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'''Fire compartmentation''' is the division of a building into firecells or compartments enclosed by fire-resisting construction. Its purpose is to limit the spread of fire, smoke and heat between those spaces and to preserve required functions for occupants and firefighters. It uses walls, floors, doors, dampers, firestops and other details as one separating system.<ref name="CVM2-64">Ministry of Business, Innovation and Employment (2025), p. 64.</ref><ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref>
'''Fire compartmentation''' is the division of a building into spaces separated by construction intended to restrict the spread of fire and its effects. Walls, floors, closures and protected penetrations work together as a boundary. Its performance depends on maintaining the required structural, integrity and heat-transmission functions under the relevant exposure.<ref name="KH_1-155">Kodur and Harmathy (2002), p. 1-155.</ref><ref name="N_F-24">Iqbal and Salley (2004), p. F-24.</ref><ref name="CVM_64">Ministry of Business, Innovation and Employment (2025), p. 64.</ref>


A firecell is any space or group of contiguous spaces enclosed by fire separations, external walls, roofs and floors. Internal floors between firecells are themselves fire separations. This makes compartmentation a three-dimensional arrangement rather than a collection of unrelated walls.<ref name="CVM2-64" />
The separation is not defined by a wall alone. Doors, ventilation openings, service penetrations, junctions and supporting construction can determine how a fire reaches another space. Some routes exist from the outset, while others develop through opening, damage or structural failure. Concealed voids and shafts can connect spaces beyond the room of origin.<ref name="IFEG_1.6-6_1.6-8">Australian Building Codes Board et al. (2005), pp. 1.6-6–1.6-8.</ref>
[[File:fse-fire-compartmentation-v1.svg|thumb|upright=1.5|alt=Firecell bounded by walls, floor, roof, fire door, damper and penetration seals.|A firecell is a complete separating system. Based on Ministry of Business, Innovation and Employment (2025), p. 64.]]


Compartmentation can delay fire spread and provide time for detection, evacuation, suppression and structural response. It does not guarantee containment, because openings, penetrations, conduction and failure of individual components can defeat the intended boundary.<ref name="IFEG-1.6-7" /><ref name="Rockett-Milke-1-29">Rockett and Milke (2002), p. 1-29.</ref>
Smoke movement adds a further consideration because intact construction can still contain leakage paths. Pressure differences drive flow through those paths and through open doors. Compartmentation consequently interacts with evacuation, ventilation and smoke control, as well as the fire resistance of its materials and assemblies.<ref name="Kl_4-277_4-279">Klote (2002), pp. 4-277–4-279.</ref><ref name="IFEG_1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref>


== Separating elements ==
== The compartment boundary ==


[[Fire resistance]] supplies the performance criteria for compartment boundaries. Structural adequacy, integrity and insulation must be maintained as applicable for the required duration. C/VM2 reports these in that order, with durations determined from standard tests or verified calculation methods.<ref name="CVM2-64" />
A compartment is a volume separated from other spaces by construction intended to restrict fire effects, and its boundary can include walls, floors, a roof and closures within those elements. New Zealand's C/VM2, second edition of 2025, calls the enclosed volume a firecell. Its definition allows contiguous spaces on the same or different levels, rather than limiting a firecell to one room.<ref name="CVM_64" />


A [[Fire wall]] separates buildings or subdivides a building to prevent fire spread through fire resistance and, where required, structural stability. Its ends, roof junctions and connections must also be detailed so that fire cannot bypass the main wall. A wall is effective only as part of that complete boundary.<ref name="NUREG-1805-17-7">U.S. Nuclear Regulatory Commission (2005), p. 17-7.</ref>
The boundary is therefore a complete system of construction and protected openings. The definition of a fire barrier in NUREG-1805 includes supports, penetration seals, closures, doors and dampers alongside walls and floors. That report was prepared for the United States nuclear regulatory inspection programme. Its terminology usefully identifies the interacting components without establishing requirements for every other building type.<ref name="N_F-24" />


A [[Fire door]] protects an opening in a fire-resistive wall and has a specific fire resistance rating. It normally closes and latches automatically if it is not already closed, while still allowing occupants to pass. Door operation, seals, frames and hardware are part of the opening's performance.<ref name="CVM2-64" /><ref name="NUREG-1805-C-9">U.S. Nuclear Regulatory Commission (2005), p. C-9.</ref>
[[File:fse-fire-compartmentation-v1.svg|thumb|upright=1.5|alt=Firecell bounded by walls, floor, roof, fire door, damper and penetration seals.|A firecell is a complete separating system. Based on Ministry of Business, Innovation and Employment (2025), p. 64.]]


A [[Fire damper]] automatically seals an air-distribution opening to resist heat and flame. It preserves the rating of the wall, partition or floor penetrated by the duct, using a fusible link or remote activation signal. Both its fire resistance and its airflow closure behaviour matter.<ref name="NUREG-1805-F-19">U.S. Nuclear Regulatory Commission (2005), p. F-19.</ref>
[[Fire resistance]] describes how the construction maintains specified functions under an exposure. Those functions include structural adequacy, integrity and insulation where applicable: the first concerns load-bearing performance, the second passage of flames or hot gases, and the third heat transmission. A compartment boundary can lose one function while retaining another.<ref name="KH_1-155" /><ref name="M_4-210_4-211">Milke (2002), pp. 4-210–4-211.</ref><ref name="CVM_64" />


[[Firestopping]] seals penetrations and narrow gaps around services and joints. C/VM2 requires the fire stop to have a rating no less than the fire separation in which it is installed. A continuous barrier therefore needs appropriate products and installation for its orientation and use.<ref name="CVM2-64" /><ref name="CVM2-13">Ministry of Business, Innovation and Employment (2025), p. 13.</ref>
A [[Fire wall]] is one form of separating construction, but its precise role depends on the governing framework. Iqbal and Salley distinguish a wall intended to remain stable through an uncontrolled fire from a barrier used with other protective measures. That distinction belongs to their discussion of United States practice. It does not make every internal partition a structurally independent fire wall.<ref name="N_17-7_17-8">Iqbal and Salley (2004), pp. 17-7–17-8.</ref>


