Chapter 10 Means of Egress

Except as specifically provided for in this chapter, no employer or agent of such employer shall lock the doors of or otherwise prohibit exit from any workplace, when by so doing the health or safety of any employee, independent contractor or other individual working in such workplace may become endangered by fire or other hazardous condition. Refer to Article 307 of Title 28 of the Administrative Code.

Every existing structure which is not provided with means of egress as required by this chapter and, in which the means of egress are, in the opinion of the commissioner, inadequate for the safety of the occupants, shall be provided with means of egress or fire protection as directed by the commissioner.

The following terms are defined in Chapter 2:

ACCESSIBLE MEANS OF EGRESS.

AISLE.

AISLE ACCESSWAY.

ALTERNATING TREAD DEVICE.

AREA OF RESCUE ASSISTANCE.

ASSEMBLY SPACE.

ASSISTED RESCUE PATH.

BLEACHERS.

BREAKOUT.

COMMON PATH OF EGRESS TRAVEL.

CORRIDOR.

CORRIDOR, INTERIOR.

CORRIDOR, PUBLIC.

CROSS AISLE.

DEAD END. 

DOOR, BALANCED.

EGRESS COURT.

EMERGENCY ESCAPE AND RESCUE OPENING.

EXIT.

EXIT ACCESS.

EXIT ACCESS DOORWAY.

EXIT ACCESS RAMP.

EXIT ACCESS STAIRWAY.

EXIT DISCHARGE.

EXIT DISCHARGE, LEVEL OF.

EXIT, HORIZONTAL.

EXIT PASSAGEWAY.

EXTERIOR EXIT RAMP.

EXTERIOR EXIT STAIRWAY.

FIRE EXIT HARDWARE.

FIXED SEATING.

FLIGHT.

FLOOR AREA, GROSS.

FLOOR AREA, NET.

FOLDING AND TELESCOPIC SEATING.

GRANDSTAND.

GUARD.

HANDRAIL.

INTERIOR EXIT RAMP.

INTERIOR EXIT STAIRWAY.

LOW ENERGY POWER-OPERATED DOOR.

MEANS OF EGRESS.

MERCHANDISE PAD.

NOSING.

OCCUPANT LOAD.

OCCUPANT SENSOR.

OPEN-ENDED CORRIDOR.

PANIC HARDWARE.

PHOTOSENSOR.

POWER-ASSISTED DOOR.

POWER-OPERATED DOOR.

PUBLIC WAY.

RAMP.

REFUGE AREA.

SCISSOR STAIRWAY.

SELF-LUMINOUS.

SMOKE-PROTECTED ASSEMBLY SEATING.

STAIR.

STAIRWAY.

STAIRWAY, SPIRAL.

WINDER.

The following terms shall, for the purposes of this chapter, have the meanings shown herein:

COLLECTING SAFE AREA. A safe area that receives occupants from the assembly space it serves, as well as from other safe areas.

OPEN EXTERIOR SPACE. A street or other public space; or a yard, court, or plaza open on one or more sides and unroofed or open on all sides, which provides egress to a street or public space.

SAFE AREA. An interior or exterior space that serves as a means of egress by providing a transitional area from, and that also serves as a normal means of entry to, an assembly space.

SEATING SECTION. An area of seating bounded on all sides by aisles, cross aisles, walls or partitions.

Protruding objects are permitted to extend below the minimum ceiling height required by Section 1003.2 where a minimum headroom of 84 inches (2133.6 mm) is provided over any walking surface, including walks, corridors, aisles and passageways. Not more than 50 percent of the ceiling area of a means of egress shall be reduced in height by protruding objects.
A barrier shall be provided where the vertical clearance is less than 80 inches (2032 mm) high. The leading edge of such a barrier shall be located 27 inches (685 mm) maximum above the floor.

A free-standing object mounted on a post or pylon shall not overhang that post or pylon more than 4 inches (101.6 mm) where the lowest point of the leading edge is more than 27 inches (685 mm) and less than 80 inches (2032 mm) above the walking surface. Where a sign or other obstruction is mounted between posts or pylons and the clear distance between the posts or pylons is greater than 12 inches (304.8 mm), the lowest edge of such sign or obstruction shall be 27 inches (685 mm) maximum or 80 inches (2032 mm) minimum above the finished floor or ground.

