Smoke Barriers vs. Smoke Partitions
The ICC® International Building Code® (IBC) and/or NFPA 101® requires most fully-sprinklered health care facilities to have fire barriers, smoke barriers, and smoke partitions. Fire barriers are provided for enclosure of vertical openings (e.g., shafts, hoistways) and exits (stairways and passageways), occupancy separation, and separation of hazardous areas.
Smoke barriers are provided for smoke compartmentation or subdivision for the purpose of defend-in-place egress of litterborne patients. Smoke partitions are provided for hazardous area separation, where the hazardous area room or space is sprinklered.
Smoke barriers, with the exception of some atrium separation walls, are required to be fire resistance-rated and constructed in the same manner as fire barriers. Essentially, smoke barriers are fire barriers with some added levels of protection to mitigate smoke migration. The later editions of the codes have provided more details for added levels of protection, including leakage rated through-penetration firestop systems (“L” ratings), and smoke- and draft- control fire doors (“S” labeled).
In contrast, smoke partitions are not required to be fire resistance-rated. The intent of these walls is to limit smoke spread from hazardous areas, which are normally unoccupied and relatively small in area, without requiring the fire resistance-rated walls. The limitations for smoke partitions are often related to air transfer openings, which are prohibited, and non-rated doors which are selfclosing or automatic-closing. Unlike fire doors, smoke partition doors are not required to be positive latching. Smoke dampers are not required in duct penetrations of smoke partitions.
It should be recognized that the IBC’s criteria in Chapter 5 for smoke partitions enclosing hazardous areas, also known as incidental uses or incidental accessory occupancies, differ slightly from smoke partition criteria in Chapter 7 which do not apply to hazardous areas. Similarly, the smoke partition criteria in Chapter 8 of the 2006 and 2009 editions of NFPA 101 do not apply to smokeresisting corridor walls in health care occupancies which are governed in Chapter 18. The criteria for each type of wall should be carefully reviewed during design.
NFPA 101®, the Life Safety Code® (LSC) – 2000 Edition and NFPA 90A, Standard for Heating, Ventilating and Air-Conditioning Systems – 1999 Edition allow smoke dampers to be omitted in ducted penetrations of smoke barriers in fully-sprinklered, new health care occupancies.
For existing health care occupancies, the smoke dampers may be omitted if the smoke compartments adjoining the smoke barrier are protected throughout by automatic sprinklers, the sprinkler system is supervised and electrically connected to the fire alarm system, and all of the sprinklers are listed quickresponse or listed residential-type sprinklers, except where allowed for hazardous areas or where the sprinklers were installed prior to the time that quickresponse sprinklers were listed. Note that the 2000 Edition requires the entire building to be protected by automatic sprinklers.
The 2009 Edition revised the governing section to specify that only the adjoining smoke compartments must be sprinklered to reflect the intent of applying the damper exception to partially sprinklered health care facilities. The intent of the LSC is to prohibit unprotected air transfer openings (i.e., without smoke dampers) that are in smoke barriers.
The 2006 and 2009 editions of the ICC® International Building Code® (IBC) require smoke dampers in duct and air transfer openings in smoke barriers. The only exception to the smoke damper requirement applies to steel ducts that are limited to a single smoke compartment, such as express ducts. Note that the IBC is intended to apply only to new construction. However, the Joint Commission (TJC) or other accreditation agency not evaluate the facility for compliance with the IBC.
In many jurisdictions in which the IBC is adopted, the International Existing Building Code® (IEBC) is also adopted for repairs, alterations to, renovations of, and changes of occupancy in existing buildings. The IEBC does not specify a requirement to provide smoke dampers in existing smoke barriers, but requires that new smoke barriers must comply with the IBC.
If the building was built under a code that required the dampers, they would be identified as “not-codecompliant” if they were not previously provided. For example, the ICBO Uniform Building Code® required dampers in smoke barriers, whereas the BOCA National Building Code® did not require dampers for fully ducted systems.
In summary, the IBC’s provisions for most new buildings require smoke dampers where ducts serve more than one smoke compartment.
NFPA 101 and the IBC require all exit stairs to discharge directly to the exterior of the building. Both codes allow a maximum of 50% of the exits and a maximum of 50% of the egress capacity to discharge into areas on the level of discharge, such as a ground floor or grade-level story (e.g., lobby space or grade-level corridor). The codes require that exit stairs which do not discharge directly outside must be located such that the path remains free and unobstructed to the exterior exit and is readily visible and identifiable.
The 50% criteria are typically applied to the exits serving a particular story. The 50% rule is often met for lower stories that have larger footprints and thus more stairs. However, compliance could be more difficult for upper stories where the number of stairs is reduced due to the smaller footprint.
Thus, the means of egress serving each story must be evaluated for compliance with the exit discharge criteria. In large facilities that have undergone or will undergo expansions, existing exit stairs often become “landlocked” by the new construction such that discharging directly to the outside is not possible.