== Fire spread and failure modes ==
== Routes by which fire can spread ==


[[Fire spread]] can occur through openings, radiation, direct flame contact, burning debris and conduction through solid boundaries. Compartmentation addresses these pathways differently. A barrier that stops direct flame can still transmit enough heat to ignite material on its unexposed side.<ref name="IFEG-1.6-7" /><ref name="VR-5.1">Van Rossum (2027), §5.1.</ref>
[[Fire spread]] between compartments can follow openings that already exist or openings created during the fire, and the 2005 International Fire Engineering Guidelines treat both categories explicitly. Doors and windows may be open initially, while glazing breakage or damage can create further routes. The state of each route can change as the event develops.<ref name="IFEG_1.6-1">Australian Building Codes Board et al. (2005), p. 1.6-1.</ref><ref name="IFEG_1.6-6">Australian Building Codes Board et al. (2005), p. 1.6-6.</ref>


Conductive failure occurs when sufficient heat passes through an intact barrier to meet a failure criterion. There may be no cracks or collapse, so visual integrity alone does not demonstrate protection. The combustibles and their arrangement on the receiving side must be included in the assessment.<ref name="IFEG-1.6-7" /><ref name="Rockett-Milke-1-29" />
An opening can also result from missing or inadequate sealing around services. Pipes, cable trays and ventilation ducts cross boundaries to perform normal building functions. Those crossings need their own representation in the separating system. A sound wall surface does not describe the behaviour of an unprotected opening through it.<ref name="IFEG_1.6-6" /><ref name="N_17-8">Iqbal and Salley (2004), p. 17-8.</ref>
[[File:fse-fire-compartmentation-v2.svg|thumb|upright=1.5|alt=Three panels: heat through an intact wall, cracks with smoke and a collapsed wall.|Compartment boundaries can fail thermally, through integrity or through stability. Based on Australian Building Codes Board et al. (2005), p. 1.6-7.]]


Loss of integrity involves cracks, fissures and failed firestopping, allowing flames and hot gases through. Loss of stability involves collapse of the barrier and creates a much larger opening. These modes can occur at different times and should be evaluated separately.<ref name="IFEG-1.6-7" />
Concealed spaces can connect locations that appear separate in an occupied room, and the guidelines identify ceiling voids, hollow construction, spaces under floors and spaces behind external cladding. Shafts and large service ducts can provide vertical routes. In the analysis, these spaces become further enclosures with their own connections and boundaries.<ref name="IFEG_1.6-6" />


Openings change with occupancy and firefighting. Doors can open for evacuation, glazing can break and ventilation components can operate, altering both fire spread and oxygen supply. Compartmentation must therefore be assessed as a changing system, not as a fixed drawing of closed boundaries.<ref name="CVM2-14">Ministry of Business, Innovation and Employment (2025), p. 14.</ref><ref name="IFEG-1.6-7" />
The route can also pass outside the building before re-entering another space, and the guidelines discuss flames projecting from windows, radiation and burning debris. Adjacent buildings can be exposed through openings or external surfaces. Compartmentation therefore cannot be assessed solely by tracing internal partition lines on a floor plan.<ref name="IFEG_1.6-5_1.6-7">Australian Building Codes Board et al. (2005), pp. 1.6-5–1.6-7.</ref>


== Passive protection as a system ==
[[File:fse-fire-compartmentation-v3.svg|thumb|upright=1.5|alt=Fire and smoke passing through a door, duct, cable penetration, cavity and wall end.|Openings and junctions can bypass a fire-rated wall. Based on Australian Building Codes Board et al. (2005), p. 1.6-7 and Iqbal and Salley (2004), p. 17-8.]]


[[Passive fire protection]] prolongs fire resistance without manual, mechanical or other initiation, replenishment or sustainment during the incident. Compartmentation is a central example because walls and normally closed barriers perform in their normal orientation. Other passive measures include insulation, coatings and noncombustible construction.<ref name="NUREG-1805-F-44">U.S. Nuclear Regulatory Commission (2005), p. F-44.</ref>
== Thermal, integrity and stability failures ==


The complete assembly determines performance. A strong wall can be undermined by an unprotected penetration, an open door or an unsuitable damper, while a well-detailed system can delay spread without looking unusual in normal use. Product choice and installation are therefore inseparable from the rating.<ref name="CVM2-13" /><ref name="White-4-259">White (2002), pp. 4-259–4-260.</ref>
Heat can pass through an intact boundary by conduction. The unexposed surface may then become hot enough to breach an insulation criterion or ignite nearby material under suitable conditions. This mechanism does not require a visible hole. The thermal properties, thickness and exposure history influence the resulting temperature distribution.<ref name="IFEG_1.6-7" /><ref name="VR_5.2">Van Rossum (2027), §5.2.</ref>


Active systems can complement compartmentation by detecting and suppressing fire, but they do not remove the need for a sound boundary. A fire barrier can be intended to work together with sprinklers, while a fire wall may be intended to remain stable and uncompromised during an uncontrolled fire. These roles should not be confused.<ref name="NUREG-1805-17-7" /><ref name="CVM2-64" />
Loss of integrity introduces a path through the boundary. Cracks, fissures and failed penetration protection can permit hot gases or flames to pass. Whether adjacent material ignites depends on its location and response to the exposure. The International Fire Engineering Guidelines distinguish this physical sequence from a simplified analysis that equates barrier failure with spread.<ref name="IFEG_1.6-6_1.6-7">Australian Building Codes Board et al. (2005), pp. 1.6-6–1.6-7.</ref>


Fire compartmentation also supports other passive goals. It can protect structural members, preserve safe paths and limit smoke movement, but each has its own criteria and timescale. A single rating cannot demonstrate all of these without the relevant assessment.<ref name="IFEG-1.6-3">Australian Building Codes Board et al. (2005), p. 1.6-3.</ref><ref name="CVM2-14" />
Loss of stability means that the barrier or its supporting construction can no longer remain in place, so a wall can fail because another structural element supporting it fails. The guidelines identify this dependency explicitly. The endurance of an isolated wall specimen is therefore not sufficient evidence for a boundary whose support fails earlier.<ref name="IFEG_1.6-7_1.6-8">Australian Building Codes Board et al. (2005), pp. 1.6-7–1.6-8.</ref>


== Openings and penetrations ==
[[File:fse-fire-compartmentation-v2.svg|thumb|upright=1.5|alt=Three panels: heat through an intact wall, cracks with smoke and a collapsed wall.|Compartment boundaries can fail thermally, through integrity or through stability. Based on Australian Building Codes Board et al. (2005), p. 1.6-7.]]
 
