Title: Section 905 • Size: 57807
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905.1 Scope and Purpose. This section applies to mechanical or passive smoke-control systems when they are required by other provisions of this code. The purpose of this chapter is to establish minimum requirements for the design, installation and acceptance testing of smoke-control systems which are intended to provide a tenable environment for the evacuation or relocation of occupants. These provisions are not intended for the preservation of contents or for assistance in fire-suppression or overhaul activities. Smoke-control systems need not comply with the requirements of Section 609 in the Mechanical Code unless their normal use would otherwise require compliance. Nothing within these requirements is intended to apply when smoke control is not otherwise required by this code. Smoke-control systems are not a substitute for sprinkler protection.
905.2 Design Methods.
905.2.1 General. Buildings or portions thereof required by this code to have a smoke-control system shall have such systems designed in accordance with the requirements of this section.
EXCEPTION: Smoke and heat venting required by Section 906.
905.2.2.1 General. Systems or methods of construction to be used in smoke control shall be based on a rational analysis in accordance with well-established principles of engineering. The analysis shall include, but not be limited by, Sections 905.2.2.2 through 905.2.2.6 below.
905.2.2.2 Stack effect. The system shall be designed such that the maximum probable normal or reverse stack effects will not adversely interfere with the system's capabilities. In determining the maximum probable stack effects, altitude, elevation, weather history and interior temperatures shall be used.
905.2.2.3 Temperature effect of fire. Buoyancy and expansion caused by the design fire (Section 905.6) shall be analyzed. The system shall be designed such that these effects do not adversely interfere with the system's capabilities.
905.2.2.4 Wind effect. The design shall consider the adverse effects of wind. Such consideration shall be consistent with the requirements of Chapter 16, Part II-Wind Design.
905.2.2.5 HVAC systems. The design shall consider the effects of the heating, ventilating and air-conditioning (HVAC) systems on both smoke and fire transport. The analysis shall include all permutations of systems status. The design shall consider the effects of the fire on the heating, ventilating and air-conditioning systems.
905.2.2.6 Climate. The design shall consider the effects of low temperatures on systems, property and occupants. Air inlets and exhausts shall be located so as to prevent snow or ice blockage.
905.2.3 Smoke barrier construction. A smoke barrier may or may not have a fire-resistive rating. Smoke barriers shall be constructed and sealed to limit leakage areas exclusive of protected openings. Maximum allowable leakage area shall be the aggregate area calculated using the following leakage area ratios:
2. Exit enclosures:
3. All other shafts:
4. Floors and roofs:
A = total leakage area, square feet ().
= unit floor or roof area of barrier, square feet ().
= unit wall area of barrier, square feet ().
Total leakage area of the barrier is then the product of the smoke barrier gross area times the allowable leakage area ratio. Compliance shall be determined by achieving the minimum air pressure difference across the barrier with the system in the smoke-control mode for mechanical smoke-control systems. Passive smoke-control systems may be tested using other approved means such as door fan testing.
905.2.4 Opening protection. Openings in smoke barriers shall be protected by automatic-closing devices actuated by the required controls for the mechanical smoke-control system.
EXCEPTIONS: 1. Passive smoke-control systems may have automatic-closing devices actuated by spot-type smoke detectors listed for releasing service.
2. The airflow method may be used to protect fixed openings between smoke zones.
Door openings shall be protected by an unlouvered tight-fitting smoke- and draft-control assembly having a fire-protection rating of not less than 20 minutes when tested in accordance with U.B.C. Standard 7-2. The door and frame shall bear an approved label or other identification showing the rating thereof, the name of the manufacturer and the identification of the service conducting the inspection of materials and workmanship at the factory during fabrication and assembly. Doors shall be maintained self-closing or shall be automatic-closing by actuation of a smoke detector in accordance with Section 713.2. Smoke- and draft-control door assemblies shall be provided with a gasket so installed as to provide a seal where the door meets the stop on both sides, across the top and at the sill.
EXCEPTIONS: 1. In Group I, Division 1 Occupancies when such doors are installed across corridors, a pair of opposite-swinging doors without a center mullion shall be installed having vision panels with approved fire-rated glazing materials in approved fire-rated frames, the area of which shall not exceed that tested. The doors shall be close fitting within operational tolerances, and shall not have undercuts, louvers or grilles. The doors shall have head and jamb stops, astragals or rabbets at meeting edges and automatic-closing devices. Positive latching devices may be omitted.