In order to comply with the exit discharge limitations, existing exit stairs could be required to be considered as discharging directly outside. In these cases, the exit stairs are allowed to be extended to the exterior by exit passageways. Exit passageways are essentially horizontal exit stair enclosures. The term exit enclosure is often applied to include both exit stairs and exit passageways.
Exit passageways must be constructed in the same manner as exit stairs with respect to fire resistance-rated walls, floor/ceiling assemblies and fire doors. The walls and floor/ceilings are typically required to have either a 1-hour fire-resistance rating or a 2-hour fireresistance rating depending on the construction type of the building and the number of stories connected by the exit stair served by the exit passageway.
Similarly, door openings must consist of fire door assemblies (door, frame, hardware, and accessories) having a 1-hour fire-protection rating (for 1-hour fire resistance-rated walls) or a 1½-hour fire-protection rating (for 2-hour fire resistance-rated walls). In buildings where exit passageways are located near building service equipment rooms, the enclosure of the exit passageway can be challenging due to limitations on openings into and penetrations of the enclosure.
The codes prohibit elevators and doors from normally unoccupied spaces, such as mechanical equipment rooms or storage rooms, from opening directly into exit passageways. Note: NFPA 101 provides an exception for certain existing interstitial spaces. It is helpful to think of these as continuations of the stairs.
If it cannot open directly to a stair, then it cannot open to an exit passageway. In cases where it is not feasible to isolate the elevator hoistway openings or other doors from existing rooms from opening into an exit passageway, an alternative compliance approach should be discussed with the code official.
Doors used for egress from normally occupied rooms are allowed to open into exit passageways. In fact, NFPA 101 and IBC require such doors to swing in the direction of egress travel into the exit passageway.
The other significant limitation is on penetrations and other openings into exit passageways. NFPA 101 and the IBC allow only the following items to penetration exit passageways:
In many health care facilities, electronic security (e.g., video cameras) must be provided in exit enclosures for protection of the staff, visitors, or patients. The codes do not specifically permit penetration of the exit enclosure for wiring, conduit or cables associated with security systems.
However, code officials often permit limited penetrations of these systems in consideration of current security practices. Reviewing the security system provisions, including door locking arrangements, with the code official is recommended as part of the design process.
In existing buildings where an exit passageway is necessary and must be near building service equipment rooms, which are often located on the ground floor, existing utilities including ducts, piping, and conduit may traverse the proposed location of the exit passageway.
As described above, such utilities are not permitted to penetrate the exit passageway enclosure. Since these utilities could serve areas outside of the scope of work in the building and shutting down the utilities would disrupt operations, relocating the utilities may not be feasible.
One common method to address this issue is to provide a fire resistance-rated ceiling membrane. This assembly would separate the utilities above from the exit passageway enclosure. Some jurisdictions require that the fire resistance-rated assembly be listed based on fire testing by an approved agency such as Underwriters Laboratories (UL).
Very few assemblies are listed for this purpose and are generally considered as horizontal shaft wall assemblies. In most applications, the fire resistancerated ceiling must be supported by the fire barrier walls. Furthermore, the fire barrier walls forming the exit passageway are required to extend to the underside of the fire resistance-rated floor assembly above.
Complications arise with respect to providing fire dampers in the duct penetrations of the fire barrier walls above the fire resistance-rated ceiling and the location of fire damper access doors. Since the above ceiling interstitial space would be considered as a normally unoccupied space, similar to a utility shaft, openings in the fire resistance-rated ceiling would not be permitted for the same reason as openings from mechanical equipment rooms.
Thus, even fire protection-rated access doors in the ceiling assembly are not allowed. Fire damper access doors should be located on the adjoining room side of the exit passageway. The IBC requires that exit passageways that serve pressurized exit stairs must be pressurized in the same manner as the connected stair. Exceptions allow for not pressurizing the exit passageway if openings other than the door separating the stair and passageway (required by the IBC) and the door leading from the passageway to the exterior are not provided.
The pressurization of exit passageways can be complicated by the location of pressurization fans which are often on the roof of the building. The IBC specifies minimum (0.10 inches of water column or 25 Pascals) and maximum (0.35 inches of water column or 87 Pascals) pressure differentials for stair pressurization. Pressurization ductwork from the roof to the exit passageway may be necessary in order to achieve compliance with the pressure design criteria.
In a recent hospital project, an exit passageway was constructed in an existing building to connect a new exit stair in the addition to the exterior. The new exit stair was required to be pressurized. An air transfer opening was provided above the door separating the stair and passageway. The system was designed such that the passageway could be pressurized via the stair.
Although both the stair and passageway would have minimal contents, in the remote event of a serious fire, the air transfer opening would be sealed by a fire damper and thereby provide the separation required by the code.
It should be noted that this design approach does not comply with the 2009 IBC, which prohibits openings other than fire door assembly between the stair and passageway, but was specifically negotiated with the code official based on the existing constraints of the specific building.
Hughes Associates Opens New Office in San DiegoHughes associates Inc. (HAI), a global company leading the Fire Protection Engineering field, is pleased to announce the opening of the San Diego, California area office. The San Diego Area office is located at 8880 Rio San Diego Drive, Suite 800 in San Diego, California, 92108.
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