Service penetrations create potential weak points for flames, smoke and heat. Cables, pipes, ducts and trays require seals appropriate to the barrier and the service arrangement. Unsealed or unsuitable penetrations can allow a fire to move around an otherwise effective compartment wall.<ref name="NUREG-1805-F-28">U.S. Nuclear Regulatory Commission (2005), p. F-28.</ref><ref name="CVM2-13" />
[[File:fse-fire-compartmentation-v3.svg|thumb|upright=1.5|alt=Fire and smoke passing through a door, duct, cable penetration, cavity and wall end.|Openings and junctions can bypass a fire-rated wall. Based on Australian Building Codes Board et al. (2005), p. 1.6-7 and U.S. Nuclear Regulatory Commission (2005), p. 17-7.]]
 
Fire walls also need protected ends and roof junctions. NUREG-1805 lists fire-resistant exterior wing walls and a parapet extending through and above the roof deck as ways to prevent spread around the wall. Pipes, conduits and cables may be routed to floor level to reduce damage if the structure on either side collapses.<ref name="NUREG-1805-17-7" />
 
Concealed spaces need attention because they can connect compartments without obvious openings. Cavity barriers close openings within those spaces against fire and smoke spread. Their location, integrity and relationship with the main fire separations must be assessed.<ref name="CVM2-49">Ministry of Business, Innovation and Employment (2025), p. 49.</ref>
 
Fire doors and smoke control doors need correct operation during evacuation. C/VM2 assumes self-closing doors are closed except when being used, allowing three seconds per occupant at low load and continuous opening during queuing. This changes the boundary during the very period when protection is needed.<ref name="CVM2-14" />
 
== Fire engineering and evacuation ==
 
Compartmentation can preserve tenable conditions in adjacent spaces long enough for evacuation. Fire models compare the time available for escape with the time occupants need, and the boundary's condition affects both smoke spread and fire growth. ASET analysis includes only those separations and closures needed to demonstrate safe evacuation.<ref name="CVM2-14" />


Fire spread and barrier-failure times can also become inputs to new compartment design fires, evacuation and firefighting assessments. The analysis is therefore sequential: one compartment's conditions determine when the next becomes hazardous. A building-wide model must preserve those links.<ref name="IFEG-1.6-3" />
These mechanisms can interact during the same fire. An opening can change ventilation as well as permit spread into another enclosure. Structural loss can damage several boundaries together. The analysis therefore follows changes in the building and exposure, rather than assigning every component an unrelated failure time.<ref name="IFEG_1.6-4">Australian Building Codes Board et al. (2005), p. 1.6-4.</ref><ref name="IFEG_1.6-8">Australian Building Codes Board et al. (2005), p. 1.6-8.</ref>


Firefighters may also rely on compartment boundaries for access and intervention. C/VM2 has a dedicated firefighting scenario, while its general fire-safety-system definition includes restricting fire spread and limiting structural instability. The required performance should be identified before assigning a rating or modelling a boundary.<ref name="CVM2-49" /><ref name="CVM2-64" />
== Doors, ducts and service penetrations ==


Compartmentation can change during the incident as occupants escape and firefighters enter. Those door states change smoke and oxygen transport, so an ASET calculation should use the actual sequence rather than assuming all barriers remain closed. This makes compartmentation part of the evacuation scenario, not only a construction detail.<ref name="CVM2-14" />
A [[Fire door]] protects an opening that must also permit normal access and evacuation, and its closed-state performance is part of the compartment boundary. Its open state creates a different route for heat and smoke. The International Fire Engineering Guidelines consequently connect door-opening times to the analysis of occupant movement.<ref name="CVM_64" /><ref name="IFEG_1.6-7" />


== Design and regulation ==
A [[Fire damper]] addresses the internal path through a ventilation opening or duct. Iqbal and Salley describe devices that close in response to a fusible link or remote signal. Their account distinguishes the fire-resistance function from the conditions under which the damper can close against airflow. Those conditions depend partly on whether ventilation is stopped.<ref name="N_F-19">Iqbal and Salley (2004), p. F-19.</ref>


C/VM2 defines firecells and fire separations within New Zealand's 2025 second edition. It also requires construction detailing to match the design and proprietary fire stops to suit their orientation and separating element. Those requirements are jurisdiction-specific and should not be replaced with a generic wall label.<ref name="CVM2-13" /><ref name="CVM2-64" />
[[Firestopping]] addresses gaps and penetrations that would otherwise weaken the separation. Around a duct, it protects the path between the duct assembly and the surrounding boundary. Closing the air passage inside the duct is a different function. A design can therefore need both a closure and a suitable seal at the same crossing.<ref name="N_F-19" /><ref name="N_F-44">Iqbal and Salley (2004), p. F-44.</ref>


The rating alone does not describe the whole fire scenario. Compartment geometry, fuel inventory, openings, active systems and occupants determine whether the boundary provides the intended benefit. Performance-based analysis must show those interactions rather than simply declaring the compartment fire rated.<ref name="IFEG-1.6-3" /><ref name="IFEG-1.6-7" />
New Zealand's 2025 C/VM2 construction provisions connect these details to the completed design, and its commentary calls for proprietary firestopping suited to the orientation and the separating element. It also identifies testing of rated closures under an internationally recognised standard. These provisions concern the installed construction, not a material name or an isolated product label.<ref name="CVM_13">Ministry of Business, Innovation and Employment (2025), p. 13.</ref>