Objects with leading edges more than 27 inches (685 mm) and not more than 80 inches (2030 mm) above the floor shall not project horizontally more than 4 inches (101.6 mm) into the circulation path.

Protruding objects shall not reduce the minimum clear width of accessible routes.

Cumulative occupant loads shall be determined in accordance with Sections 1004.1.1.1 and 1004.1.1.2.

Where an area under consideration contains multiple functions having different occupant load factors, the design occupant load for such area shall be based on the floor area of each function calculated independently.

The number of occupants shall be computed at the rate of one occupant per unit of area as prescribed in Table 1004.1.3. For areas without fixed seating, the occupant load shall be not less than that number determined by dividing the floor area under consideration by the occupant load factor assigned to the function of the space as set forth in Table 1004.1.3.

TABLE 1004.1.3
MAXIMUM FLOOR AREA ALLOWANCES PER OCCUPANT

FUNCTION OF SPACE	OCCUPANT LOAD FACTORa
Accessory storage areas, mechanical equipment room	300 gross
Agricultural building	300 gross
Aircraft hangars	500 gross
Assembly
Gaming floors (keno, slots, etc.)	11 gross
Exhibit gallery and museum	30 net
Assembly with fixed seats	See Section 1004.3
Assembly without fixed seats
Concentrated (chairs only — not fixed)	7 net
Dance floor	5 net
Dance floor (ballroom)	10 net
Standing space	5 net
Unconcentrated (tables and chairs)	15 net
Bowling centers, allow 5 persons for each lane including 15 feet of runway, and for additional areas	7 net
Business areas, including accessory areas on terraces and rooftops	100 grossb,d
Courtrooms — other than fixed seating areas	40 net
Day Care:
Age under 6 months	50 net
Age 6 months — 2 years	40 net
Age 2 years — 6 years	30 net
Age above 6 years	50 net
Dormitories	50 gross
Educational
Classroom area	20 net
Shops and other vocational room areas	50 net
Kindergarten, and pre-kindergarten	30 net
Exercise rooms	50 gross
Gymnasiums	15 net
Group H-5 Fabrication and manufacturing areas	200 gross
Industrial areas	100 gross
Institutional areas
Inpatient treatment areas	240 gross
Outpatient areas	100 gross
Sleeping areas	120 gross
Kitchens, commercial	200 gross
Library
Reading rooms	50 net
Stack area	100 gross
Locker rooms	50 gross
Mall buildings — covered and open	See Section 402.8.2
Mercantile
Areas on other floors	60 gross
Basement and grade floor areas	30 gross
Storage, stock, shipping areas	300 gross
Parking garages	200 gross
Passenger terminal
Baggage claim	20 gross
Baggage handling	300 gross
Concourse	100 gross
Passenger terminal or platform	1.5 X C*
Waiting area (Standing)	15 gross
Waiting areas (Seated)	5 net
Residential
Within dwelling units	200 gross
Rooftop and terrace accessory to Groups R-2 and R-3	200 grossb,c,d
Indoor residential amenity spaces accessory to Group R-2 (concentrated)e	15 net
Indoor residential amenity spaces accessory to Group R-2 (unconcentrated)e	50 net
Skating rinks, swimming pools
Rink and pool	50 gross
Decks	15 gross
Stages and platforms	15 net for performing area and 50 net remaining area
Warehouses	500 gross

1. Floor area in square feet per occupant.
2. For the purposes of occupant load calculation, permanent fixtures and amenities such as shrubs, decorative pools, non-walkable paving surfaces, etc. may be deducted from the total floor area.
3. A rooftop or terrace in Group R-2 or R-3 occupancies that is provided for the incidental, recreational use by the residential tenants residing in the same residential building.
4. Where the maximum occupant load of the rooftop or terrace exceeds 74 persons based on occupant load calculations, a Place of Assembly Certificate of Operation is required pursuant to Section 28-117.1 of the Administrative Code and Item 1 of Section 303.7 of this code.
5. To be used only when the occupant load for the function of the space is not listed elsewhere in Table 1004.1.3.

The capacity, in inches, of means of egress stairways shall be calculated by multiplying the occupant load served by such stairways by a means of egress capacity factor of 0.3 inch (7.6 mm) per occupant. Where stairways serve more than one story, only the occupant load of each story considered individually shall be used in calculating the required capacity of the stairways serving that story.

