Understanding compartmentation as a passive fire safety technique

NFPA 101 insights

• Compartmentation, including fire barriers and smoke barriers, is vital for limiting fire and smoke spread, to ensure the safety of building occupants.
• Active systems detect and respond to fires, while passive systems are integral to the building’s construction and aim to control the spread of fire and smoke. Understanding how both types of systems work together is essential for effective fire protection

At the time of its initial publication in 1927, NFPA 101: Life Safety Code was titled the Building Exits Code and was primarily focused on methods to safely affect exit burning structures. In the following decades, NFPA 101 became the Life Safety Code, and grew to contain over 40 chapters. While the effective means of egress covered in NFPA 101, Chapter 7 cannot be taken for granted, a lack of familiarity with further topics in the code causes confusion and lack of clarity.

NFPA 101 dictates the collection of fire protection features that are intended to work together to protect people in the event of an emergency. These systems include fire suppression systems, fire alarm systems, egress systems and building compartmentation. Many architects and engineers struggle to understand the differences between fire and smoke barriers and when each are required. People frequently call fire resistance-rated construction a “firewall,” not realizing that what they mean is “fire barrier” and that a firewall is an entirely different construction element.

Passive and active fire protection

There are two types of fire protection: active and passive. Compartmentation falls under the category of passive fire protection, which is integral to the building’s construction and aims to control a fire and limit the spread of its effects to other areas of the structure by using fire and smoke resistant materials in specific walls, ceilings and floors.

Compartmentation is defined in NFPA 101, Chapter 8, Features of Fire Protection as the practice of separating a structure into “compartments” to reduce the spread of fire and smoke. Fire and smoke make up the two main categories for classifying compartments, as defined in NFPA 101, Chapter 3, Section 3.3.49. Within the sections for either fire or smoke, NFPA 101 specifies and references the classifications and constructions of the architectural and structural elements designed to resist the spread of fire and limit its detrimental effects.

Active systems, on the other hand, trigger a response or are applied under conditions that indicate the presence of fire or its byproducts. This kind of system is represented by what is often associated with fire protection overall; i.e., smoke detectors, sprinkler systems and fire extinguishers. Active systems are likely the ones to detect or extinguish a fire, while passive systems are the ones to reduce or limit how much of the structure a fire reaches or damages. These features help limit occupant exposure to the effects of a fire and are intended to help protect egress paths.

Figure 1: A fire barrier wall in new construction before installation of fire-stopping materials at the through penetrations. Courtesy: CDM Smith

Including both active and passive fire protection in a structure’s design helps limit the impact of a fire, and while active systems are often more obvious, best results come from understanding the uses and expected results of passive fire protection. Containing the fire allows more time for egress and fire department activities. By slowing down a fire, even temporarily, passive systems can save lives and lessen property damage.

Compartmentation with fire barriers

Fire barriers are defined in NFPA 101, Chapter 3, Section 3.3.32.1 as a continuous membrane or a membrane with discontinuities, created by a protected opening with a specified fire protection rating, where such membrane is designed and constructed to limit the spread of fire. Doors in fire barriers must be rated in accordance with the opening protective requirements of NFPA 101, Section 8.4.3, and must be self-closing with positive latching.

Where penetrations are required in fire barriers, they must be sealed with fire-stop using an approved, assembly-tested and installed in accordance with the manufacturer’s instructions. There is often confusion about whether recessed fixtures or equipment may be installed in a fire barrier. NFPA 101, Section 8.3.4.7 allows certain articles to be recessed into fire barriers if they only penetrate one membrane of the rated wall and meet specific limitations on size and type of penetration.

Where fire barrier systems join exterior walls, other fire barriers, floor, ceiling or roof assemblies, joints are required to be constructed using a tested joint system assembly that is appropriate for the construction type and meets the minimum fire resistance rating requirements.

Smoke barriers and smoke partitions for compartmentation

Smoke barriers, per NFPA 101, Chapter 3, Section 3.3.32.2, are a continuous membrane or a membrane with discontinuities, created by protected openings, where such membrane is designed and constructed to restrict the movement of smoke. The definition of smoke partition in NFPA 101, sounds like that of a smoke barrier, which often leads to confusion. However, there are a few key differences.