Historic standards provide useful construction evidence but should not be turned into universal values. NUREG-1805 gives typical fire resistance for brick and concrete-block walls and separate expectations for fire walls and fire barriers. Those examples come from a US nuclear reference and do not replace project-specific testing or current local requirements.<ref name="NUREG-1805-17-7" />
== Smoke separation and pressure differences ==


The World Trade Center investigation illustrates a different regulatory pathway. Local rules allowed floor-area compartmentation or sprinklers, and passive protection was chosen to achieve required ratings. It shows that compartmentation is one option within a wider fire-safety strategy, not the only possible form of compliance.<ref name="NIST-1-6A-13">National Institute of Standards and Technology (2005), p. 13.</ref>
Restricting fire spread and restricting smoke movement are related but distinct functions. Smoke can pass through cracks and leakage paths while a boundary remains intact. Klote identifies gaps around doors, pipe penetrations and wall-to-floor junctions as examples. The pressure difference across the boundary determines the driving force for that leakage.<ref name="Kl_4-277_4-278">Klote (2002), pp. 4-277–4-278.</ref>


== Reliability and maintenance ==
Several forces can create the pressure difference. Klote discusses buoyancy from heating, stack effect, wind and mechanical ventilation, and these can act together, so smoke movement is not determined by temperature alone. Stopping ventilation fans removes one influence but does not eliminate movement driven by the others.<ref name="Kl_4-274">Klote (2002), p. 4-274.</ref><ref name="Kl_4-277">Klote (2002), p. 4-277.</ref>


Compartmentation depends on construction matching the design. Doors can be wedged open, seals can be damaged, coatings can be missing and penetrations can be altered during refurbishment. Those changes can invalidate an otherwise sound original design.<ref name="CVM2-13" /><ref name="NIST-1-6A-iii">National Institute of Standards and Technology (2005), p. iii.</ref>
Mechanical smoke control can use pressure differences across closed boundaries and airflow through open doorways. The appropriate assessment changes when a door opens. A pressure difference across a mostly closed barrier is not equivalent to the airflow required through a large opening. Klote therefore distinguishes closed-door and open-door conditions.<ref name="Kl_4-278_4-279">Klote (2002), pp. 4-278–4-279.</ref>


The WTC passive-protection review specifically evaluates insulation thickness, gaps and adhesive or cohesive strengths. These details affect whether the protection remains in place and performs as intended. Compartment boundaries should therefore be inspected as physical systems rather than only as drawings.<ref name="NIST-1-6A-iii" />
C/VM2, second edition of 2025, likewise distinguishes fire separations, smoke separations and unrated construction within the trial design. The method applies different assumptions to their continued presence during a fire. Those assumptions describe the analysis framework and the evidence attributed to each separation. They are not predictions that every physical partition disappears at one identical temperature.<ref name="CVM_14_15">Ministry of Business, Innovation and Employment (2025), pp. 14–15.</ref>


Test evidence should match the assembly and its orientation. A product tested in one wall, floor or penetration arrangement may behave differently in another. C/VM2 explicitly calls for appropriate proprietary products for orientation and use, and fire-resistance ratings require relevant standard-test evidence or verified calculation.<ref name="CVM2-13" /><ref name="CVM2-64" />
== Representing openings in an analysis ==


Maintenance must preserve operation as well as material condition. Fire doors must close and latch, dampers must activate, and seals must remain continuous. A compartment that appears intact during inspection can still fail if these functions are not maintained.<ref name="CVM2-14" /><ref name="NUREG-1805-F-19" />
The International Fire Engineering Guidelines begin with the enclosure geometry, openings and properties of barriers and structural elements. They also require the location and ignition characteristics of material in adjacent spaces, and this information establishes what can be exposed if a route opens. A boundary failure and the ignition of another fuel item are separate events unless the method deliberately combines them.<ref name="IFEG_1.6-5_1.6-7" />


== Limits and common misunderstandings ==
The guidelines permit simplifying assumptions for specified analyses. Examples include treating barrier failure as spread or using flashover as an opening-related event. They also identify conditions that can invalidate a simplification, such as direct flame contact on an unrated boundary. An assumption is therefore part of the model definition, rather than an observed fact about every fire.<ref name="IFEG_1.6-6" />


Compartmentation is not a single fire-rated wall. It is the complete arrangement of enclosing elements, openings, penetrations and junctions. Any weak or altered detail can become the pathway that determines spread.<ref name="CVM2-13" /><ref name="IFEG-1.6-7" />
Door use provides a practical example. Under New Zealand's 2025 C/VM2, a self-closing fire or smoke-control door is assumed closed except when occupants use it. With low occupant demand, it is modelled open for three seconds per occupant. Where occupants queue, the method instead considers the sustained opening associated with that queue.<ref name="CVM_15">Ministry of Business, Innovation and Employment (2025), p. 15.</ref>


A fire rating does not guarantee zero fire or smoke spread. Conduction, radiation, debris, open doors and failed components can still expose adjacent spaces. The analysis must state which pathways and criteria are included.<ref name="IFEG-1.6-7" /><ref name="VR-5.1" />
The same document uses half the door width for smoke-flow modelling while the door is being used for egress. Its commentary explains that a moving leaf and passing occupants restrict the unobstructed opening, and this is a smoke-modelling assumption within C/VM2. It is not a rule that halves the physical escape width of every doorway.<ref name="CVM_15_16">Ministry of Business, Innovation and Employment (2025), pp. 15–16.</ref>