The capacity, in inches, of means of egress components other than stairways shall be calculated by multiplying the occupant load served by such component by a means of egress capacity factor of 0.2 inch (5.1 mm) per occupant.

Doors, when fully opened, shall not reduce the required width by more than 7 inches (177.8 mm). Doors in any position shall not reduce the required width by more than one-half.

Handrail projections shall be in accordance with the provisions of Section 1014.8. Other nonstructural projections such as trim and similar decorative features shall be permitted to project into the required width not more than 1¹/₂ inches (38.1 mm) on each side.

Protruding objects shall comply with the applicable requirements of Section 1003.3.

Two exits or exit access doorways from any space shall be provided where the design occupant load or the common path of egress travel distance exceeds the values listed in Table 1006.2.1.

TABLE 1006.2.1
SPACES WITH ONE EXIT OR EXIT ACCESS DOORWAY

OCCUPANCY	MAXIMUM OCCUPANT LOAD OF SPACE	MAXIMUM COMMON PATH OF EGRESS TRAVEL DISTANCE (feet)
		Without Sprinkler System (feet)		With Sprinkler System (feet)
		Occupant Load
		OL ≤ 30	OL > 30
Ac, Ef, M	74	75	75	75a
B	74	100	75	100a
F	49	75	75	100a
H-1, H-2, H-3	3	NP	NP	25b
H-4b, H-5b, I-1, I-3, I-4	10	NP	NP	75a
I-2d	See Section 407	NP	NP	75a
R-1	20	NP	NP	75a
R-2	20g	NP	NP	125a
S	29	100	75e	100a
U	74	100	75	75a

The numbers of exits or access to exits shall be provided in the uses described in Sections 1006.2.2.1 through 1006.2.2.5.

Each story or occupied roof designed for human occupancy or use shall have the minimum number of exits, or access to exits, as specified in Table 1006.3.1. A single exit or access to a single exit shall be permitted in accordance with Section 1006.3.2. The required number of exits, or exit access stairways or ramps providing access to exits, from any such story or occupied roof shall be maintained until arrival at the exit discharge or a public way.

TABLE 1006.3.1
MINIMUM NUMBER OF EXITS OR ACCESS TO EXITS PER STORY

OCCUPANT LOAD (persons per story)	MINIMUM NUMBER OF EXITS (per story)
1-500	2
501-1,000	3
More than 1,000	4

A single exit or access to a single exit shall be permitted from any story or occupied roof designed for human occupancy or use where one of the following conditions exists:

1. The occupant load, number of dwelling units and exit access travel distance do not exceed the values in Table 1006.3.2.
2. Rooms, areas and spaces complying with Section 1006.2.1 with exits that discharge directly to the exterior at the level of exit discharge are permitted to have one exit or access to a single exit.
3. Open or enclosed parking garages where vehicles are mechanically parked shall be permitted to have one exit provided such exit shall not be a vehicle ramp.
4. Group R-3 occupancies shall be permitted to have one exit or access to a single exit.
5. Individual single-story or multistory dwelling units shall be permitted to have a single exit or access to a single exit from the dwelling unit provided that both of the following criteria are met:
   1. The dwelling unit complies with Section 1006.2.1 as a space with one means of egress.
   2. Either the exit from the dwelling unit discharges directly to the exterior at the level of exit discharge, or the exit access outside the dwelling unit's entrance door provides access to not less than two approved independent exits.
6. Buildings of Occupancy Group R-2 where all of the following conditions are met:
   1. The building does not exceed four stories;
   2. The building contains not more than three dwelling units per story;
   3. The building is of construction Type I or II;
   4. The building does not exceed 2,500 square feet (232.3 m²) per story;
   5. Each dwelling unit has at least one window facing the street, or facing a lawful yard with open, unobstructed, and direct access to the street. Such yard or direct access shall be a minimum width equal to 25 percent of the vertical distance from the windowsill of the highest operable window, facing such yard or direct access, to the grade of such yard or direct access directly below such window, but shall in no case be less than 36 inches (914.4 mm) wide;
   6. The stairway extends to the roof surface through a stairway bulkhead complying with Section 1509.2, provided the roof has a slope not steeper than 20 degrees (0.35 rad), or the stairway is constructed against the street wall, with one window facing the street at each landing and access to the roof is provided via a scuttle with a stationary, noncombustible access ladder;
   7. The stairway is enclosed in 2-hour fire-rated walls with all exit doors leading into the stairway having at least 1¹/₂-hour fire rating; and
   8. The building is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.2.
7. Buildings of Occupancy Group R-2 of construction Type I or II not exceeding six stories and not exceeding 2,000 square feet (185.8 m²) per story.