Smoke barriers are constructed as a continuous membrane, like fire barriers, but have the additional requirement of limiting air transfer. This generally necessitates the inclusion of smoke detection and automatically closing smoke dampers at duct penetrations and air transfer openings. Because smoke barriers oftentimes are also required to carry a fire resistance rating, they are commonly thought of as fire barriers with additional protections to prevent smoke movement.

Figure 2: A penetration in a rated fire barrier that has not been provided with the required opening protective. Courtesy: CDM Smith

Smoke partitions, on the other hand, require means to prevent air transfer across the barrier, but may omit smoke dampers in the case of duct penetrations. They may have doors that are self-closing but not positive latching.

Typically, NFPA 101 requires the subdivision of certain occupancies into smoke compartments with smoke barriers. These smoke barriers often require a minimum fire resistance rating of 30 minutes or one hour. Smoke partitions are required most at corridor walls or ceilings when a fire resistance rating of the corridor is not required due to the presence of sprinkler protection.

Like fire barrier walls, where smoke barriers and partitions create joints with wall and floor, or ceiling and roof assemblies, the joint system must be capable of resisting the passage of smoke. Where a smoke barrier is also required to have a fire resistance rating, the joint system must meet the requirements for fire barriers.

Horizontal assemblies

Smoke- and fire-resistant assemblies are not only limited to vertical applications, like walls. Horizontal assemblies, such as floor or ceiling assemblies, are required at building openings in the conversely vertical direction to limit the spread of smoke and fire. As such, horizontal fire barrier and smoke barrier assemblies are used between floor levels to limit the vertical spread of fire and smoke.

Openings through the floor assemblies that serve as these fire and smoke partitions are required to be enclosed with fire barrier walls or smoke partitions that are continuous from floor to floor or floor to roof, and openings are required to be protected. Exceptions allowed to this requirement are listed in NFPA 101, Section 8.6.3. These exceptions include penetrations for building utilities, conveyors, escalators, moving walks and at expansion or seismic joints.

Special hazards

In non sprinklered facilities, areas of the building that have a higher degree of hazard than what is normal to the general occupancy of the building are must be provided with fire barriers, in accordance with NFPA 101, Section 8.7. Where sprinkler protection is provided, these required separations for special hazards can be reduced to smoke partitions unless one of the exceptions listed in Section 8.7.1.2 applies.

The terms firewall and fire barrier are often used interchangeably, but they are not the same thing. In fact, firewalls are not addressed or defined in NFPA 101, but instead are covered by building codes and defined in Chapter 3, Section 3.3.15.6 of NFPA 221, Standard for High Challenge Fire Walls, Fire Walls, and Fire Barrier Walls. Firewalls are required to be structurally independent, allowing the building on each side to collapse without the wall coming down. A firewall is oftentimes used to separate structures that are connected to each other, but managed as separate buildings.

A party wall is a type of firewall that is constructed on a property line where two buildings managed by separate owners might be connected. Both firewalls and party walls are prohibited from having penetrations or openings interconnecting the buildings they separate.

Holistic approaches to compartmentation

Fire barriers, smoke barriers and smoke partitions are part of the collection of systems designed to work together with active fire protection features, such as fire sprinkler protection, fire detection, alarms and smoke control. It is important to review the design of fire protection systems in conjunction with a review of passive fire protection systems.

In one case study, a client had a building designed that included a control area, which needed to be separate from the remainder of the building by a smoke barrier. As a result, air transfer openings in the smoke barrier were required to have smoke dampers. The arrangement of these smoke barriers made the installation of duct smoke detection at the openings impractical, so the design team provided area smoke detection in this space to trigger the smoke dampers to close and prevent the passage of smoke across the smoke barrier in the event of a fire.

A fire alarm reviewer later identified that, because of the presence of sprinkler protection, the building was not required to have area smoke detection (based on its specific use and occupancy). However, the reviewer didn’t recognize that the area detection in this location was required to close the smoke dampers at the smoke barrier walls as duct detection was not provided at the air transfer openings. The reviewer directed the removal of area smoke detection from the design drawings as part of the value engineering process.