Noncombustible construction is not automatically fire resistant. Materials can deform, crack, lose stability or transmit heat, and those failures can compromise the compartment. Material choice and assembly performance are different questions.<ref name="Kodur-Harmathy-1-155">Kodur and Harmathy (2002), p. 1-155.</ref>
The concealed-space scenario in New Zealand's 2025 C/VM2 provides a specific example of protecting a route that is not visible from an occupied room. It applies within the stated scope to buildings containing rooms with more than 50 occupants and concealed spaces. The document identifies separating elements, suppression and detection as approaches to that scenario. Their acceptance depends on the scenario conditions, rather than an unrestricted exchange between systems.<ref name="CVM_41">Ministry of Business, Innovation and Employment (2025), p. 41.</ref>


Finally, compartmentation does not replace evacuation, detection or suppression. It provides time and space for those responses, but their effectiveness depends on the complete scenario and on maintaining the separating system.<ref name="IFEG-1.6-3" /><ref name="NUREG-1805-F-44" />
Where its separating-element approach is used without automatic detection, C/VM2 specifies at least 30 minutes for integrity and insulation and limits the concealed-space area to 500 m². These figures belong to the particular 2025 New Zealand scenario; they do not define a universal compartment size or barrier rating. The example shows how the route, detection assumptions and separating construction are connected within a stated method.<ref name="CVM_41" />


A system review should map every boundary and every opening, including those that are normally concealed. Each path should be assigned a closure, a firestop or an explicit assumption, so that no route is left without analysis. This is more reliable than reviewing only the largest walls.<ref name="CVM2-13" /><ref name="IFEG-1.6-7" />
== Integration with the fire safety strategy ==


The receiving compartments should be included in that map. Their fuel, occupants and active systems determine what happens if heat or smoke crosses, and their own separations affect later spread. A barrier can therefore be evaluated properly only as part of a sequence of connected firecells.<ref name="IFEG-1.6-3" /><ref name="Kanury-2-231">Kanury (2002), pp. 2-231–2-232.</ref>
Compartmentation forms part of [[Passive fire protection]], but it interacts with systems that operate during an incident. A door may need to close, and a ventilation closure may depend on a signal or the state of a fan. The International Fire Engineering Guidelines distinguish static barriers from operable closures. Describing the whole strategy as having no operational dependencies would conceal those differences.<ref name="IFEG_1.6-9">Australian Building Codes Board et al. (2005), p. 1.6-9.</ref><ref name="N_F-19" />


Junctions deserve particular attention because they join different assemblies and exposure conditions. Roof decks, exterior walls, shaft walls and floor intersections can all change the heat and structural path. A rating for one straight wall segment does not establish those junction details.<ref name="NUREG-1805-17-7" /><ref name="Rockett-Milke-1-29" />
The expected duration of separation follows its purpose in the strategy. The guidelines connect times of spread and structural failure to evacuation, firefighting and protection of adjoining property. Different objectives can therefore require different outputs from the same physical analysis. A nominal duration without an endpoint or objective does not define the required performance.<ref name="IFEG_1.6-2">Australian Building Codes Board et al. (2005), p. 1.6-2.</ref><ref name="IFEG_1.6-4" />


For evacuation, the boundary should be evaluated at the times when people actually pass. Door opening, queuing and fire service access can change both smoke transport and the available escape time. The model should preserve that sequence instead of treating the compartment as sealed throughout.<ref name="CVM2-14" /><ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref>
Compartmentation can also be evaluated alongside suppression. Iqbal and Salley's distinction between fire walls and barriers specifically refers to whether other protective measures are credited. The consequences of losing that support differ from the behaviour assumed when it operates. The design basis therefore identifies which systems and operating conditions form part of the assessment.<ref name="N_17-7">Iqbal and Salley (2004), p. 17-7.</ref>


For structural assessment, boundary failure can be both a cause and a result of fire damage. Heat can weaken a wall or its supports, and collapse can create an opening that changes ventilation. This links compartment performance with the structural analysis rather than treating them as separate reports.<ref name="IFEG-1.6-7" /><ref name="Fleischmann-Buchanan-4-242">Fleischmann and Buchanan (2002), p. 4-242.</ref>
Structural support is another dependency within the strategy. A protected boundary may rely on columns, beams or floors to remain in place. The guidelines require consideration of failure of those supporting elements and its effects on other boundaries. Treating each rating independently would omit a physical route by which several protections can be lost together.<ref name="IFEG_1.6-8" />


Evidence should be checked against the actual products and installation. Proprietary closures and firestops need appropriate orientation, while an older rating may rely on details that no longer exist. Inspection and documentation should confirm that the analysed assembly is the one present in the building.<ref name="CVM2-13" /><ref name="NIST-1-6A-iii">National Institute of Standards and Technology (2005), p. iii.</ref>
== Construction, alterations and continued performance ==


A final review should distinguish intended containment from demonstrated performance. The design may intend to restrict fire, but tests, calculations and incident evidence determine how long and under what conditions it works. Reporting those conditions makes compartmentation a verifiable safety measure rather than a generic label.<ref name="CVM2-64" /><ref name="Milke-4-209">Milke (2002), p. 4-209.</ref>
Construction and commissioning establish whether the intended boundaries exist and their components match the specification. The International Fire Engineering Guidelines identify barrier integrity, specified materials and operation of automatic closures as distinct checks. They also include operation and maintenance documents. The completed system therefore includes both physical construction and information about its required functions.<ref name="IFEG_1.6-9" />


A final check is whether the compartment's actual fire scenario supports the intended separation. Fuel, openings and occupants can change which boundary is needed and when it must perform. The assessment should use those conditions rather than assigning the same rating to every compartment.<ref name="IFEG-1.6-3" /><ref name="CVM2-64" />
Later repairs or alterations can change that system. The guidelines note that passive barriers are liable to be overlooked during building modifications. Their continued identification helps connect a new service opening or construction change to the original fire strategy. Without that connection, a local alteration can change a boundary whose role is not visible from the room alone.<ref name="IFEG_1.6-9" />


