Current through Register 1531, September 27, 2024
Where required by Section 1022.9, a smokeproof enclosure
shall be constructed in accordance with this section. A smokeproof enclosure
shall consist of an enclosed interior exit
stairway that conforms to Section 1022.1 and an open exterior
balcony or ventilated vestibule meeting the requirements of this section. Where
access to the roof is required by the International Fire Code,
such access shall be from the smokeproof enclosure where a smokeproof enclosure
is required.
909.20.1
Access. Access to the stair shall be by way of a
vestibule or an open exterior balcony. The minimum dimension of the vestibule
shall not be less than the required width of the corridor
leading to the vestibule but shall not have a width of less than 44 inches
(1118 mm) and shall not have a length of less than 72 inches (1829 mm) in the
direction of egress travel.
909.20.2
Construction. The
smokeproof enclosure shall be separated from the remainder of the building by
not less than 2-hour fire barriers constructed in accordance
with Section 707 or horizontal assemblies constructed in
accordance with Section 712, or both. Openings are not permitted other than the
required means of egress doors. The vestibule shall be
separated from the stairway by not less than 2-hour
fire barriers constructed in accordance with Section 707 or
horizontal assemblies constructed in accordance with Section
712, or both. The open exterior balcony shall be constructed in accordance with
the fire-resistance rating requirements for floor assemblies.
909.20.2.1
Door closers. Doors
in a smokeproof enclosure shall be self- or automatic closing by actuation of a
smoke detector in accordance with Section 715.4 and shall be installed at the
floor-side entrance to the smokeproof enclosure. The actuation of the smoke
detector on any door shall activate the closing devices on all doors in the
smokeproof enclosure at all levels. Smoke detectors shall be installed in
accordance with Section 907.3.
909.20.3
Natural ventilation
alternative. The provisions of Sections 909.20.3.1 through 909.20.3.3
shall apply to ventilation of smokeproof enclosures by natural means.
909.20.3.1
Balcony doors. Where
access to the stairway is by way of an open exterior balcony,
the door assembly into the enclosure shall be a fire door
assembly in accordance with Section 715.4.
909.20.3.2
Vestibule doors.
Where access to the stairway is by way of a vestibule, the
door assembly into the vestibule shall be a fire door
assembly complying with Section 715.4. The door assembly from
the vestibule to the stairway shall have not less than a
20-minute fire protection rating complying with Section
715.4.
909.20.3.3
Vestibule
ventilation. Each vestibule shall have a minimum net area of 16 square
feet (1.5 m2) of opening in a wall facing an outer
court, yard or public way
that is at least 20 feet (6096 mm) in width.
909.20.4
Mechanical ventilation
alternative. The provisions of Sections 909.20.4.1 through 909.20.4.4
shall apply to ventilation of smokeproof enclosures by mechanical means.
909.20.4.1
Vestibule doors. The
door assembly from the building into the vestibule shall be a fire
door
assembly complying with Section 715.4.3. The
door assembly from the vestibule to the stairway shall not
have less than a 20-minute fire protection rating and meet the
requirements for a smoke door assembly in accordance with Section 715.4.3. The
door shall be installed in accordance with NFPA 105.
909.20.4.2
Vestibule
ventilation. The vestibule shall be supplied with not less than one air
change per minute and the exhaust shall not be less than 150 percent of supply.
Supply air shall enter and exhaust air shall discharge from the vestibule
through separate, tightly constructed ducts used only for that purpose. Supply
air shall enter the vestibule within 6 inches (152 mm) of the floor level. The
top of the exhaust register shall be located at the top of the smoke trap but
not more than 6 inches (152 mm) down from the top of the trap, and shall be
entirely within the smoke trap area. Doors in the open position shall not
obstruct duct openings. Duct openings with controlling
dampers
are permitted where necessary to meet the design requirements, but
dampers are not otherwise required.
909.20.4.2.1
Engineered ventilation
system. Where a specially engineered system is used, the system shall
exhaust a quantity of air equal to not less than 90 air changes per hour from
any vestibule in the emergency operation mode and shall be sized to handle
three vestibules simultaneously. Smoke detectors shall be located at the
floor-side entrance to each vestibule and shall activate the system for the
affected vestibule. Smoke detectors shall be installed in accordance with
Section 907.3.
909.20.4.3
Smoke trap. The
vestibule ceiling shall be at least 20 inches (508 mm) higher than the door
opening into the vestibule to serve as a smoke and heat trap and to provide an
upward-moving air column. The height shall not be decreased unless
approved and justified by design and test.
909.20.4.4
Stair shaft air movement
system. The stair shaft shall be provided with a
dampered relief opening and supplied with sufficient air to maintain a minimum
positive pressure of 0.10 inch of water (25 Pa) in the shaft relative to the
vestibule with all doors closed.
909.20.5
Stair pressurization
alternative. Where the building is equipped throughout with an
automatic sprinkler system in accordance with Section
903.3.1.1, the vestibule is not required, provided that interior
exit
stairways are pressurized to a minimum
of 0.10 inch of water (25 Pa) and a maximum of 0.35 inch of water (87 Pa) in
the shaft relative to the building measured with all stairway
doors closed under maximum anticipated conditions of stack effect and wind
effect.
909.20.6
Ventilating
equipment. The activation of ventilating equipment required by the
alternatives in Sections 909.20.4 and 909.20.5 shall be by smoke detectors
installed at each floor level at an approved location at the
entrance to the smokeproof enclosure. When the closing device for the
stair shaft and vestibule doors is activated by smoke
detection or power failure, the mechanical equipment shall activate and operate
at the required performance levels. Smoke detectors shall be installed in
accordance with Section 907.3.
909.20.6.1
Ventilation systems. Smokeproof enclosure ventilation systems
shall be independent of other building ventilation systems. The equipment,
control wiring, power wiring and ductwork shall comply with one of the
following:
1. Equipment, control wiring, power
wiring and ductwork shall be located exterior to the building and directly
connected to the smokeproof enclosure or connected to the smokeproof enclosure
by ductwork enclosed by not less than 2-hour fire barriers
constructed in accordance with Section 707 or horizontal
assemblies constructed in accordance with Section 712, or
both.
2. Equipment, control wiring,
power wiring and ductwork shall be located within the smokeproof enclosure with
intake or exhaust directly from and to the outside or through ductwork enclosed
by not less than 2-hour fire barriers constructed in
accordance with Section 707 or horizontal assemblies
constructed in accordance with Section 712, or both.
3. Equipment, control wiring, power wiring
and ductwork shall be located within the building if separated from the
remainder of the building, including other mechanical equipment, by not less
than 2-hour fire barriers constructed in accordance with
Section 707 or horizontal assemblies constructed in accordance
with Section 712, or both.
Exceptions:
1. Control wiring and power wiring utilizing
a 2-hour rated cable or cable system.
2. Where encased with not less than 2 inches
(51 mm) of concrete.
909.20.6.2
Standby power.
Mechanical vestibule and stair shaft ventilation systems and
automatic fire detection systems shall be powered by an
approved standby power system conforming to Section 403.4.7
and Chapter 27.
909.20.6.3
Acceptance and testing. Before the mechanical equipment is
approved, the system shall be tested in the presence of the
building official to confirm that the system is operating in
compliance with these requirements.
