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Legend: Explanations & Illustrations Rationale Note Revision history Print

Clause 2.2 - DETERMINATION OF EXIT REQUIREMENTS

2.2.1 General

R Rationale - Clause 2.2.1

The exit provisions allow occupants to leave the fire area safely in the shortest possible time to a safe area.

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The determination of exit requirements for a building shall be based upon the type of use or occupancy of the building, the occupant load, the floor area, the travel distance to an exit and the capacity of exits as provided in Table 2.2A and herein. Every storey of a building shall be provided with exit facilities for its occupant load. Vertical exits provided from any storey above ground level may serve simultaneously all storeys above the ground level. Vertical exits provided from any storey below ground level may serve all storeys below ground level, subject to the provisions of Cl.2.3.5 which prohibit basement staircases being continuous with exit staircases serving the upper storeys, unless otherwise allowed by the SCDF.

2.2.2  Mixed occupancy

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Where different parts of a building or storey of a building are designed for different types of occupancies or used for different purposes at the same time, the exit requirements of the entire building or storey of the building shall be determined on the basis of that type of occupancy or usage having the strictest exit requirements or the exit requirements for each building section shall be determined separately.

2.2.3 Multiple occupancy or use

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Where a building or storey of a building or a part of a building is used for multiple purposes involving different activities at different times, that purpose or use involving the greatest number of occupants shall form the basis for determining the exit requirements.

2.2.4  Non-simultaneous occupancy

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The floor areas of toilets, locker rooms, storage rooms, lobbies, corridors and similar rooms and spaces that serve other rooms and spaces on the same storey but are not occupied at the same time as such other rooms or spaces, can be omitted from the occupant load calculations of that storey of the building on which they are located.

2.2.5 Capacity of exits and exit facilities

R Rationale - Clause 2.2.5

Adhering to the design parameters will prevent overcrowding and will ensure the corridors, exit staircases and doors are adequate in size to receive all the occupants on that floor during evacuation.

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a. The capacity of exits, exit staircases, exit passageways, corridors, exit doors and other exit facilities shall be measured in units of half a metre's width. The number of persons per unit of width shall be determined by the type of occupancy and type of exit as listed under Table 2.2A. In the determination of each exit width, fractions of a unit width less than 250mm shall not be factored in the measurement. Where 250mm or more are added to one or more full units, half of a unit of width shall be factored in.

b.  Where a room or space is required to be provided with two exits, each exit shall be of sufficient width to accommodate not less than half the total occupant load.

2.2.6 Determination of travel distance

The maximum travel distance for the respective types of occupancies shall be not greater than as laid down in Table 2.2A and read in conjunction with all of the following:

a.  In the case of a floor area designed with minimum two exits, the maximum travel distance as given in Table 2.2A shall be applicable. The maximum travel distance starting from the most remote point in any occupied space to the nearest exit, shall not exceed the limits specified in Table 2.2A.

R Rationale - Clause 2.2.6a

The travel distance serves to limit the distance a person is required to travel from the occupied space to an exit staircase door, which every designer should observe. On the other hands, it must also be stated that conforming to the permissible travel distance alone does not necessarily guarantee building occupant life safety during an emergency.

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b. In a large floor area without sub-division of rooms, corridors and so forth, the travel distance can adopt the “direct distance” concept as a guide and shall not exceed two-third of the maximum travel distance permitted under Table 2.2A. Where the large floor area is undergoing sub-division of rooms, corridors, etc. the maximum travel distance shall be in accordance with Table 2.2A.

R Rationale - Clause 2.2.6b

The two-third direct distance method is intended to guide designer for planning of large open floor layout for facilitating flexibility for future inclusions and changes in layout. This guide serves to minimise problem of complying with travel distance during subsequent A/A works.

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c.  For the purpose of this clause, the most remote point from which the travel distance is measured shall be taken as being 400mm from the enclosure walls of the room or space.

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d.  In the case of a residential apartment or maisonette, the travel distance shall be determined based on the provisions under Cl.9.2.1a.(5).

e.  Where area of refuge is provided in lieu of required exits, travel distance shall be measured to the exit door at the corridor leading to the area of refuge.

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f.  Where permitted under Cl.2.3.3 for exit staircases to be entered without the provision of an exit door, the travel distance shall be measured to a position where the exit door would be installed if otherwise required.

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g.  Ancillary office within other purpose groups

Where an ancillary office is housed within a space belong to other Purpose Groups, the travel distance requirement for the ancillary office is allowed to be based on PG IV, provided:

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(1)  the ancillary office is fire compartmented from spaces belonging to the other purpose groups; and

(2)  the ancillary office occupants shall have access to exit(s) within the ancillary office compartment leading to direct discharge at ground level into an external space, into a protected exit staircase or internal/external exit passageway.