TABLE 1006.3.2
STORIES WITH ONE EXIT OR ACCESS TO ONE EXIT

STORY	OCCUPANCY	MAXIMUM OCCUPANT LOAD PER FLOOR	MAXIMUM TRAVEL DISTANCE (feet)
First story above grade plane or cellarf	A, Bb, Ec, Fb, M, U, Sb	49	75
	H-2, H-3	3	25
	H-4, H-5, I, Re	10	75
	Sa	29	100
Second story above grade plane	B, F, M, Sa	29	75
	R-2d,e	NA	50
Third story above grade plane	R-2d,e	NA	50

Where two exits, exit access doorways, exit access stairways or ramps, or any combination thereof, are required from any portion of the exit access, they shall be placed a distance apart equal to not less than one-half of the length of the maximum overall diagonal dimension of the building or area to be served measured in a straight line between them. Stairs sharing any common wall, floor, ceiling, scissor stair assembly, or other enclosure shall be counted as one exit stairway.

Where access to three or more exits is required, not less than two exit or exit access doorways shall be arranged in accordance with the provisions of Section 1007.1.1. Additional required exit or exit access doorways shall be arranged a reasonable distance apart so that if one becomes blocked, the others will be available.

Where two exit access stairways or ramps provide the required means of egress to exits at another story, the required separation distance shall be maintained for all portions of such exit access stairways or ramps.

The means of egress illumination level shall be not less than 1 footcandle (11 lux) at the walking surface.

In Group I-2 occupancies where two or more exits are required, on the exterior landings required by Section 1010.1.6, means of egress illumination levels for the exit discharge shall be provided such that failure of any single lighting unit shall not reduce the illumination level on that landing to less than 1 footcandle (11 lux).

Automatic, occupant sensor or photosensor lighting controls shall be permitted within means of egress, provided that the illumination level is not reduced to a level below the minimum requirements of Section 1008.2.1, and the switch controllers are equipped for fail-safe operation ensuring that if the sensor or control fails, the lighting levels will be at the levels required by Section 1008.2.1.

In the event of power supply failure in rooms and spaces that require two or more means of egress, an emergency electrical system shall automatically illuminate all of the following areas:

1. Aisles.
2. Corridors.
3. Exit access stairways and ramps.
4. Safe areas in assembly occupancies where required by Section 1029.19.3.2.

In the event of power supply failure in buildings that require two or more means of egress, an emergency electrical system shall automatically illuminate all of the following areas:

1. Interior exit access stairways and ramps.
2. Interior and exterior exit stairways and ramps.
3. Exit passageways.
4. Vestibules and areas on the level of discharge used for exit discharge in accordance with Section 1028.1.
5. Exterior landings as required by Section 1010.1.6 for exit doorways that lead directly to the exit discharge.

In the event of power supply failure, an emergency electrical system shall automatically illuminate all of the following areas:

1. Electrical equipment rooms containing electrical point of entry or building service disconnect.
2. Fire command centers.
3. Fire pump rooms.
4. Generator rooms.
5. Public restrooms with an area greater than 300 square feet (27.8 m²).

The emergency power system shall provide power for a duration of not less than 90 minutes and shall consist of storage batteries, unit equipment or an on-site generator. The installation of the emergency power system shall be in accordance with Section 2702.

Emergency lighting facilities shall be arranged to provide initial illumination that is not less than an average of 1 footcandle (11 lux) and a minimum at any point of 0.1 footcandle (1 lux) measured along the path of egress at floor level. Illumination levels shall be permitted to decline to 0.6 footcandle (6 lux) average and a minimum at any point of 0.06 footcandle (0.6 lux) at the end of the emergency lighting time duration. A maximum-to-minimum illumination uniformity ratio of 40 to 1 shall not be exceeded. In buildings that contain existing photoluminescent exit path markings tested in laboratory conditions with greater than 1 footcandle (11 lux) of activating, the initial illumination shall not be less than that required for activating the approved photoluminescent illumination. In Group I-2 occupancies, failure of any single lighting unit shall not reduce the illumination level to less than 0.2 footcandle (2.2 lux).