The report should also identify which criteria have and have not been verified. Structural adequacy, integrity and insulation require appropriate evidence, while smoke movement and escape require a scenario analysis. Keeping those outputs separate prevents a general fire rating from being mistaken for a complete safety result.<ref name="CVM2-64" /><ref name="CVM2-14" />
Static barriers and operable closures have different maintenance needs. The guidelines describe relatively limited routine maintenance for passive barriers, while calling for operational testing of automatic closures. Inspection and records preserve evidence about both. A wall remaining in place and a door closing correctly are separate observations within the same compartmentation system.<ref name="IFEG_1.6-9" />


For final acceptance, the complete sequence of boundaries, openings and active systems should be reviewed together. A compartment is only protected when the intended separation, its closures and the scenario assumptions agree. This prevents a rating on one component from being treated as proof of building-wide containment.<ref name="CVM2-64" /><ref name="IFEG-1.6-7" />
Evidence of performance remains tied to the construction and conditions assessed. A standard test demonstrates specified functions of its assembly, while modelling represents selected exposures, openings and dependencies; their combined interpretation identifies where the boundary is expected to remain effective. It also identifies the assumptions that cease to hold when the building or its operating conditions change.<ref name="M_4-209_4-210">Milke (2002), pp. 4-209–4-210.</ref><ref name="IFEG_1.6-5_1.6-9">Australian Building Codes Board et al. (2005), pp. 1.6-5–1.6-9.</ref>


== See also ==
== See also ==


* [[Cavity barrier]]
* [[Cavity barrier]]
* [[Fire resistance criteria]]
* [[Protected escape route]]
* [[Fire safety strategy]]
* [[Stay-put strategy]]
* [[Progressive horizontal evacuation]]


== Notes ==
== Notes ==
Line 122: Line 108:
== References ==
== References ==


* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines''. Australian Building Codes Board.
* Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Iqbal, N., & Salley, M. H. (2004). ''Fire dynamics tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission fire protection inspection program'' (NUREG-1805). U.S. Nuclear Regulatory Commission.
* Ministry of Business, Innovation and Employment. (2025). ''C protection from fire: Verification method C/VM2'' (2nd ed.). New Zealand Government.
* Klote, J. H. (2002). Smoke control. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-274–4-291). National Fire Protection Association.
* National Institute of Standards and Technology. (2005). ''Passive fire protection'' (NIST NCSTAR 1-6A). U.S. Department of Commerce.
* Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 1-155–1-181). National Fire Protection Association.
* Rockett, J. A., & Milke, J. A. (2002). Conduction of heat in solids. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Milke, J. A. (2002). Analytical methods for determining fire resistance of steel members. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-209–4-238). National Fire Protection Association.
* U.S. Nuclear Regulatory Commission. (2005). ''Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program'' (NUREG-1805). Author.
* Ministry of Business, Innovation and Employment. (2025). ''C protection from fire: Verification method C/VM2'' (2nd ed.).
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* White, R. H. (2002). Analytical methods for determining fire resistance of timber members. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.


[[Category:Passive Fire Protection]]
[[Category:Passive Fire Protection]]

Latest revision as of 19:41, 2 November 2026

Fire compartmentation is the division of a building into spaces separated by construction intended to restrict the spread of fire and its effects. Walls, floors, closures and protected penetrations work together as a boundary. Its performance depends on maintaining the required structural, integrity and heat-transmission functions under the relevant exposure.[1][2][3]

The separation is not defined by a wall alone. Doors, ventilation openings, service penetrations, junctions and supporting construction can determine how a fire reaches another space. Some routes exist from the outset, while others develop through opening, damage or structural failure. Concealed voids and shafts can connect spaces beyond the room of origin.[4]

Smoke movement adds a further consideration because intact construction can still contain leakage paths. Pressure differences drive flow through those paths and through open doors. Compartmentation consequently interacts with evacuation, ventilation and smoke control, as well as the fire resistance of its materials and assemblies.[5][6]

The compartment boundary

A compartment is a volume separated from other spaces by construction intended to restrict fire effects, and its boundary can include walls, floors, a roof and closures within those elements. New Zealand's C/VM2, second edition of 2025, calls the enclosed volume a firecell. Its definition allows contiguous spaces on the same or different levels, rather than limiting a firecell to one room.[3]

The boundary is therefore a complete system of construction and protected openings. The definition of a fire barrier in NUREG-1805 includes supports, penetration seals, closures, doors and dampers alongside walls and floors. That report was prepared for the United States nuclear regulatory inspection programme. Its terminology usefully identifies the interacting components without establishing requirements for every other building type.[2]

Firecell bounded by walls, floor, roof, fire door, damper and penetration seals.
A firecell is a complete separating system. Based on Ministry of Business, Innovation and Employment (2025), p. 64.

Fire resistance describes how the construction maintains specified functions under an exposure. Those functions include structural adequacy, integrity and insulation where applicable: the first concerns load-bearing performance, the second passage of flames or hot gases, and the third heat transmission. A compartment boundary can lose one function while retaining another.[1][7][3]

A Fire wall is one form of separating construction, but its precise role depends on the governing framework. Iqbal and Salley distinguish a wall intended to remain stable through an uncontrolled fire from a barrier used with other protective measures. That distinction belongs to their discussion of United States practice. It does not make every internal partition a structurally independent fire wall.[8]

Routes by which fire can spread

Fire spread between compartments can follow openings that already exist or openings created during the fire, and the 2005 International Fire Engineering Guidelines treat both categories explicitly. Doors and windows may be open initially, while glazing breakage or damage can create further routes. The state of each route can change as the event develops.[9][10]

An opening can also result from missing or inadequate sealing around services. Pipes, cable trays and ventilation ducts cross boundaries to perform normal building functions. Those crossings need their own representation in the separating system. A sound wall surface does not describe the behaviour of an unprotected opening through it.[10][11]

Concealed spaces can connect locations that appear separate in an occupied room, and the guidelines identify ceiling voids, hollow construction, spaces under floors and spaces behind external cladding. Shafts and large service ducts can provide vertical routes. In the analysis, these spaces become further enclosures with their own connections and boundaries.[10]

The route can also pass outside the building before re-entering another space, and the guidelines discuss flames projecting from windows, radiation and burning debris. Adjacent buildings can be exposed through openings or external surfaces. Compartmentation therefore cannot be assessed solely by tracing internal partition lines on a floor plan.[12]

Fire and smoke passing through a door, duct, cable penetration, cavity and wall end.
Openings and junctions can bypass a fire-rated wall. Based on Australian Building Codes Board et al. (2005), p. 1.6-7 and Iqbal and Salley (2004), p. 17-8.