2. Group I, Division 3 Occupancies.
Duct and other heating, ventilating and air-conditioning openings shall be equipped with a minimum Class II, 250°F. (121°C.) smoke damper as defined and tested in accordance with approved recognized standards. See Chapter 35, Part III.
905.2.5 Duration of operation. All portions of active or passive smoke-control systems shall be capable of continued operation after detection of the fire event for not less than 20 minutes.
905.3 Pressurization Method.
905.3.1 General. The primary means of controlling smoke shall be pressure differences across smoke barriers. Maintenance of a tenable environment is not required in the smoke-control zone of fire origin.
905.3.2 Minimum pressure difference. The minimum pressure difference across a smoke barrier shall be 0.05 inch water gage (12.4 Pa) in fully sprinklered buildings.
EXCEPTION: Smoke-control systems serving other than fully sprinklered buildings may be approved by the building official provided the system is designed to achieve pressure differences at least two times the maximum calculated pressure difference produced by the design fire.
905.3.3 Maximum pressure
difference. The maximum air pressure difference
across a smoke barrier shall be determined by required door-opening
forces. The actual force required to open exit doors when the
system is in the smoke-control mode shall be in accordance with
Section 1004. The calculated
force to set a side-hinged, swinging door in motion shall be determined
A = door area, square feet ().
d = distance from door handle to latch edge of door, feet (m).
F = total door opening force, pounds (N).
= force required to overcome closing device, pounds (N).
K = 5.2 (9.6).
W = door width, feet (m).
= design pressure difference, inches (mm) water gage.
Opening forces for other doors shall be determined by standard engineering methods for the resolution of forces and reactions.
905.4 Airflow Method.
905.4.1 General. When approved by the building official, smoke may be prevented from migrating through fixed openings between smoke-control zones by the use of the airflow method. The design airflows shall be in accordance with this section.
905.4.2 Velocity. The minimum average velocity through a fixed opening shall not be less than:
h = height of opening, feet (m).
= temperature of smoke, °F. (K).
= temperature of ambient air, °F. (K).
v = air velocity, feet per minute (m/s).
Airflow shall be directed to limit smoke migration from the fire zone. The geometry of openings shall be considered to prevent flow reversal from turbulent effects.
905.4.3 Prohibited conditions. This method shall not be employed where either the quantity of air or the velocity of the airflow will adversely affect other portions of the smoke-control system, unduly intensify the fire, disrupt plume dynamics or interfere with exiting. In no case shall airflows toward the fire exceed 200 feet per minute (60 960 mm per minute). Where Formula (5-2) requires airflows to exceed this limit, the airflow method shall not be used.
905.5 Exhaust Method.
905.5.1 General. When approved by the building official, for large enclosed volume, such as in atria or malls, the exhaust method may be used. The design exhaust volumes shall be in accordance with this section.
905.5.2 Exhaust rate.
905.5.2.1 General. The height of the lowest horizontal surface of the accumulating smoke layer shall be maintained at least 10 feet (3048 mm) above any walking surface within the smoke zone. The required exhaust rate for the zone shall be the largest of the calculated plume mass flow rates for the possible plume configurations. Provisions shall be made for natural or mechanical supply of outside air to make up an equal volume of the air exhausted at flow rates not to exceed 200 feet per minute (60 960 mm per minute) toward the fire.
plumes. The plume mass flow rate [,
lbs./sec. (kg/s)] shall be determined by placing the design fire
center on the axis of the space being analyzed. The limiting flame
height shall be determined by:
Q = total heat output.
= convective heat output, Btu/s (kW). (The value of shall not be taken as less than 0.70Q.)
z = height from top of fuel surface to bottom of smoke layer, feet (m).
= limiting flame height, feet (m). (must be greater than the fuel equivalent diameter. See Section 905.6.)
for z >
for z =
for z <
To convert from pounds per second of mass flow to a volumetric rate, the following formula shall be used:
V = volumetric flow rate, cubic feet per minute (/s).
