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Greater Bengaluru City Corporation -

Section 21 in Bangalore Mahanagara Palike Building Bye-laws 2003

21. Exit requirements for high rise buildings, public and industrial buildings

21.1General
21.1.1Every building meant for human occupancy shall be provided with exits sufficient to permit safe escape of occupants, in case of fire or other emergency.
21.1.2In every building for multi family dwellings and all places of assembly, exits shall comply with the minimum requirements of these bye-laws.
21.1.3All exits shall be free of obstructions.
21.1.4No building shall be altered so as to reduce the number, and size of exits to less than that required.
21.1.5Exits shall be clearly visible Routes to reach the exits shall be clearly marked and signs posted so as to guide the persons using each floor.
21.1.6Wherever necessary, adequate and continuous illumination shall be provided for exits.
21.1.7Fire fighting equipment shall be suitably located and clearly marked.
21.1.8Alarm devices shall be installed to ensure prompt evacuation of the persons concerned.
21.1.9All exits shall provide continuous means of egress to the exterior of buildings or to the exterior open space leading to a street.
21.1.10Exits shall be so arranged that they may be reached without passing through another occupied unit.
21.2Arrangement of exits – Exits shall be so located that the travel distance on the floor shall not exceed the limits given in Table 14.
21.3Capacity of exits
(i)The unit of exit width used to measure capacity of any exist shall be 50 cm. A clear width of 25 cm. shall be counted as an additional half unit. Clear width less than 25 cm shall not be counted for exit width;
(ii)The occupants per unit exit width shall be as given in Table 15.
21.4Occupant load –The occupant load of buildings shall be worked out as given in Table 16.
21.5Number of exits -
(i)The location, width and number of exits shall be in accordance with the travel distance, capacity of exits and the population of building based on occupant load;
(ii)There shall not be less than 2 exits serving every floor for buildings of 15 mtrs height and above and at least one of them shall be an internal stairway.
TABLE 14(Bye-law 21.2)TRAVEL DISTANCE FOR OCCUPANTS
Sl. No. Group of occupancy Maximum travel distance in mtrs.
1. Residential 22.5
2. Educational 22.5
3. Institutional 22.5
4. Assembly 30.0
5. Business 45.0
6. Commercial 30.0
7. Industrial 30.0
8. Storage 30.0
9. Hazardous 22.5
Note: (1) The travel distance to any exit from the dead end of a corridor shall not exceed half the distance specified above except in educational, assembly and institutional occupancies in which case it shall not exceed 6 m.Note (2) Whenever more than one exit is required for any room, space or floor of a building, exits shall be placed as remote from each other as possible and shall be arranged so as to provide direct access to the exits from different directions.TABLE 15(Bye-law 21.3)OCCUPANTS PER UNIT EXIT WIDTH – MAXIMUM NUMBER OF OCCUPANTS
Sl.No. Group of occupancy Stairways Ramps Doors
1. Residential 25 50 75
2. Educational 25 50 75
3. Institutional 25 50 75
4. Assembly 40 50 60
5. Business 50 60 75
6. Commercial 50 60 75
7. Industrial 50 60 75
8. Storage 50 - 75
9. Hazardous 25 30 40
Note: Horizontal allowance: When horizontal exit is provided in buildings of mercantile, storage,industrial, business and assembly occupancies, the capacity per storey per unit width ofexit stairways in the table above, may be increased by 50 % and in the buildings ofindustrial occupancy, it may be increased by 100%.TABLE 16(Bye-law 21.4)OCCUPANT LOAD
Sl. No. Group of Occupancy Occupant load-gross floor area in sq. mtrs per person
1. Residential 12.5
2. Educational 4.0
3. Institutional 15.0*
4. Assembly  
  a) With fixed or loose seats and dance floors 0.6**
  b) Without seating facilities including dining rooms 1.5**
5. Business and industrial 10.0
6. Storage 30.0
7. Hazardous 10.0
* The gross area shall mean plinth area or covered area. Occupant load in dormitory portions or homes for the aged, orphanages, asylums, etc., where sleeping accommodation is provided, shall be calculated at not less than 7.5 sqm. gross floor area per person.** The gross floor area shall include, in addition, the main assembly room or space, any occupied connecting room or space in the same storey or in the storeys above or below where entrance is common to such rooms and spaces and they are available for use by the occupants or the assembly place. No deduction shall be made in the gross floor area for corridors, closets or other sub-divisions. The areas shall include all space serving the particular assembly occupancy.Note: The occupant load of a mezzanine floor discharging to a floor below shall be added to that floor occupancy and the capacity of the exits shall be designed for the total occupancy load thus established.