2.2.7  Minimum width of exit access door, exit door or other exit facilities

a.  No exit, exit staircase or other exit facilities shall be narrower than the minimum width requirement as specified under Table 2.2A. The minimum clear width of an exit door opening shall be not less than 850mm.

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b.  Exit access doors serving a room with an occupant load of not more than two persons shall not be less than 610mm in clear width.

c. A single leaf swing door along the means of egress shall not exceed 1.25m in clear width.

R Rationale - Clause 2.2.7c

The purpose of controlling the width of single leaf door is to discourage the use of bigger, heavier leaf doors. This is because there is risk of door sagging and thus require more effort to open the door. To overcome it, 2-leaf doors should be used in larger openings instead of single leaf swing door. 

2.2.8 Maximum width of exit staircases

R Rationale - Clause 2.2.8

The purpose of limiting the maximum effective exit capacity of an exit staircase is to prevent concentration of evacuees at any point of the exit. The consequence of permitting exit staircase without capacity limits could be disastrous if that staircase were rendered unusable in an emergency situation. Dividing staircase into segments not wider than 2m enables better crowd control and orderly evacuation in times of emergency.

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a.  The maximum width of exit staircases shall be not more than 2m. Where staircases exceed 2m in width, handrails shall be used to divide the staircase into sections of width not less than 1m or more than 2m.

b.  For the purpose of determining the exit capacity of a staircase that is wider than 2m that forms part of the required means of escape from any storey of the building, that part of its width in excess of 2m shall not be taken into account.

2.2.9  Measurement of width

R Rationale - Clause 2.2.9

The allowance of 80mm projection of handrail is considered acceptable as the projection would normally occur at the waist-height of a person. Therefore, it is unlikely to affect the egress within a protected staircase.

The measurement of width referred to under Cl.2.2.7 and Cl.2.2.8 shall be the clear width, including the width of plinth to balustrade or parapet wall:

a. For an exit staircase

The clear width shall be measured between:

(1) the finished surfaces of the walls, if the staircase is enclosed on both sides by walls only, or

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(2)  the finished surface of the wall and the inner side of the balustrade, if the staircase has a wall on one side and a balustrade on the other side, or

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(3) the inner sides of the balustrades if the staircase has balustrades on both sides.

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Note: The projection of handrail into the clear width of a staircase shall not exceed 80mm on each side of the staircase. If the projection exceeds 80mm, the clear width of the staircase shall be measured from the inner sides of the handrails.

b.  For an exit door

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(1) In the case of an exit door having a single leaf door, the opening shall be measured between the edge of the door jamb and the surface of the door when opened at an angle of 90° (See Diagram 2.2.9b.).

(2) In the case of a 2-leaf exit door fitted with an approved automatic flush bolt, the clear openings shall be measured between the surface of one leaf to the other door leaf when opened at an angle of 90°.

(3)  If one of the door leaves is bolted to the door frame and/or floor by a manually operated bolt, this door leaf shall not be considered for the purpose of determining the exit capacity of the door. The opening of the other door leaf shall have a clear width of not less than 850mm, measured between the edge of the bolted door leaf and the surface of the other door leaf, when opened at an angle of 90°.

(4)  Door hardware and handrails which do not protrude more than 80mm into the clear width of exit opening can be disregarded.

2.2.10  Number of exits from rooms and spaces

There shall be at least two door openings remote from each other which lead to exits from every room or enclosed space in which the total occupant load exceeds the maximum permissible occupant load for one door as listed in the table below:

TABLE 2.2.10 - PERMISSIBLE OCCUPANT LOAD FOR ONE DOOR
Type of Occupancy Max. Occupant Load
High hazard 25
Patient accommodation area 50
Classrooms 50
Godowns, stores, and factories not of high hazard type 50
Assembly 50
Note:
 
(a)       The number and minimum width of exits for rooms and spaces with occupancy of more than 50 persons shall comply with provisions in Table 9.7.3a. for assembly occupancy.
(b)      For residential occupancy, see Cl.9.2.
(c)       For healthcare occupancy, see Cl.9.3.2
(d)      For office/shop/factory/warehouse occupancy, see Cl.9.4, 9.5, 9.6, and 9.8
(e)       For hotels, see Cl.9.7.2
(f)       For assembly occupancy, see Cl.9.7.3.

2.2.11  Number of exit staircases or exits per storey

R Rationale - Clause 2.2.11

Where possible, occupants should not be denied of alternate egress to an exit staircase. By having minimum two exit staircases, it provides an alternative for occupants to access either. This clause also addresses exit provision for non-habitable roofs and incorporates fixed ladder and access hatches requirements.