= density of air at the temperature of the smoke layer, lbs./ (T:in °F.) [kg/ (T:in°C.)].
905.5.2.3 Balcony spill plumes. The plume mass flow rate () for spill plumes shall be determined using the geometrically probable width based on architectural elements and projections in the following formula:
H = height above fire to underside of balcony, feet (m).
W = plume width at point of spill, feet (m).
= height from balcony, feet (m).
905.5.2.4 Window plumes. The plume mass flow rate () shall be determined from:
= area of the opening, square feet ().
= height of the opening, feet (m).
= height from the top of the window or opening to the bottom of the smoke layer, feet (m).
905.5.2.5 Plume contact with walls. When the axisymmetric plume contacts the surrounding walls, the mass flow rate may be considered to be constant from the point of contact and beyond provided that contact remains constant. Use of this provision requires calculation of the plume diameter, which shall be calculated by:
d = plume diameter, feet (m).
= ambient air temperature, °F. (K).
|= plume centerline temperature, °F. (K).|
z = height at which is determined, feet (m).
905.6 Design Fire.
905.6.1 General. The design fire shall be based on a Q of not less than 5,000 Btu per second (5275 kW) unless a rational analysis is performed by the designer and approved by the building official.
905.6.2 Rational analysis.
905.6.2.1 Factors considered. The engineering analysis shall include the characteristics of the fuel, fuel load, effects included by the fire, whether the fire is likely to be steady or unsteady.
905.6.2.2 Separation distance. Determination of the design fire shall include consideration of the type of fuel, fuel spacing and configuration. The design fire shall be increased if other combustibles are within the separation distance as determined by:
= incident radiant heat flux required for nonpiloted ignition, .
Q = heat release from fire, Btu/s (kW).
R = separation distance from target to center of fuel package, feet (m).
The ratio of the separation distance to the fuel equivalent radius shall not be less than 4. The fuel equivalent radius shall be the radius of a circle of equal area to floor area of the fuel package.
905.6.2.3 Heat-release assumptions. The analysis shall make use of best available data and shall not be based on excessively stringent limitations of combustible material. For offices, the heat release rate shall be or greater. For mercantile and residential occupancies, the heat release rate shall be or greater.
905.6.2.4 Sprinkler effectiveness assumptions. The effect of sprinklers may be assumed to have halted fire growth at time of activation only upon a documented engineering analysis.
905.7.1 General. Equipment such as, but not limited to, fans, ducts and balance dampers shall be suitable for their intended use, suitable for the probable temperatures to which they may be exposed and approved by the building official.
905.7.2 Exhaust fans. Components of exhaust fans shall be rated and certified by the manufacturer for the probable temperature rise to which the components may be exposed. This temperature rise shall be computed by:
c = specific heat of smoke at smoke-layer temperature, Btu/lb.°F. (kJ/kg-K).
m = exhaust rate, pounds per second (kg/s).
= convective heat output of fire, Btu/sec. (kW).
= ambient temperature, °F. (K).
= smoke temperature, °F. (K).
EXCEPTION: may be reduced if dilution air is assured and the new is calculated.
905.7.3 Ducts. Duct materials and joints shall be capable of withstanding the probable temperatures and pressures to which they are exposed as determined by Formula (5-13). Ducts shall be constructed and supported in accordance with the Mechanical Code. Ducts shall be leak tested to 1.5 times the maximum design pressure in accordance with nationally accepted practices. Measured leakage shall not exceed 5 percent of design flow. Results of such testing shall be a part of the documentation procedure. Ducts shall be supported directly from fire-resistive structural elements of the building by substantial, noncombustible supports.
EXCEPTION: Flexible connections, for the purpose of vibration isolations complying with the Mechanical Code, may be used if constructed of approved fire-resistive materials.
905.7.4 Equipment, inlets and outlets. Equipment shall be located so as to not expose uninvolved portions of the building to an additional fire hazard. Outside air inlets shall be located so as to minimize the potential for introducing smoke or flame into the building. Exhaust outlets shall be so located as to minimize reintroduction of smoke into the building and to limit exposure of the building or adjacent buildings to an additional fire hazard.
905.7.5 Automatic dampers. Automatic dampers installed within the smoke-control system shall be listed and conform to the requirements of approved recognized standards. See Chapter 35, Part III.