In high-rise buildings subject to Section 403, at least one required accessible means of egress shall be an elevator complying with Section 1009.4.

Where an exit discharge is not accessible, an exterior area for assisted rescue shall be provided in accordance with Section 1009.7. An exterior area for assisted rescue shall not be required where an exit discharge is on an assisted rescue path from a stairway or an elevator.

Where an exit stairway is open to the exterior, the accessible means of egress shall include either an area of rescue assistance in accordance with Section 1009.6 or an exterior area for assisted rescue in accordance with Section 1009.7.

Platform lifts on an accessible means of egress shall not be installed in a fully enclosed hoistway.

The maximum travel distance from any accessible space to an area of rescue assistance shall not exceed the exit access travel distance permitted for the occupancy in accordance with Section 1017.1.

Every required area of rescue assistance shall have direct access to a stairway complying with Sections 1009.3 and 1023, or an elevator complying with Section 1009.4.

Each area of rescue assistance shall be sized to accommodate one wheelchair space of 30 inches by 48 inches (762 mm by 1220 mm) for each 200 occupants or portion thereof, based on the occupant load of the area of rescue assistance and areas served by the area of rescue assistance. Such wheelchair spaces shall not reduce the means of egress minimum width or required capacity. Access to any of the required wheelchair spaces in an area of rescue assistance shall not be obstructed by more than one adjoining wheelchair space.

Each area of rescue assistance shall be separated from the remainder of the story by a smoke barrier complying with Section 709 or a horizontal exit complying with Section 1026. Each area of rescue assistance shall be designed to minimize the intrusion of smoke.

Areas of rescue assistance shall be provided with a two-way communication system complying with Sections 1009.8.1 and 1009.8.2.

Each exterior area for assisted rescue shall be sized to accommodate wheelchair spaces in accordance with Section 1009.6.3.

Exterior walls separating the exterior area of assisted rescue from the interior of the building shall have a minimum fire-resistance rating of 1 hour, rated for exposure to fire from the inside. The fire-resistance-rated exterior wall construction shall extend horizontally 10 feet (3048 mm) beyond the landing on either side of the landing or equivalent fire-resistance-rated construction is permitted to extend out perpendicular to the exterior wall 4 feet (1220 mm) minimum on the side of the landing. The fire-resistance-rated construction shall extend vertically from the ground to a point 10 feet (3048 mm) above the floor level of the area for assisted rescue or to the roof line, whichever is lower. Openings within such fire-resistance-rated exterior walls shall be protected in accordance with Section 716.

The exterior area for assisted rescue shall be open to the outside air. The sides other than the separation walls shall be not less than 50 percent open, and the open area shall be distributed so as to minimize the accumulation of smoke or toxic gases.

Stairways that are part of the accessible means of egress for the exterior area for assisted rescue shall provide a clear width of 48 inches (1220 mm) between handrails.

Two-way communication systems shall provide communication between each required location and the fire command center or a central control point location approved by the Fire Department. Where the central control point is not a constantly attended location, a two-way communication system shall have a timed automatic telephone dial-out capability to a monitoring location or 911. The two-way communication system shall include both audible and visible signals.

Directions for the use of the two-way communication system, instructions for summoning assistance via the two-way communication system and written identification of the location shall be posted adjacent to the two-way communication system. Signage shall comply with the ICC A117.1 requirements for visual characters.

The minimum width and height of each door opening shall be in accordance with this section.

Egress doors shall be installed in accordance with this section.

The force for pushing or pulling open interior swinging egress doors, other than fire doors, shall not exceed 5-pounds (22.2 N). These forces do not apply to the force required to retract latch bolts or disengage other devices that hold the door in a closed position. For other swinging doors, as well as sliding and folding doors, the door latch shall release when subjected to a 15-pound (66.7 N) force. The door shall be set in motion when subjected to a 30-pound (133.4 N) force. The door shall swing to a full-open position when subjected to a 15-pound (66.7 N) force.