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There shall be at least two independent exit staircases or other exits from every storey of a building, unless otherwise permitted under other subsequent provisions of the Code. For non-habitable roof, at least one exit staircase shall be provided. Where the area of non-habitable roof is large and one-way travel distance to the exit cannot be met, an additional cat/ship ladder adequately separated in accordance with Cl.2.3.12 and leading to the circulation area of the floor below shall be provided. All access hatches, if provided, shall be readily accessible from the roof. Access hatch opening shall have a minimum clear width of 1m in diameter. The travel distances can be based on that for a sprinkler- protected building for roof areas which are open-to-sky.

2.2.12  Location of exits & access to exits

All exits and access facilities shall be required to comply with all of the following:

a.  Exits and access facilities shall be clearly visible or their locations shall be clearly indicated and shall be kept readily accessible and unobstructed at all times.

b. Every occupant or tenant within a building or storey of a building shall have direct access to the required exit or exits without the need to pass through the spaces or rooms occupied by other occupants or tenants.

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c.  When more than one exit is required from any room or space or a storey of a building, each exit shall be placed as remote as possible from the other as permitted under Cl.2.3.12a., b., c. or d..

R Rationale - Clause 2.2.12c

To reduce the possibility of more than one exit staircase being rendered unusable simultaneously by fire or other emergency situations, the exit staircases are to be remotely located from each other.

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2.2.13  Smoke-free approach to exit staircase

R Rationale - Clause 2.2.13

The smoke-free approach is intended to act as a buffer space to minimise smoke entry into the exit staircase when used by evacuees and firefighters during a fire emergency.

Entry at every storey level (including 1st storey) to an exit staircase serving more than four storeys above ground level shall be through any one of the following:

a.  An external exit passageway or external corridor

The openings for natural lighting and ventilation to the corridor shall be located such that they face and are open to any of the following:

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(1) an external space complying with Cl.2.3.11, or

(2) a street, service road or other public space which is open to the sky, or

(3) an air well which opens vertically to the sky and has a minimum width of 6m and a superficial plan area of not less than 93m², except that for external corridors, it shall comply with the requirements of Cl.2.3.10.

b.  Smoke-free lobby

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(1) A smoke-free lobby shall be separated from the adjoining areas of the building by a wall having 1-hr fire resistance.

(2)  The exit access door shall have ½-hr fire resistance fitted with automatic self-closing device conforming to the requirements of Cl.3.9.2.

(3) The design of a smoke-free lobby shall be such as not to impede movement of occupants through the escape route.

(4) The floor area of a smoke-free lobby shall be at least 3m² and with minimum clear width of 1.2m. If a smoke-free lobby also serves as a fire lift lobby, the floor area shall be not smaller than 6m² and with minimum clear width of 2m.

(5) The floor shall be graded from the lift door towards the lobby door with a fall not exceeding 1 in 200.

(6) A smoke-free lobby, including fire lift lobby, which acts as buffer space for entry into the protected staircase and use by firefighters during emergency, shall be maintained as common property.

(7) A smoke-free lobby shall be ventilated through any of the following:

R Rationale - Clause 2.2.13b.(7)

Access routes to exits shall be kept smoke-free by a smoke-stop lobby, either naturally or mechanically ventilated, in order to provide a reliable means of escape for occupants and access for firefighters.

(a) Permanent fixed ventilation openings which are located in the external wall of the lobby and have a total area of not less than 15% of the floor area of the lobby.

Each opening shall not be less than 1m2 and shall abut an external space or air well, each having a minimum clear area of 93m2 and minimum width of 6m and without obstruction vertically throughout the airspace for ventilation. No part of the lobby floor area shall be more than 9m away from the air well or external space.

R Rationale - Clause 2.2.13b.(7)(a)

The minimum width of 6m and a superficial plan area of not less than 93m² of an air well have been validated through fire engineering study to provide effective smoke ventilation for a smoke-stop lobby.

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(b) Mechanical ventilation, except for PG II buildings, which complies with the requirements in Chapter 7.

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(c)  Cross-ventilated corridor/lobby which complies with all of the following:

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(i) The corridor/lobby shall have fixed ventilation openings abutting an external space. The ventilation openings shall be located on opposite sides of the corridor/lobby at high level and shall not be less than 50% of the superficial area of the opposing external walls.

(ii) No part of the floor area of the corridor/lobby shall be at a distance of more than 12m from the ventilation openings.

(iii) The distance of 12m can be measured along the internal corridor via the intermediate ventilation opening to the external space, provided there is no unprotected openings in the walls along the path to the external space. The intermediate ventilation opening shall not be less than 2m in width and 1.2m in height and the width of the path to the external space shall not be less than 2m.

