat detectors should activate first since they have a lower temperature rating. For both a non-interlock and a single interlock system, the activation of the heat detectors would result in the system filling with water. Then, if the temperature continues to rise, a sprinkler will operate. Since the “event”, heat detection, has already happened, the system is filled with water, and we would expect it to act like a traditional wet pipe system. In this same situation, a double-interlock system will not fill with water upon the activation of the heat detection. Instead, the system will only fill with water after the activation of the heat detection system and the operation of a sprinkler head. Therefore, a delay in water delivery similar to what is seen for dry pipe systems will occur. For this reason, double interlock preaction systems have similar size restrictions as dry pipe systems, whereas non-interlock and single interlock are just limited to 1000 sprinkler heads per preaction valve. Additional considerations, other than temperature, may lead to the selection of another type of permitted sprinkler system. In some cases, there may be a desire to minimize the risk of water damage or to prevent the accidental filling of the system. In these cases, a single or double interlock system may be the preferred option. A single interlock system may be beneficial in museums, computer rooms, or similar settings where water damage is a concern. This would eliminate the risk of accidental water flow if a sprinkler head was damaged. Although NFPA 13 does not specifically prohibit the use of double interlock systems in these types of spaces, the double interlock preaction system was not developed for these situations. It was intended for use in freezer storage warehouses, or in similar situations where the accidental presence of water in the piping system will lead to expensive remediation. It is important to consider the delay in water delivery that occurs with a double interlock preaction system before selecting that system type. If it is used in a museum or similar type of environment, the delay in water delivery would allow the fire to continue to grow which could result in additional sprinklers opening. In turn, this could increase the water damage and result in a larger portion of the building being involved. Deluge systems are similar to preaction systems in that they use another type of detection for operation. However, the biggest difference is that deluge systems use open sprinklers or nozzles. Instead of getting water flow from individual heads that have operated, once water fills the system, water will flow from every sprinkler head. Much like a preaction system, a deluge valve will keep water from filling the system until the operation of another type of detection system, such as smoke detection. Once that detection system is activated, water not only fills the system but flows from the open sprinklers or nozzles. Another consideration in the selection of the type of sprinkler system is the level of hazard being protected. If protecting an area of very high hazard, such as aircraft hangers, a deluge system may be the most suitable. Each system type has its own unique benefits. It is important to consider the pros and cons of each system type when selecting which sprinkler system is appropriate for your specific environment. An entire building may be protected with a combination of systems. For example, one of the more common designs in the Northeast is to protect the portions of the building that are conditioned with a wet pipe system and to use dry pipe systems in the attic and other unconditioned areas. Combining different types of systems for full building protection allows the designer to consider each unique environment and apply the most appropriate system type to that space without sacrificing what is best for other areas of the building.

Additive Manufacturing (3D Printing)

I recently came across an article about the first 3D printed house hitting the market in New York. While I’ve seen a lot of information regarding the benefits of 3D printing structures, mainly that it less expensive and faster than traditional construction methods, this was the first time I had seen a house that was actually 3D printed and being sold. It reminded me how quickly the 3D printing industry is expanding. The most recent edition of NFPA 1, Fire Code includes new language related to 3D printing or, more specifically, additive manufacturing.  One major distinction between the article and the language in the Fire Code is that the article is talking about structures that are 3D printed where as the NFPA 1 language addresses buildings that house additive manufacturing operations. Perhaps, as 3D printed structures become more popular the codes and standards may need to address unique requirements for them. Will there be special considerations when inspecting these types of structures, or will there be a limitation on the types of materials that can be used to print structures? Right now, the focus of requirements in the Fire Code is on protecting buildings that conduct additive manufacturing operations. Although you may have heard the term “3D printing” the Fire Code addresses “additive manufacturing.” Sometimes these are used interchangeably, but there is a difference. Additive manufacturing is the more inclusive term that encompasses all types of manufacturing that produce a product by adding material. Traditional manufacturing methods produce a product by removing material. The process starts with a block of material and pieces are removed and shaped until the desired shape is achieved. Here you can see how nails are made in a traditional manufacturing process. In additive manufacturing the process starts with nothing and material is added one thin layer at a time. 3D printing is one subset of additive manufacturing, but there are other types such as direct metal laser melting.  The Fire Code has two separate sets of requirements for additive manufacturing based on the associated hazard: industrial additive manufacturing and nonindustrial additive manufacturing.   Industrial Additive Manufacturing Industrial additive manufacturing processes are those operations that meet one of the following conditions: Use combustible powders or metals Use an inert gas supply Have a combustible dust collection system Create a hazardous electrical classification area outside of the equipment Nonindustrial Additive Manufacturing Nonindustrial additive manufacturing processes are those operations that meet all of the following: Do not use an inert gas supply Do not have a combustible dust collection system Do not create a hazardous electrical classification area outside of the equipment Differences in Requirements The use of combustible powders or metals, the use of an inert gas supply, or the creation of a hazardous electrical classification area outside of the equipment results in a higher level of hazard anticipated with industrial additive manufacturing than with nonindustrial additive manufacturing. Therefore, the requirements for industrial additive manufacturing and nonindustrial additive manufacturing are significantly different.  Location of Additive Manufacturing Nonindustrial additive manufacturing is permitted in all occupancy groups whereas industrial additive manufacturing is only permitted to be conducted in the occupancy groups associated with the manufacturing operations and as permitted by the maximum allowable quantity tables in NFPA 400. The fire and explosion hazards associated with industrial additive manufacturing are more aligned with the hazards you would see in a traditional manufacturing setting. However, many of those same hazards will not be found in nonindustrial additive manufacturing because of the differences in the operations. Therefore, those operations are permitted in a wider range of occupancies. Printing Powders The nonindustrial additive manufacturing operations are only permitted to use plastic filament production materials that are listed with the 3D printer and that are identified in the manufacturer’s instructions. The powders used in industrial additive manufacturing must be tested for combustibility in accordance with NFPA 484, Standard for Combustible Metals or NFPA 652, Standard on the Fundamentals of Combustible Dust. For industrial additive manufacturing operations additional requirements may need to be followed depending on the material used for production. For example, if a combustible, nonmetallic powder is used, then the operation must also comply with Chapter 40 of NFPA 1 and NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids. Since these types of combustible materials are not permitted in nonindustrial additive manufacturing there are no similar requirements for those types of operations.  Gas Detection Industrial additive manufacturing processes that use inert gasses must have a gas detection system in all indoor areas where the inert gas is present. The gas sensors must be provided in areas where the gas is expected to accumulate and other locations where the AHJ requires them. The system must activate a supervisory audible and visible alarm upon detection of inert gas at the 8-hour time-weighted average concentration. There must also be an audible and visible alarm within the room or immediate area where the system is located and must automatically shut off the flow of the inert gas to the 3D printing equipment when the system detects inert gas at the threshold limit value-short-term exposure limit concentration. There are no comparable requirements for nonindustrial additive manufacturing since those processes are not permitted to use inert gasses. This summarizes the major differences between the two types of additive manufacturing addressed in the Fire Code. For specific details, you can view chapter 46 in NFPA 1. This new chapter provides a starting point for a technology that is changing rapidly and gaining in popularity every day.  Have you started seeing additive manufacturing in your jurisdictions? What are some of the challenges you’ve faced when it comes to this technology?
Fire alarm

