SECTION 08 3477 – SMOKE AND FIRE PROTECTIVE CURTAIN ASSEMBLIES
Use of Smoke and Fire Protective Curtain Assemblies is relatively new in the U.S., although it is well-tested and has been used for many years in Europe. There are numerous applications for the use of these curtain assemblies and they can save the Owner much in the way of dollars and building space when compared to a mechanical smoke control based system. When used simply as a draft curtain it may not need to be a fire-rated material, but when the curtain is providing fire protection, the fire rating may range from 20 minutes to three hours. Be aware of the code related requirements for the specific application of your building. United Laboratories (UL) has recently developed standard UL 10D – Safety Fire Tests of Fire Protective Curtain Assemblies, as well as the National Fire Protection Association (NFPA) development of standard NFPA 288 - Standard Methods of Fire Tests of Floor Fire Door Assemblies Installed Horizontally in Fire Resistance-Rated Floor Systems that do not require a hose-stream test of the curtain for compliance. For elevator related applications refer to International Code Council (ICC) Acceptance Criteria AC77 - Smoke-Containment Systems Used with Fire-Resistance-Rated Elevator Hoistway Doors and Frames and at the Intersection of Elevator Lobby and Corridor for specific compliance requirements.
A Smoke Curtain application to protect an atrium space may involve various deployable systems. Curtains may be located at the atrium perimeter and be deployed from the ceiling above upper floor railings overlooking the atrium to prevent smoke from getting into these egress areas so people may safely reach the building exits. These curtains may be sheer sheets of fabric for straight curtain runs, or with an accordion style to accommodate angled corners. Curtains may also be deployed vertically around openings in the floor area such as escalators and open stairways. For smaller floor openings the curtain may be deployed horizontally to close off the flow of smoke and fire between floors.
Another popular application for Smoke and Fire Curtains is for use in conjunction with fire rated elevator hoistway door and frame assemblies, and elevator lobbies as an alternative to providing a fully separated enclosed elevator lobby using fire rated swinging or coiling doors. These Smoke and Fire Curtains are mounted in the head of elevator doors and the ceiling of corridor leading to the elevator lobby area. They are out of sight and provide a less expensive means of compliance with building code requirements. The curtain located at the elevator door may be opened with a strap to manually lift the curtain out of the way, or by pressing a button located on elevator door jamb to open the curtain allowing egress from the elevator. The raised curtain will then redeploy if the presence of smoke is still being detected.
Smoke Curtains may also be applicable in a fixed position for factory, industrial, and storage classified buildings that are not equipped with a sprinkler system. In these applications the fixed draft curtains are suspended from the underside of the roof for at least four to six feet depending on the classification designation called for by the local building code. The maximum area being protected by the draft curtains depends on the occupancy group (Type F – Factory Industrial Group; Type S – Storage Group) and overall height of storage within the building.
Smoke and Fire Protective Curtain Assemblies consist of several basic components and configuration requirements. As indicated under the “Components” article in Part 2 of this section, the curtain fabric is typically woven together and consists of materials such as glass fiber cloth, aluminum coatings and stainless steel thread that can provide the necessary fire rating and varies depending on the specific manufacturer. The fire curtain must comply with the designated fire tests of UL 10D and UL 263, and have the specified flame spread index and smoke developed index of ASTM E84. The depth of the fixed smoke draft curtain shall be indicated, and if the assembly is deployable the type of application needs to be specified from the following list:
- Fabric draft curtain system
- Fire-protective smoke curtain
- Fire-protective smoke curtain with egress
- Fire-protective smoke curtain ICC-ES AC77 compliant with egress
- Fire-protective smoke curtain with accordion style for corner conditions, and egress choice option
- Fire-protective smoke curtain horizontal-deploying system compliant with NFPA 288
The fire rating may be designated to comply with either UL 10C (positive pressure fire test), or UL 10B (neutral or negative pressure fire test) without the hose stream test. Current fire tests are generally based on the positive pressure fire test as that is considered to be a more accurate representation of actual conditions. The hose stream test is not applicable for fabric curtains. There are numerous choice options provided for the “Fire Rating” from 20 minutes to three hours, or the “As indicated on drawings” option. “Smoke and Draft Control” is typically required for elevator hoistway door applications in order to comply with the “S” label requirements regarding maximum air leakage around the curtain in compliance with UL 1784. In order to maintain the smoke and fire separation, the curtain must either be continuous from edge to edge in the closed position, or provided in segmented widths with an overlap that still maintains the necessary air seal. An applicable UL label shall be affixed to the curtain assembly, and the height and width of the curtain may also be specified under “Components” article, or indicated on the drawings.