21.6Doorways -
(a)Every exit doorway shall open into an enclosed stairway, a horizontal exit, or a corridor or passageway providing continuous and protected means of egress;
(b)No exit doorway shall be less than 75 cm in width in the case of residential buildings and 100 cm in the case of other buildings. Doorways shall be not less than 200 cm. in height.
(c)Exit doorways shall open outwards i.e., away from the room. But shall not obstruct the travel along any exit. No door, when open, shall reduce the required width of stairway or landing to less than 90 cm. Overhead or sliding doors shall not be installed;
(d)Exit doors shall not open immediately upon a flight of stairs; a landing equal to atleast the width of the door shall be provided in the stairway at each doorway; level of landing shall be same as that of the floor which it serves.
21.7Revolving doors -
(a)Revolving doors shall not be used as required exits except in residential, business and commercial occupancies, but shall not constitute more than 1/2 the total required door width;
(b)When revolving doors are considered as required exitway, the following assumptions shall be made.
(1)Each revolving door shall be counted as one half of the exit unit width.
(2)Revolving doors shall not be located at the foot of a stairway. Any stairway servedby a revolving door shall discharge through a lobby or foyer.
21.8Staircase -
(a)Interior stairs shall be constructed of non-combustive materials;
(b)Interior staircases of all buildings with the exception of residential buildings upto GF+3 floors shall be constructed as self contained units with atleast one side adjacent to an external wall. The staircase shall be completely enclosed in the case of buildings of 15 meters height and above;
(c)A staircase shall not be arranged around a lift shaft unless the latter is entirely enclosed by a material of fire resistance rating;
(d)Hollow combustible construction shall not be permitted;
(e)The minimum width of an internal staircase shall be as per bye-law 20.6;
(f)The minimum width of treads without nosing shall be as per bye-law 20.6;
(g)The maximum riser shall be as per bye-law 20.6;
(h)Handrails shall be provided with a minimum height pf 100 cm. for all buildings and shall be firmly supported;
(i)No windings should be provided in a public building except in the case of emergency exits.
21.9Fire escapes or external stairs -
(a)Fire escapes shall not be taken into account in calculating the evacuation time of a building;
(b)All fire escapes above ground level shall be directly connected to the ground and shall not lead to the basement floor;
(c)All entrances to a fire escape shall be separate and remote from the internal staircase;
(d)The route to fire escape shall be free of obstruction at all times except a door way
leading to the fire escape which shall have the required fire resistance;
(e)Fire escapes shall be constructed of non-combustible materials;
(f)Stairs of fire escapes shall have straight flights not less than 75 cm. wide, 20 cm. tread and with risers not more than 19 cm. The number of risers shall be limited to 16 per flight;
(g)Handrails shall be of a height of not less than 100 cm.
21.10Spiral stairs (fire escape) –The use of spiral staircases shall be limited to low occupant loads and to buildings of not more than 9 metres height, unless they are connected to platforms such as balconies and terraces to provide for a pause during escape. A spiral fire escape shall be not less than 150 cm in diameter and shall be designed to give adequate headroom;
21.11Ramps –Ramps with a slope of not more than 1:10 may be substituted and shall comply with all the applicable requirements of required stairways regarding enclosures, capacity and dimensions. Larger slopes shall be provided for special uses but in no case greater than 1 in 10. For all slopes exceeding, 1:10 and wherever the use is such as to involve danger of slipping, the ramp shall be surfaced with approved non-slipping materials;
21.12Exit corridors and passage ways - Exit corridors and passage ways shall be of width of not less than twice the aggregate required width of exit doorways leading from them in the direction of travel to the exits. Where stairways discharge through corridors and passage ways, the height of corridors and passage ways shall be not less than 2.4 mtrs.