Low Frequency Fire and Smoke Alarms

The optimal sound and sound level for fire and smoke alarms has long been debated. The hope is that the right sound will be recognizable by building occupants and evoke the immediate desired response of evacuation. Beginning July 1, 1996, NFPA 72, National Fire Alarm and Signaling Code required that the building evacuation signal be the temporal-three sound. Typically, the temporal-three sound is produced at a high frequency tone of about 3150 Hz. Research continued on the optimal sound and further revisions were made in the 2010 edition of NFPA 72. Low frequency 520 Hz alarms were required for single and multiple station alarms, smoke alarms not connected to a building fire alarm, where the occupants have mild to severe hearing loss. This is because research over the last 20 years has shown that these low frequency alarms are more effective at waking sleeping occupants than the traditional alarm. In particular, the low frequency alarm is more effective for those in high-risk categories, such as children, elderly, those with hearing impairments, and those under the influence of alcohol. The 2013 edition of NFPA 72 broadened the use of low frequency alarms by requiring all audible appliances initiated by the building fire alarm that are provided in sleeping areas to wake sleeping occupants to be a low frequency 520-Hz alarm. As you can see, NFPA 72 only mandates the use of low frequency 520 Hz alarms for audible alarms, initiated by the building fire alarm system, in areas where the alarm is intended to wake sleeping occupants and only for audible alarms initiated by smoke alarms, not initiated by the building fire alarm system, in sleeping areas where occupants have mild to severe hearing loss. Changes to the 2021 edition of NFPA 101, Life Safety Code strive to make use of low frequency alarms more consistently throughout all sleeping areas. The changes require that, where the occupancy chapter mandates their use, audible alarms in sleeping rooms initiated by the building fire alarm system and audible alarms in sleeping rooms initiated by the activation of a smoke alarm, not the building fire alarm system, must result in a low frequency 520 Hz alarm. Two of the residential occupancy chapters in NFPA 101, new hotels and dormitories and new apartment buildings now require the use of low frequency alarms for audible notifications activated by both smoke alarms and the building fire alarm system. In summary, the difference between the NFPA 72 requirements and the 2021 NFPA 101 requirements is that NFPA 101 now requires, where mandated by the occupancy chapter, that all audible alarms in sleeping areas initiated by smoke alarms, not the building fire alarm system, be a low frequency 520 Hz alarm regardless of the hearing capabilities of the occupants in that sleeping room. NFPA 72 would only require low frequency alarms in those areas if the occupants had mild to severe hearing loss. There has been a lot of research related to the effectiveness of different alarms for notifying occupants of an emergency situation. One such report was published in 2007 by the Fire Protection Research Foundation, Optimizing Fire Alarm Notification for High Risk Groups. This research project began by creating a vulnerability matrix and then prioritized three vulnerable groups: 1) people under the influence of alcohol impairment; 2) people with hearing impairments; and 3) people in public spaces. Different notification technologies were then tested with these groups. Some technologies were omitted from this study because previous research and the challenges associated with ensuring the occupants received these notifications. These technologies included smell-based (olfactory-based) notifications, technologies that require the movement of air, and existing “one bit” signals. Additionally, electric shock notification was omitted because of ethical concerns. The findings of this research for those under the influence of alcohol and for those people with hearing impairments was consistent with previous work. The low frequency alarms were more effective for waking sleeping occupants. One of the challenges with low frequency 520 Hz alarms is that they require additional electrical power which has made the development of low frequency battery-operated alarms difficult. The Fire Protection Research Foundation conducted another project, Audible Alarm Signal Waking Effectiveness: Literature Review. Currently, there is no listed smoke alarm capable of emitting that sound available on the market. However, there are a number of alternative solutions. One option is to use smoke detectors with integral sounder bases, another option is to use fire alarm system horns, and another option is to connect speakers to an in-building fire alarm emergency voice alarm communication (EVAC) system. Hopefully, there will soon be a commercially available smoke alarm capable of emitting the low frequency sound that has proven to be more effective in waking high risk groups. Until then, an alternative design approach would need to be used.

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