Special doors and security grilles shall comply with the requirements of Sections 1010.1.4.1 through 1010.1.4.4.

There shall be a floor or landing on each side of a door. Such floor or landing shall be at the same elevation on each side of the door. Landings shall be level except for exterior landings, which are permitted to have a slope not to exceed 0.25 unit vertical in 12 units horizontal (2-percent slope).

Landings shall have a width not less than the width of the stairway or the door, whichever is greater. Doors in the fully open position shall not reduce a required dimension by more than 7 inches (177.8 mm). At any stairway landing, or when a door landing serves an occupant load of 50 or more, doors in any position shall not reduce the landing to less than 75 percent of its required width. Landings shall have a length measured in the direction of travel of not less than 44 inches (1117.6 mm).

Thresholds at doorways shall not exceed ³/₄ inch (19.1 mm) in height above the finished floor or landing for sliding doors serving dwelling units or ¹/₂ inch (12.7 mm) above the finished floor or landing for other doors. Raised thresholds and floor level changes greater than ¹/₄ inch (6.4 mm) at doorways shall be beveled with a slope not greater than one unit vertical in two units horizontal (50-percent slope).

Space between two doors in a series shall be 48 inches (1220 mm) minimum plus the width of a door swinging into the space. Doors in series shall swing either in the same direction or away from the space between the doors.

Except as specifically permitted by this section, egress doors shall be readily openable from the egress side without the use of a key or special knowledge or effort.

Doors serving the following shall not be provided with a latch or lock other than panic hardware or fire exit hardware:

1. Group H occupancies;
2. A room or space with an occupant load of 75 or more in a Group A or E occupancy;
3. A building or nonaccessory tenant space used for assembly purposes that is permitted to be classified as a Group B occupancy pursuant to Section 303.1.2; and
4. An accessory room or space used for assembly purposes where permitted to be classified as a Group B occupancy or as part of the occupancy it is accessory to, pursuant to Section 303.1.3.

Panic hardware is not required on gates surrounding stadiums where such gates are under constant immediate supervision while the public is present, and where safe dispersal areas based on 3 square feet (0.28 m²) per occupant are located between the fence and enclosed space. Such required safe dispersal areas shall not be located less than 50 feet (15 240 mm) from the enclosed space. See Section 1028.5 for means of egress from safe dispersal areas.

Turnstiles more than 39 inches (990.6 mm) high shall meet the requirements for revolving doors.

Where serving an occupant load greater than 300, each manually-operated turnstile and automatic turnstile that is not portable shall have a side-hinged swinging door that conforms to Section 1010.1 within 50 feet (15 240 mm).

Building entrance doors and other exterior exit doors shall be equipped with heavy duty lock sets with auxiliary latch bolts to prevent the latch from being manipulated by means other than a key. Latch sets shall have stop-work in the inside cylinder controlled by a master key only. Outside cylinders of main entrance door locks shall be operated by the tenants' key, which shall not be keyed to also open the tenants' apartment door. A light or lights shall be provided at or near the outside of the front entranceway of the building providing not less than 5-footcandles (53.82 lux) intensity measured at the floor level for the full width of the entranceway.

Doors to dwelling units shall be equipped with a heavy duty latch set and a heavy duty dead bolt operable by a key from the outside and a thumb-turn from the inside. Those doors shall also be equipped with a chain guard so as to permit partial opening of the door. Dwelling unit entrance doors shall also be equipped with a viewing device located so as to enable a person on the inside of the entrance door to view a person immediately outside.

All openable windows shall be equipped with sash locks designed to be openable from the inside only. Grilles lockable from the inside only may be placed on the inside or outside of windows that are accessible from grade but that do not serve to provide access to exits.

Buildings containing eight or more dwelling units shall be provided with an intercommunication system located at the door giving access to the main entrance lobby, consisting of a device or devices for voice communication between the occupant of each dwelling unit and a person outside the door to the main entrance lobby, and permitting such dwelling unit occupant to release the locking mechanism of said door from the dwelling unit. In buildings provided with a full-time lobby attendant, the intercommunication system may be between each dwelling unit and the attendant's station.

For the purpose of this section, all dimensions are exclusive of carpets, rugs or runners.