905.7.6 Fans. In addition to other requirements, belt-driven fans shall have 1.5 times the number of belts required for the design duty with the minimum number of belts being two. Fans shall be selected for stable performance based on normal temperature and, where applicable, elevated temperature. Calculations and manufacturer's fan curves shall be part of the documentation procedures. Fans shall be supported and restrained by noncombustible devices in accordance with the requirements of Chapter 16. Motors driving fans shall not be operating beyond their name plate horsepower (kilowatts) as determined from measurement of actual current draw. Motors driving fans shall have a minimum service factor of 1.15.
905.8 Power Systems.
905.8.1 General. The smoke-control system shall be supplied with two sources of power. Primary power shall be the normal building power systems. Secondary power shall be from an approved standby source complying with the Electrical Code. The standby power source and its transfer switches shall be in a separate room from the normal power transformers and switchgear and shall be enclosed in a room of not less than one-hour fire-resistive construction, ventilated directly to and from the exterior. Power distribution from the two sources shall be by independent routes.
Transfer to full standby power shall be automatic and within 60 seconds of failure of the primary power. The systems shall comply with the Electrical Code.
905.8.2 Power sources and power surges. Elements of the smoke-management system relying on volatile memories or the like shall be supplied with uninterruptable power sources of sufficient duration to span 15-minute primary power interruption. Elements of the smoke-management system susceptible to power surges shall be suitably protected by conditioners, suppressors or other approved means.
905.9 Detection and Control Systems.
905.9.1 General. Fire-detection and control systems for mechanical smoke-control systems shall be supervised in accordance with the Fire Code. Supervision shall include positive confirmation of actuation, testing, manual override, and the presence of power downstream of all disconnects.
905.9.2 Wiring. In addition to meeting requirements of the Electrical Code, all wiring, regardless of voltage, shall be fully enclosed within continuous raceways.
905.9.3 Activation. Smoke-control systems shall be activated as follows:
1. Mechanical smoke-control systems, using the pressurization method, serving buildings having no occupied floor more than 300 feet (91 440 mm) above or 75 feet (22 860 mm) below exit grade shall have automatic control of pressurized stairwell enclosure systems. All other portions of the smoke-control system may be manual in accordance with Section 905.12.
EXCEPTION: When required in Group I Occupancies, they shall be entirely automatic.
2. Mechanical smoke-control systems, using the pressurization method, serving buildings having occupied floors more than 300 feet (91 440 mm) above or 75 feet (22 860 mm) below exit grade shall have completely automatic control.
3. Mechanical smoke-control systems using the airflow or exhaust method shall have completely automatic control.
4. Passive smoke-control systems may be actuated by approved spot-type detectors listed for releasing service.
905.9.4 Automatic control. Whenever completely automatic control is required or used, the automatic-control sequences shall be initiated from an appropriately zoned automatic sprinkler system meeting the requirements of U.B.C. Standard 9-1 or from an appropriately zoned, total coverage smoke-detection system meeting the requirements of the Fire Code.
905.9.5 Smoke detection. Smoke detectors shall be listed and shall be installed in accordance with the Fire Code.
905.10 Control Air Tubing.
905.10.1 General. Control-air tubing shall be of sufficient size to meet the required response times. Tubing shall be flushed clean and dry prior to final connections. Tubing shall be adequately supported and protected from damage. Tubing passing through concrete or masonry shall be sleeved and protected from abrasion and electrolytic action.
905.10.2 Materials. Control-air tubing shall be hard drawn copper, Type L, ACR, see ASTM B 42-92, B 43-91, B 68-88, B 88-92, B 251-88 and B 280-92. Fittings shall be wrought copper or brass, solder type, see ANSI B16.22-89 or ANSI B16.18-84. Changes in direction may be made with appropriate tool bends. Brass, compression-type fittings may be used at final connection to devices; other joints shall be brazed using a brazing alloy with solidus above 1,100°F. (593°C.) and liquidus below 1,500°F. (816°C.) Brazing flux shall be used on copper to brass joints only.