Thermal, integrity and stability failures

Heat can pass through an intact boundary by conduction. The unexposed surface may then become hot enough to breach an insulation criterion or ignite nearby material under suitable conditions. This mechanism does not require a visible hole. The thermal properties, thickness and exposure history influence the resulting temperature distribution.[6][13]

Loss of integrity introduces a path through the boundary. Cracks, fissures and failed penetration protection can permit hot gases or flames to pass. Whether adjacent material ignites depends on its location and response to the exposure. The International Fire Engineering Guidelines distinguish this physical sequence from a simplified analysis that equates barrier failure with spread.[14]

Loss of stability means that the barrier or its supporting construction can no longer remain in place, so a wall can fail because another structural element supporting it fails. The guidelines identify this dependency explicitly. The endurance of an isolated wall specimen is therefore not sufficient evidence for a boundary whose support fails earlier.[15]

Three panels: heat through an intact wall, cracks with smoke and a collapsed wall.
Compartment boundaries can fail thermally, through integrity or through stability. Based on Australian Building Codes Board et al. (2005), p. 1.6-7.

These mechanisms can interact during the same fire. An opening can change ventilation as well as permit spread into another enclosure. Structural loss can damage several boundaries together. The analysis therefore follows changes in the building and exposure, rather than assigning every component an unrelated failure time.[16][17]

Doors, ducts and service penetrations

A Fire door protects an opening that must also permit normal access and evacuation, and its closed-state performance is part of the compartment boundary. Its open state creates a different route for heat and smoke. The International Fire Engineering Guidelines consequently connect door-opening times to the analysis of occupant movement.[3][6]

A Fire damper addresses the internal path through a ventilation opening or duct. Iqbal and Salley describe devices that close in response to a fusible link or remote signal. Their account distinguishes the fire-resistance function from the conditions under which the damper can close against airflow. Those conditions depend partly on whether ventilation is stopped.[18]

Firestopping addresses gaps and penetrations that would otherwise weaken the separation. Around a duct, it protects the path between the duct assembly and the surrounding boundary. Closing the air passage inside the duct is a different function. A design can therefore need both a closure and a suitable seal at the same crossing.[18][19]

New Zealand's 2025 C/VM2 construction provisions connect these details to the completed design, and its commentary calls for proprietary firestopping suited to the orientation and the separating element. It also identifies testing of rated closures under an internationally recognised standard. These provisions concern the installed construction, not a material name or an isolated product label.[20]

Smoke separation and pressure differences

Restricting fire spread and restricting smoke movement are related but distinct functions. Smoke can pass through cracks and leakage paths while a boundary remains intact. Klote identifies gaps around doors, pipe penetrations and wall-to-floor junctions as examples. The pressure difference across the boundary determines the driving force for that leakage.[21]

Several forces can create the pressure difference. Klote discusses buoyancy from heating, stack effect, wind and mechanical ventilation, and these can act together, so smoke movement is not determined by temperature alone. Stopping ventilation fans removes one influence but does not eliminate movement driven by the others.[22][23]

Mechanical smoke control can use pressure differences across closed boundaries and airflow through open doorways. The appropriate assessment changes when a door opens. A pressure difference across a mostly closed barrier is not equivalent to the airflow required through a large opening. Klote therefore distinguishes closed-door and open-door conditions.[24]

C/VM2, second edition of 2025, likewise distinguishes fire separations, smoke separations and unrated construction within the trial design. The method applies different assumptions to their continued presence during a fire. Those assumptions describe the analysis framework and the evidence attributed to each separation. They are not predictions that every physical partition disappears at one identical temperature.[25]

Representing openings in an analysis

The International Fire Engineering Guidelines begin with the enclosure geometry, openings and properties of barriers and structural elements. They also require the location and ignition characteristics of material in adjacent spaces, and this information establishes what can be exposed if a route opens. A boundary failure and the ignition of another fuel item are separate events unless the method deliberately combines them.[12]

The guidelines permit simplifying assumptions for specified analyses. Examples include treating barrier failure as spread or using flashover as an opening-related event. They also identify conditions that can invalidate a simplification, such as direct flame contact on an unrated boundary. An assumption is therefore part of the model definition, rather than an observed fact about every fire.[10]

Door use provides a practical example. Under New Zealand's 2025 C/VM2, a self-closing fire or smoke-control door is assumed closed except when occupants use it. With low occupant demand, it is modelled open for three seconds per occupant. Where occupants queue, the method instead considers the sustained opening associated with that queue.[26]

The same document uses half the door width for smoke-flow modelling while the door is being used for egress. Its commentary explains that a moving leaf and passing occupants restrict the unobstructed opening, and this is a smoke-modelling assumption within C/VM2. It is not a rule that halves the physical escape width of every doorway.[27]

The concealed-space scenario in New Zealand's 2025 C/VM2 provides a specific example of protecting a route that is not visible from an occupied room. It applies within the stated scope to buildings containing rooms with more than 50 occupants and concealed spaces. The document identifies separating elements, suppression and detection as approaches to that scenario. Their acceptance depends on the scenario conditions, rather than an unrestricted exchange between systems.[28]

Where its separating-element approach is used without automatic detection, C/VM2 specifies at least 30 minutes for integrity and insulation and limits the concealed-space area to 500 m². These figures belong to the particular 2025 New Zealand scenario; they do not define a universal compartment size or barrier rating. The example shows how the route, detection assumptions and separating construction are connected within a stated method.[28]