Stair riser heights shall be 7 inches (177.8 mm) maximum and 4 inches (101.6 mm) minimum. The riser height shall be measured vertically between the nosings of adjacent treads. Rectangular tread depths shall be 11 inches (279.4 mm) minimum measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's nosing. The greatest tread depth within any flight of stairs shall not exceed the smallest by more than ³/₈ inch (9.5 mm). Winder treads shall have a minimum tread depth of 11 inches (279.4 mm) between the vertical planes of the foremost projection of adjacent treads at the intersections with the walkline and a minimum tread depth of 10 inches (254 mm) within the clear width of the stair.

Winder treads are not permitted in means of egress stairways except within a dwelling unit.

Stair treads and risers shall be of uniform size and shape. The tolerance between the largest and smallest riser height or between the largest and smallest tread depth shall not exceed ³/₈ inch (9.5 mm) in any flight of stairs. The greatest winder tread depth at the walkline within any flight of stairs shall not exceed the smallest by more than ³/₈ inch (9.5 mm).

Nosings shall have a curvature or bevel of not less than ¹/₁₆ inch (1.6 mm) but not more than ⁹/₁₆ inch (14.3 mm) from the foremost projection of the tread. Risers shall be solid and vertical or sloped under the tread above from the underside of the nosing above at an angle not more than 30 degrees (0.52 rad) from the vertical.

The walking surface of treads and landings of a stairway shall not be sloped steeper than one unit vertical in 48 units horizontal (2-percent slope) in any direction. Stairway treads and landings shall have a solid surface. Finish floor surfaces shall be securely attached.

Outdoor stairways and outdoor approaches to stairways shall be designed so that water will not accumulate on walking surfaces. In occupancies other than Group R-3 and occupancies in Group U that are accessory to an occupancy in Group R-3, treads, platforms and landings that are part of exterior stairways in climates subject to snow or ice shall be protected to prevent the accumulation of same.

The walls and soffits within enclosed usable spaces under enclosed and unenclosed stairways shall be protected by 1-hour fire-resistance-rated construction or the fire-resistance rating of the stairway enclosure, whichever is greater. Access to the enclosed space shall not be directly from within the stairway enclosure.

There shall not be enclosed usable space under exterior exit stairways unless the space is completely enclosed in 1-hour fire-resistance-rated construction. The open space under exterior stairways shall not be used for any purpose.

In buildings in Occupancy Groups I-1, R- 1 and R-2 two stories or more in height, with roofs having a slope of 15 degrees (0.26 rad) or less, all interior exit stairways, except those terminating at the level of a setback roof, shall extend to the roof surface.

Roofs and penthouses containing elevator equipment that must be accessed for maintenance are required to be accessed by a stairway.

Handrails shall be provided on both sides of alternating tread devices and shall comply with Section 1014.

Alternating tread devices shall have a minimum tread depth of 5 inches (127 mm), a minimum projected tread depth of 8¹/₂ inches (215.9 mm), a minimum tread width of 7 inches (177.8 mm) and a maximum riser height of 9¹/₂ inches (241.3 mm). The tread depth shall be measured horizontally between the vertical planes of the foremost projections of adjacent treads. The riser height shall be measured vertically between the leading edges of adjacent treads. The riser height and tread depth provided shall result in an angle of ascent from the horizontal of between 50 and 70 degrees (0.87 and 1.22 rad). The initial tread of the device shall begin at the same elevation as the platform, landing or floor surface.

Handrails shall be provided on both sides of ships ladders.

Ships ladders shall have a minimum tread depth of 5 inches (127 mm). The tread shall be projected such that the total of the tread depth plus the nosing projection is not less than 8¹/₂ inches (215.9 mm). The maximum riser height shall be 9¹/₂ inches (241.3 mm).

The minimum width and required capacity of a means of egress ramp shall be not less than that required for corridors by Section 1020.2. The clear width of a ramp between handrails, if provided, or other permissible projections shall be 36 inches (914.4 mm) minimum.

The minimum headroom in all parts of the means of egress ramp shall be not less than 84 inches (2133.6 mm).

Means of egress ramps shall not reduce in width in the direction of egress travel. Projections into the required ramp and landing width are prohibited. Doors opening onto a landing shall not reduce the clear width to less than 42 inches (1066.8 mm).