EXCEPTION: Nonmetallic tubing may be used within control panels and at the final connection to devices providing all of the following conditions are met:
1. Tubing shall be listed by an approved agency for flame and smoke characteristics.
2. Tubing and connected device shall be completely enclosed within galvanized or paint grade steel enclosure of not less than 0.030 inch (0.76 mm) (No. 22 galvanized sheet gage) thickness. Entry to the enclosure shall be by copper tubing with a protective grommet of neoprene or teflon or by suitable brass compression to male barbed adapter.
3. Tubing shall be identified by appropriately documented coding.
4. Tubing shall be neatly tied and supported within enclosure. Tubing bridging cabinet and door or moveable device shall be of sufficient length to avoid tension and excessive stress. Tubing shall be protected against abrasion. Tubing serving devices on doors shall be fastened along hinges.
905.10.3 Isolation from other functions. All control tubing serving other than smoke-control functions shall be isolated by automatic isolation valves or shall be an independent system.
905.10.4 Testing. Test all control-air tubing at three times operating pressure for not less than 30 minutes without any noticeable loss in gage pressure prior to final connection to devices.
905.11 Marking and Identification. The detection and control systems shall be clearly marked at all junctions, accesses and terminations.
905.12 Control Diagrams. Identical control diagrams showing all devices in the system and identifying their location and function shall be maintained current and kept on file with the building official, the fire department and in the central control station in an approved format and manner.
905.13 Firefighter's Control Panel.
905.13.1 General. A firefighter's control panel shall be provided for manual control or override of automatic control for mechanical smoke-control systems. Such panel shall be designed to graphically depict the building arrangement and smoke-control system zones served by the systems. The status of each smoke-control zone shall be indicated by lamps and appropriate legends.
Fans, major ducts and dampers within the building that are portions of the smoke-control systems shall be shown on the firefighter's control panel and shall be shown connected to their respective ducts with a clear indication of the direction of airflow.
Devices, switches, indicators and the like shall bear plain English identifying legends having a size and stroke equivalent to 12 point helvetica bold.
Status indicators shall be provided for all smoke-control equipment by pilot lamp-type indicators as follows:
1. Fans, dampers and other operating equipment in their normal status-YELLOW.
2. Fans, dampers and other operating equipment in their off or closed status-RED.
3. Fans, dampers and other operating equipment in their on or open status-GREEN.
4. Fans, dampers and other operating equipment in a fault status-AMBER/ORANGE.
Provision for testing the pilot lamp on the firefighter's control panel by means of one or more "lamp test" momentary push buttons or other self-restoring means shall be included.
The fault status shall be further identified by pulsing the indicator lamp.
EXCEPTION: Light-emitting diodes may be used in lieu of pilot lamps with prior approval.
The firefighter's control panel layout shall be submitted at full scale for approval prior to installation.
905.13.2 Smoke-control capability. The firefighter's control panel shall provide control capability over the complete smoke-control system equipment within the building as follows:
1. ON-AUTO-OFF control over each individual piece of operating smoke-control equipment that can also be controlled from other sources within the building. This includes stairway pressurization fans; smoke exhaust fans; supply, return and exhaust fans; elevator shaft fans; and other operating equipment used or intended for smoke-control purposes.
2. OPEN-AUTO-CLOSE control over all individual dampers relating to smoke control and that are also controlled from other sources within the building.
3. ON-OFF or OPEN-CLOSE control over all smoke-control and other critical equipment associated with a fire or smoke emergency and that can only be controlled from the firefighter's control panel.
EXCEPTIONS: 1. For complex systems, with prior approval, the controls and indicators may be combined to control and indicate all elements of a single smoke zone as a unit.
2. For complex systems, with prior approval, the control may be accomplished by computer interface using approved, plain English commands.
905.13.3 Control action and priorities. The firefighter's control panel actions shall be as follows:
1. ON-OFF, OPEN-CLOSE control actions shall have the highest priority of any control point within the building. Once issued from the firefighter's control panel, no automatic or manual control from any other control point within the building shall contradict the control action.
Where automatic means is provided to interrupt normal, nonemergency equipment operation or produce a specific result to safeguard the building or equipment (i.e., duct freezestats, duct smoke detectors, high-temperature cutouts, temperature-actuated linkage and similar devices), such means shall be capable of being overridden by the firefighter's control panel control action and the last control action as indicated by each firefighter's control panel switch position shall prevail.