Integration with the fire safety strategy

Compartmentation forms part of Passive fire protection, but it interacts with systems that operate during an incident. A door may need to close, and a ventilation closure may depend on a signal or the state of a fan. The International Fire Engineering Guidelines distinguish static barriers from operable closures. Describing the whole strategy as having no operational dependencies would conceal those differences.[29][18]

The expected duration of separation follows its purpose in the strategy. The guidelines connect times of spread and structural failure to evacuation, firefighting and protection of adjoining property. Different objectives can therefore require different outputs from the same physical analysis. A nominal duration without an endpoint or objective does not define the required performance.[30][16]

Compartmentation can also be evaluated alongside suppression. Iqbal and Salley's distinction between fire walls and barriers specifically refers to whether other protective measures are credited. The consequences of losing that support differ from the behaviour assumed when it operates. The design basis therefore identifies which systems and operating conditions form part of the assessment.[31]

Structural support is another dependency within the strategy. A protected boundary may rely on columns, beams or floors to remain in place. The guidelines require consideration of failure of those supporting elements and its effects on other boundaries. Treating each rating independently would omit a physical route by which several protections can be lost together.[17]

Construction, alterations and continued performance

Construction and commissioning establish whether the intended boundaries exist and their components match the specification. The International Fire Engineering Guidelines identify barrier integrity, specified materials and operation of automatic closures as distinct checks. They also include operation and maintenance documents. The completed system therefore includes both physical construction and information about its required functions.[29]

Later repairs or alterations can change that system. The guidelines note that passive barriers are liable to be overlooked during building modifications. Their continued identification helps connect a new service opening or construction change to the original fire strategy. Without that connection, a local alteration can change a boundary whose role is not visible from the room alone.[29]

Static barriers and operable closures have different maintenance needs. The guidelines describe relatively limited routine maintenance for passive barriers, while calling for operational testing of automatic closures. Inspection and records preserve evidence about both. A wall remaining in place and a door closing correctly are separate observations within the same compartmentation system.[29]

Evidence of performance remains tied to the construction and conditions assessed. A standard test demonstrates specified functions of its assembly, while modelling represents selected exposures, openings and dependencies; their combined interpretation identifies where the boundary is expected to remain effective. It also identifies the assumptions that cease to hold when the building or its operating conditions change.[32][33]

See also

Notes

  1. ↑ 1.0 1.1 Kodur and Harmathy (2002), p. 1-155.
  2. ↑ 2.0 2.1 Iqbal and Salley (2004), p. F-24.
  3. ↑ 3.0 3.1 3.2 3.3 Ministry of Business, Innovation and Employment (2025), p. 64.
  4. ↑ Australian Building Codes Board et al. (2005), pp. 1.6-6–1.6-8.
  5. ↑ Klote (2002), pp. 4-277–4-279.
  6. ↑ 6.0 6.1 6.2 Australian Building Codes Board et al. (2005), p. 1.6-7.
  7. ↑ Milke (2002), pp. 4-210–4-211.
  8. ↑ Iqbal and Salley (2004), pp. 17-7–17-8.
  9. ↑ Australian Building Codes Board et al. (2005), p. 1.6-1.
  10. ↑ 10.0 10.1 10.2 10.3 Australian Building Codes Board et al. (2005), p. 1.6-6.
  11. ↑ Iqbal and Salley (2004), p. 17-8.
  12. ↑ 12.0 12.1 Australian Building Codes Board et al. (2005), pp. 1.6-5–1.6-7.
  13. ↑ Van Rossum (2027), §5.2.
  14. ↑ Australian Building Codes Board et al. (2005), pp. 1.6-6–1.6-7.
  15. ↑ Australian Building Codes Board et al. (2005), pp. 1.6-7–1.6-8.
  16. ↑ 16.0 16.1 Australian Building Codes Board et al. (2005), p. 1.6-4.
  17. ↑ 17.0 17.1 Australian Building Codes Board et al. (2005), p. 1.6-8.
  18. ↑ 18.0 18.1 18.2 Iqbal and Salley (2004), p. F-19.
  19. ↑ Iqbal and Salley (2004), p. F-44.
  20. ↑ Ministry of Business, Innovation and Employment (2025), p. 13.
  21. ↑ Klote (2002), pp. 4-277–4-278.
  22. ↑ Klote (2002), p. 4-274.
  23. ↑ Klote (2002), p. 4-277.
  24. ↑ Klote (2002), pp. 4-278–4-279.
  25. ↑ Ministry of Business, Innovation and Employment (2025), pp. 14–15.
  26. ↑ Ministry of Business, Innovation and Employment (2025), p. 15.
  27. ↑ Ministry of Business, Innovation and Employment (2025), pp. 15–16.
  28. ↑ 28.0 28.1 Ministry of Business, Innovation and Employment (2025), p. 41.
  29. ↑ 29.0 29.1 29.2 29.3 Australian Building Codes Board et al. (2005), p. 1.6-9.
  30. ↑ Australian Building Codes Board et al. (2005), p. 1.6-2.
  31. ↑ Iqbal and Salley (2004), p. 17-7.
  32. ↑ Milke (2002), pp. 4-209–4-210.
  33. ↑ Australian Building Codes Board et al. (2005), pp. 1.6-5–1.6-9.

References

  • Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). International fire engineering guidelines. Australian Building Codes Board.
  • Iqbal, N., & Salley, M. H. (2004). Fire dynamics tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission fire protection inspection program (NUREG-1805). U.S. Nuclear Regulatory Commission.
  • Klote, J. H. (2002). Smoke control. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed., pp. 4-274–4-291). National Fire Protection Association.
  • Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed., pp. 1-155–1-181). National Fire Protection Association.
  • Milke, J. A. (2002). Analytical methods for determining fire resistance of steel members. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed., pp. 4-209–4-238). National Fire Protection Association.
  • Ministry of Business, Innovation and Employment. (2025). C protection from fire: Verification method C/VM2 (2nd ed.).
  • Van Rossum, E. (2027). Introduction to Fire Safety Engineering. Fire Safety Academy.
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