Figure 3: Opening corridors allows better workflow and natural light, which can improve the overall feel of a space. Here, corridor walls do not require a rating and the solid ceiling maintains the compartment’s required smoke barrier. Courtesy: CDM Smith

The fire protection consultant identified this error and prevented the mistake from being carried out into the construction drawings, illustrating why it’s important to review fire protection features as a collection of systems, including passive compartmentation fire protection systems.

Renovations and rehabilitations

Owners are frequently unaware of the importance of the passive fire protection systems in their buildings, and may direct renovations that undermine facility compartmentation. An example of a common compartmentation pitfall is the removal of a corridor wall to allow direct light from an open office area. There have also been cases of clients directing the removal of a hard ceiling to access equipment for repair or replacement, but then deciding to replace that hard ceiling with a ceiling cloud system that does not form a continuous smoke partition.

It is important for architects, consulting engineers and building owners to ensure that a thorough review is completed of compartmentation requirements before making changes for utility or cosmetic reasons that might otherwise better allow the spread of fire and smoke should a fire start.

Changes in use or occupancy

As buildings go through changes in use and occupancy, compartmentation requirements can also change. However, in existing structures, this can sometimes be overlooked. During changes in use or occupancy, building code analysis should be conducted by a qualified engineer or architect to determine the compartmentation requirements. They should then be reviewed holistically with the entire fire protection plan for the facility, which will ensure compliance with all applicable compartmentation requirements.

This can be especially troublesome in historic or older buildings that may not have been subject to modern compartmentation requirements during their original construction. Often the necessity of modifying the facility to provide compartmentation may be infeasible or impossible in such buildings. Likewise, when only a portion of a building is being modified, compartmentation may not remain continuous, as it would have to extend beyond the renovation area.

Figure 4: Where smoke partitions are required, extending the smoke partition walls to the underside of the deck can allow removal of ceilings to create a more open area with a more industrial aesthetic. Courtesy: CDM Smith

Consider a facility where a second floor is being renovated but occupants must traverse an existing lower level to reach an exit. If the lower level isn’t in the renovation scope, compartmentation may not be continuous to an exit for occupants of the renovation area. In these cases, it is important to work with the authority having jurisdiction and a qualified fire protection consultant to determine the best path forward.

Inspection and maintenance

Where fire barriers, smoke barriers and smoke partitions are required, building owners are responsible for the maintenance of those barriers and partitions in accordance with NFPA 101, Section 4.5.8. While NFPA 101 doesn’t specifically outline an inspection, testing or maintenance schedule for compartmentation elements such as these, it does have requirements for inspection and testing of fire door assemblies.

Additionally, fire rated doors, smoke dampers and other opening protectives are required to be inspected and maintained in accordance with NFPA 80: Standard for Fire Doors and Other Opening Protectives. Smoke door assemblies also require regular inspection and testing in accordance with NFPA 105: Standard for Smoke Door Assemblies and Other Opening Protectives. Where adopted, NFPA 80 and NFPA 105 apply to both new and existing construction.

Over the life of the building, fire and smoke barriers are frequently penetrated to route new equipment, and these barriers and partitions may not be properly fire-stopped where new penetrations are created. Where ceilings make up part of a smoke partition, elements like missing sprinkler escutcheons, ceiling tiles or access holes that have not been properly repaired can be addressed through these required inspections. Without a valid annual inspection schedule and proper documentation of them, building owners may find it difficult to comply with the inspection, testing and maintenance requirements in NFPA 80, and NFPA 105, or the maintenance requirements in NFPA 101.

Why compartmentation is important

Fire compartmentation is an important part of the collection of systems that make up the entire fire protection envelope for a facility. Understanding the requirements for fire barriers, smoke barriers and smoke partitions can help architects, engineers and facility owners ensure that their facilities remain code compliant.

Ensuring that a facility is protected requires a holistic approach that includes the active systems, like fire alarm and sprinkler systems and passive systems, such as compartmentation. These systems must be maintained over the life of the facility and reevaluated when changes to the facility are made, even if the changes might appear only cosmetic, such as removing a ceiling or a wall. A regular inspection program can help owners ensure that these systems integral to fire protection and life safety are maintained.

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