Note: For residential buildings of habitable height more than 24m with single exit staircase, the requirements for the cross-ventilated corridor/lobby stipulated in Cl.9.2.1a.(4)(e) shall be complied with.

c. Exception

(1) The omission of the smoke-free lobby required under Cl.2.2.13b. leading to the exit staircase of any building exceeding four storeys is allowed under any of the following situations, provided the door opening into the exit staircases shall have 1-hr fire resistance rating and fitted with an automatic self-closing device to comply with the requirements of Cl.3.9.2:

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(a) Where the internal exit staircase is provided with pressurisation up to a habitable height of 24m in compliance with the requirements of Chapter 7;

R Rationale - Clause 2.2.13c.(1)(a)

The positive pressure in the pressurised staircase acts to force smoke away from the doorway of the exit staircase when the exit door is opened, thereby preventing smoke from entering the exit staircase.

(b) Where an external exit staircase is constructed to comply with Cl.2.3.3b.;

R Rationale - Clause 2.2.13c.(1)(b)

Open sides of an external exit staircase allow for quick dispersal of any smoke infiltrated through the doorway when the door is opened. As such, a smoke-stop lobby before the external exit staircase is not necessary.

(c) In an open-sided car park floor where cross-ventilation is provided. In this situation, the fire door to the exit staircase can be ½-hr fire-rated.

R Rationale - Clause 2.2.13c.(1)(c)

The doorway before the exit staircase is unlikely to be smoke logged during a fire emergency. This is because the substantial ventilation openings along the perimeter of the car park allow for quick dispersal of smoke.

(d) On M&E floor of headroom not exceeding 1.5m.

(2) The omission of a smoke-free lobby to exit staircases shall not be allowed under any of the following situations:

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(a) Where the building exceeds four storeys and belongs to PG III or VII.

(b) Where the internal exit staircase, which is provided with pressurisation, exceeds the habitable height of 24m.

(c) Where the exit staircase is adjacent to a fire lift as required in Chapter 6.

2.2.14 Smoke-free approach to exit staircase in basement

R Rationale - Clause 2.2.14

Access to exits must be free of smoke and be available to building occupants at all times. Therefore, a reliable means of escape for occupants and access for firefighters shall be provided via smoke-free access route and staircases. For this reason, providing mechanical air pressuring systems to smoke-stop lobbies and exit staircases is needed to prevent smoke infiltration.

a. In a building comprising more than four basement storeys, the entry to exit staircases serving the basement storeys at every basement storey level shall be through smoke-free lobbies, one of which shall be designated as a fire lift lobby. The exit staircase connecting to the fire lift lobby shall be pressurised to comply with the requirements in Chapter 7.

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b. In a building comprising two, three or four basement storeys, entry at every basement storey level to at least one of the exit staircases serving the basement storeys shall be through a smoke-free lobby. Where only one smoke-free lobby is provided, it shall be required to serve as a fire lift lobby.

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c. Smoke-free lobbies in basement occupancies shall be required to comply with the relevant provisions under Cl.2.2.13b. and shall be mechanically ventilated to comply with the requirements in Chapter 7.

2.2.15 Area of refuge and exit reduction

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When a floor area has access to area(s) of refuge in compliance with all of the following requirements in this Clause, the occupant load for which vertical exits are to be accounted for the floor area can be reduced to half when one area of refuge is provided and to one third when two or more areas of refuge are provided.

a. An area of refuge shall be adequate in size to hold the occupant load it receives from the floor area it serves as provision for required exit, in addition to its own occupant load calculated on the basis of 0.3m2 per person except for healthcare occupancies when the occupant load shall comply with the provisions under Cl.9.3.2b.(4).

b. An area of refuge shall be provided with at least one staircase for use by the occupants to gain access to other exit staircases or the ground level directly to an external space.

c. An area of refuge shall be entered through an external corridor and the room or space or area of refuge shall be separated from the corridor by a wall with at least 1-hr fire resistance rating.

d. External corridors when used as entry into an area of refuge shall conform to the requirements for external exit passageway for minimum width, changes in floor level, roof protection, enclosure on the open side and provision of opening of wall between the room or space and the exit passageway.

e. Exit doors between the room or space or area of refuge and the external corridor shall have fire resistance of at least ½-hr and be fitted with an automatic self-closing device to comply with the requirements of Cl.3.9.2.

f. Every fire compartment in which exit reduction is permitted in connection with area of refuge shall have in addition to exit through the area(s) of refuge at least one exit staircase complying with Cl.2.3.3.