Smoke and Fire Curtain is supported on a roller assembly enclosed within a painted metal hood assembly. The roller may have a circular or octagonal tube shape of stainless or galvanized steel. For curtains exceeding 18 feet in width a double roller is required. These two rollers may be set up side to side or over/under to each other depending on plenum space available. The size of a single roller hood with a 3 foot drop is only 5 inches by 5 inches. A curtain with an over/under double roller and a 65 foot drop is only 11 inches by 20 inches. Verify actual hood assembly sizes with curtain manufacturer. Connected to the roller is a motor drive unit that is used to reopen the curtain and control its speed of decent. There are various options for installation of the hood assembly; suspended by threaded rods from metal decking, bolted to an I-beam, or mounted from the back or top side of enclosure. There are also options for finished ceiling opening; flush, shadow gap, or downstand neck. The vertical guides, with a 3/8 inch wide gap, that support each edge of curtain may have a flush or exposed configuration, and internally concealed UL approved smoke seals. A tubular bar is attached to the bottom of curtain with needed stiffness to limit deflection that may occur from building’s air pressure currents and to maintain a taut and level curtain when fully extended. For some applications egress through the curtain may be necessary, such as at elevator door and lobby corridor locations. These egress openings are called out to comply with ICC Evaluation Services Acceptance Criteria 77 (ICC-ES AC77), and typically curtain manufacturers are in compliance with this criteria. The egress options indicated include; a pass-through slot at overlapping curtains (this does not comply with AC77), a manual lift of curtain using an integral strap requiring 15 pounds or less of uplift force, and rewind switches located at both sides of deployed curtain to manually activate the curtain to open.
Curtain operational controls are generally Factory Mutual (FM), Intertek Testing Services (ITS), or UL listed products. The curtain is set-up to deploy within 10 seconds after receiving actuation signal from building fire alarm, local smoke detection, sprinkler alarm system, or due to loss of electric power to unit. To protect against having the curtain come down on something or someone, it should be capable of sensing an object in its downward path and stop until object is removed. As previously indicated as an egress option, rewind switches may be wall mounted, and some manufacturers provide this switch within the curtain fabric on each side. To accommodate for loss of power situations, a battery backup system may be required. An electric motor with gearbox assembly is located within the hood and attached to the roller assembly. The motor controls contain electromechanical travel limit switches linked to electromagnetic brakes in compliance with NFPA 70. Power is typically supplied off the buildings 120 VAC power supply and motors run on 24 VDC. Motor is typically providing a curtain descent speed within range of 6 to 24 inches per second. A group control panel is set up to be synced and integrated with building emergency systems and capable of controlling multiple curtain motors. Test features should be provided for the operational controls to verify curtain is functioning correctly. A fail-safe release device may also be provided for curtain. This device will close the curtain by gravity drop upon loss of building power and/or auxiliary power. It may also be programmed to close with time delay after power failure if fire and smoke alarm condition is not called for. Upon restoration of power and with cleared alarm condition the curtain will reset to open position.
Prior to installation, the existing conditions should be verified to ensure proper installation conditions are being provided. Coordination of other disciplines is required for installation of curtains and operational controls. Conduits, wiring of controls and equipment, and integration with fire suppression sprinkler system, fire alarms and smoke detection systems is required. Field testing and inspection is also necessary to confirm that curtains deploy and function properly. It is also beneficial to provide for ongoing maintenance and periodic inspections of these Smoke and Fire Protective Curtain Assemblies in accordance with the applicable reference standards to ensure they operate properly now and in the future.
Editing of Section 08 3477 – Smoke and Fire Protective Curtain assemblies is designed to start in PART 2 - PRODUCTS, progress to PART 3 - EXECUTION, and finish up with PART 1 - GENERAL. The various types of curtains, related components, and operational controls comprise the main articles in PART 2.
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