EXCEPTION: Power disconnects required by the Electrical Code.
2. Only the AUTO position of each three-position firefighter's control panel switch shall allow automatic or manual control action from other control points within the building. The AUTO position shall be the NORMAL, nonemergency, building control position. When a firefighter's control panel is in the AUTO position, the actual status of the device (on, off, open, closed) shall continue to be indicated by the status indicator described above.
905.14 Response Time. Smoke-control system activation shall be initiated immediately after receipt of an appropriate automatic or manual activation command. Smoke-control systems shall activate individual components (such as dampers and fans) in the sequence necessary to prevent physical damage to the fans, dampers, ducts and other equipment. The total response time for individual components to achieve their desired operating mode shall not exceed the following:
|1. Control air isolation valves||Immediately|
|2. Smoke damper closing||15 seconds|
|3. Smoke damper opening||15 seconds maximum|
|4. Fan starting (energizing)||15 seconds maximum|
|5. Fan stopping (de-energizing)||Immediately|
|6. Fan volume modulation||30 seconds maximum|
|7. Pressure control modulation||15 seconds maximum|
|8. Temperature control safety override||Immediately|
|9. Positive indication of status||15 seconds maximum|
For purposes of smoke control, the firefighter's control panel response time shall be the same for automatic or manual smoke-control action initiated from any other building control point.
905.15 Acceptance Testing.
905.15.1 General. Devices, equipment, components and sequences shall be individually tested. These tests, in addition to those required above or by other provisions of this code, shall consist of determination of function, sequence and, where applicable, capacity of their installed condition.
905.15.2 Detection devices. Smoke or fire detectors which are a part of a smoke-control system shall be tested in accordance with the Fire Code in their installed condition. When applicable, this testing shall include verification of airflow in both minimum and maximum conditions.
905.15.3 Ducts. Ducts which are part of a smoke-control system shall be traversed using generally accepted practices to determine actual air quantities.
905.15.4 Dampers. Dampers shall be tested for function in their installed condition.
905.15.5 Inlets and outlets. Inlets and outlets shall be read using generally accepted practices to determine air quantities.
905.15.6 Fans. Fans shall be examined for correct rotation. Measurements of voltage, amperage, revolutions per minute and belt tension shall be made.
905.15.7 Smoke barriers. Measurements using inclined manometers shall be made of the pressure differences across smoke barriers. Such measurements shall be conducted for each possible smoke-control condition.
905.15.8 Controls. Each smoke zone, equipped with an automatic initiation device, shall be put into operation by the actuation of one such device. Each additional such device within the zone shall be verified to cause the same sequence but the operation of fan motors may be bypassed to prevent damage.
Control sequences shall be verified throughout the system, including verification of override from the firefighter's control panel and simulation of standby power conditions.
905.15.9 Reports. A complete report of testing shall be prepared by the required special inspector or special inspection agency. The report shall include identification of all devices by manufacturer, nameplate data, design values, measured values and identification tag or mark. The report shall be reviewed by the responsible designer, and when satisfied that the design intent has been achieved, the responsible designer shall affix the designer's signature and date to the report with a statement as follows:
I have reviewed this report and by personal knowledge and on-site observation certify that the smoke-control system is in substantial compliance with the design intent, and to the best of my understanding complies with requirements of the code.
A copy of the final report shall be filed with the building official and an identical copy shall be maintained in an approved location at the building.
905.15.10 Identification and documentation. Charts, drawings and other documents identifying and locating each component of the smoke-control system, and describing their proper function and maintenance requirements shall be maintained on file at the building with the above-described report.
Devices shall have an approved identifying tag or mark on them consistent with the other required documentation and shall be dated indicating the last time they were successfully tested and by whom.
905.16 Acceptance. Buildings, or portions thereof, required by this code to comply with this chapter shall not be issued a certificate of occupancy until such time that the building official determines that the provisions of this chapter have been fully complied with and that the fire department has received satisfactory instruction on the operation, both automatic and manual, of the system.
EXCEPTION: In buildings
of phased construction, the building official may issue a temporary
certificate of occupancy if those portions of the building to
be occupied meet the requirements of this chapter and that the
remainder does not pose a significant hazard to the safety of
the proposed occupants or adjacent buildings.
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