FSS 2.2.13 – Smoke Free Approach to Exit Staircase




FSS  No:






Entry at every storey to an exit staircase without opening to natural light and ventilation (i.e. natural ventilation) of any building or part of a building of more than four storeys above ground level shall be through a lobby that is separated from the adjoining areas of building by a wall having a fire resistance of at least 1 hour. Similar requirement shall also apply to staircase serving more than 4 basement storeys.

Definition of smoke-stop lobby


A smoke stop lobby, including fire-fighting lobby, which acts as buffer space for entry into the protected staircase and use by fire fighters during emergency, shall be maintained as common property.

Purpose of smoke-stop lobby


Floor area of smoke-stop lobby shall not be less than 3m2, and if a smoke-stop lobby also serves as a fire fighting lobby, the floor area shall not smaller than 6m2 and with no dimension smaller than 2m. Fire fighting lobby shall also be provided for fire lift. The floor shall be graded from the lift door towards the lobby door with a fall not exceeding 1 in 200.

Dimension of smoke-stop lobby


A smoke-stop lobby can be ventilated by the following approaches:

  • Permanent fixed ventilation openings in the external wall of the lobby; such ventilation openings shall have an area of not less than 15% of the floor area of the lobby and located not more than 9m from any part of the lobby, or
  • Pressurisation system using ventilation fan shall be provided for the smoke-stop lobby and pressure gradient shall be such that the pressure at the exit staircase shall always be higher, or
  • Cross-ventilated corridor having fixed ventilation openings in at least 2 external walls. The openings to each part of the external walls shall not be less than 50% of the superficial area of the wall enclosing the corridors No part of the floor area of the corridor shall be at a distance of more than 13m from any ventilation openings.

Permanent fixed ventilation opening to an open air well which is open vertically to the sky for the full height of the building is allowed. The air well shall have a horizontal plan area of not less than 10m2 or 0.1m2 for each 300mm of height of the building, whichever is the greater. The minimum width of such space shall not be less than 3m. The enclosure walls to the air well shall have a minimum fire resistance of 1 hour and have no openings except for the smoke-stop lobby, exit staircase and toilet.

Ventilation requirement


Omission of smoke-stop lobby required to exit staircase of any building exceeding 4 storeys is allowed with compliance of following requirements:

  • The internal exit staircase is provided with pressurisation up to a habitable height of 28m, or
  • The external exit staircase is located along its perimeter wall and provided with uninterrupted external ventilation openings having not less than 50% of the superficial wall area of the staircase at each storey level, or
  • Beside having the above-mentioned wall opening, external exit staircase can be located within or abutting an airwell (which is open to sky and is required to provide lighting and ventilation to the occupancy areas) having the minimum size in relation to the habitable height of the building:

Maximum Habitable Height of Building

Minimum Clear Width of Airwell









60m and above



Omission of smoke stop lobby is allowed


Omission of smoke-stop lobby to exit staircases shall not be allowed under the following situations:

  • Where the building exceeds 4 storeys and belongs to place of public resort;
  • Where the internal exit staircase, which is provided with pressurisation, exceeds the habitable height of 23m;
  • Where the exit staircase is designated as fie fighting staircase adjacent to a fire lift.

Omission of smoke stop lobby is not allowed


In a building comprising more than 1 basement storey, entry at every basement storey level to at least one of the exit staircases serving the basement storeys shall be through a smoke-stop lobby and where only one smoke-stop lobby is provided, it shall be required to serve as a fire fighting lobby.

Entry at basement


A fire lift shall be adjacent and accessible to an exit staircase and be approached by a fire fighting lobby at each storey. Similar to smoke-stop lobby, fire fighting lobby shall also be pressurised with at least 1 hour fire resistance.

Fire fighting lobby

Prepared by: Yeo Swee Khiank


06 December, 2007


Annex A


Annex B


Annex C



Annex D
Annex E


Annex F


Annex G

Annex  H



Annex I





Annex J


Annex K


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