Landings shall have a slope not steeper than one unit vertical in 48 units horizontal (2-percent slope) in any direction. Changes in level are not permitted.

The landing width shall be not less than the width of the widest ramp run adjoining the landing.

The landing length shall be 60 inches (1525 mm) minimum.

Where changes in direction of travel occur at landings provided between ramp runs, the landing shall be 60 inches by 60 inches (1524 mm by 1524 mm) minimum.

Where doorways are located adjacent to a ramp landing, maneuvering clearances required by ICC A117.1 are permitted to overlap the required landing area.

The surface of ramps shall be of slip-resistant materials that are securely attached.

Outdoor ramps and outdoor approaches to ramps shall be designed so that water will not accumulate on walking surfaces. In other than occupancies in Group R-3, and occupancies in Group U that are accessory to an occupancy in Group R-3, surfaces and landings which are part of exterior exit ramps in climates subject to snow or ice shall be designed to minimize the accumulation of same.

A curb, rail, wall or barrier serving as edge protection shall be provided as follows:

1. Solid barriers. Solid barriers shall extend at least 4 inches (101.6 mm) from the floor or ground surface.
2. Other types of barriers. Other types of barriers shall prevent the passage of a 4-inch (101.6 mm) diameter sphere, where any portion of the sphere is within 4 inches (101.6 mm) of the floor or ground surface.

In high-rise buildings subject to Section 403, exit signs shall be placed within exits at horizontal extensions to indicate the transition from vertical to horizontal direction an at turns along the horizontal path.

The height of letters shall be not less than 6 inches (152.4 mm), except that in Group A and Group R-1 occupancies letters shall be not less than 8 inches (203.2 mm) high. Graphics shall have letter widths, strokes and spacing in proportion to their height.

Every exit sign and directional exit sign shall have plainly legible letters not less than 6 inches (152.4 mm) high with the principal strokes of the letters not less than ³/₄ inch (19.1 mm) wide. The word "EXIT" shall have letters having a width not less than 2 inches (50.8 mm) wide, except the letter "I," and the minimum spacing between letters shall be not less than ³/₈ inch (9.5 mm). In Group A and R-1 occupancies letters shall be not less than 8 inches (203.2 mm) high. Signs larger than the minimum established in this section shall have letter widths, strokes and spacing in proportion to their height.

The word "EXIT" shall be in high contrast with the background and shall be clearly discernible when the means of exit sign illumination is or is not energized. The letters of exit signs shall be red. If a chevron directional indicator is provided as part of the exit sign, the construction shall be such that the direction of the chevron directional indicator cannot be readily changed.

The face of an exit sign illuminated from an external source shall have an intensity of not less than 25 footcandles (269.1 lux).

Exit signs shall be illuminated at all times. To ensure continued illumination for a duration of not less than 90 minutes in case of primary power loss, the sign illumination means shall be connected to an emergency power system provided from storage batteries, unit equipment or an on-site generator. The installation of the emergency power system shall be in accordance with Chapter 27.

Handrails with a circular cross section shall have an outside diameter of not less than 1¹/₄ inches (31.75 mm) and not greater than 2 inches (50.8 mm). Where the handrail is not circular, it shall have a perimeter dimension of not less than 4 inches (101.6 mm) and not greater than 6¹/₄ inches (158.75 mm) with a maximum cross-sectional dimension of 2¹/₄ inches (57.15 mm) and minimum cross-sectional dimension of 1 inch (25.4 mm). Edges shall have a minimum radius of 0.01 inch (0.25 mm).

Handrails with a perimeter greater than 6¹/₄ inches (158.75 mm) shall provide a graspable finger recess area on both sides of the profile. The finger recess shall begin within a distance of ³/₄ inch (19 mm) measured vertically from the tallest portion of the profile and achieve a depth of not less than ⁵/₁₆ inch (7.9 mm) within ⁷/₈ inch (22 mm) below the widest portion of the profile. This required depth shall continue for not less than ³/₈ inch (9.6 mm) to a level that is not less than 1³/₄ inches (44.5 mm) below the tallest portion of the profile. The width of the handrail above the recess shall be not less than 1¹/₄ inches (31.75 mm) to not greater than of 2³/₄ inches (69.9 mm). Edges shall have a minimum radius of 0.01 inch (0.25 mm).