Introduction

This section provides additional guidance (see 1.1.2) for protected corridors / lobbies which provide means of escape from flats.

1.7.1 Corridor / Lobby Travel Distances in buildings with a Single Stairway

All common protected corridors / lobbies which have direct access to a flat should be ventilated by means of a smoke control system.

An exception to this requirement is a building with a topmost floor level of less than 11 m. In such a building, where a smoke control system is not provided, the maximum travel distance (see 1.1.2) is

4.5 m.

The maximum travel distance in a protected corridor / lobby provided with a smoke control system (see 1.7.2), irrespective of the topmost floor level, is 7.5 m.

Where every flat to a protected corridor / lobby on the same storey is provided with a sprinkler system (see 1.8), and the same protected corridor(s) / lobby(s) are provided with a smoke control system, the travel distance on that storey can be further extended up to a maximum of 15 m.

The travel distance should be measured from the furthest entrance door to a flat to the protected stair, or lobby door. The lobby should provide direct access to the stair and should not provide direct access to a flat or ancillary accommodation.

1.7.2 Smoke Control System for Protected Corridors / Lobbies

A smoke control system for a protected corridor / lobby is installed to facilitate escape in corridors / lobbies. The smoke control system should be designed to ventilate the protected corridor / lobby for means of escape. The smoke control system should be activated by means of an appropriate fire detection and alarm system.

The smoke control system should consist of (a), (b), or (c), as follows:

(a) an automatic opening vent having a clear openable area of not less than 1 m2 fitted at the top of the stairway enclosure, and an automatic opening vent(s) (AOV) from the protected corridor / lobby to the exterior of the building, which should be in accordance with the following:

(i) it should have a minimum free area of 1.5 m2,

(ii) it should be fitted as close to the top of the ceiling of the protected corridor / lobby as is practicable, but be at least as high as the top of the door connecting the protected corridor / lobby to the stairwell or lobby.

Where there are multiple AOV’s due to multiple corridors, the system should be designed to activate the relevant AOV only. The AOV’s from the common protected corridors / lobbies on all other floors should remain closed.

(b) an automatic opening vent having a clear openable area of not less than 1 m2 situated at the top of the stairway enclosure, and an automatic opening vent to a natural smoke shaft, which should be in accordance with 1.7.3 below.

(c) a mechanical smoke control system which has a proven equivalent performance to (a) or (b) above.

In a building with a floor level at more than 20 m above ground level, the provision of an adequate smoke control system to a protected corridor / lobby may be sufficient to ventilate the firefighting lobby (see 5.3).

Where any smoke control system is powered by electricity, the system should be capable of operating at all material times.

1.7.3 Natural Smoke Shafts in buildings containing Flats

Natural Smoke Shafts in buildings containing flats should be closed at the base. Replacement air is provided from the automatic opening vent in the stairwell to help the efficiency of the shaft system.

Natural smoke shafts should meet the following specific recommendations:

(i) the smoke shaft should have a minimum cross-sectional area of 1.5 m2 (minimum dimension 0.85 m in any direction),

(ii) the minimum ventilation area from the protected corridor / lobby into the shaft, and at the opening at the head of the shaft, and at all internal locations within the shaft (e.g. safety grilles) should be at least 1m2,

(iii) the top of the protected corridor / lobby vent should be located as close to the ceiling of the protected corridor / lobby as is practicable, and should be at least as high as the top of the door connecting the protected corridor / lobby to the stairwell or lobby,

(iv) the shaft should extend a minimum length of 2.5 m above the ceiling of the highest storey which is served by the shaft,

(v) the opening at roof level should be at least 0.5 m above any surrounding structures within a horizontal distance of 2.0 m,

(vi) the smoke shaft should be constructed in accordance with 3.2.7.1,

(vii) the ventilation openings from the protected corridor / lobby to the vent shaft should achieve the same fire performance as the shaft, but not exceeding 60 minutes,

(viii) no services other than those relating to the smoke shaft should be contained within the smoke shaft,

(ix) the shaft should be vertical from base to head but may have not more than 4 m at an inclined angle not more than 30◦ from the vertical plane,

(x) the design of the system should be such that, on activation of the fire detection and alarm system, the ventilator on the fire floor, the ventilator at the top of the smoke shaft and the 1m2 ventilator at the head of the stairway should all open simultaneously.

Where there are multiple shafts due to multiple corridors, the system should be designed to activate the relevant shaft only. The ventilators from the common protected corridors / lobbies on all other floors, and unaffected corridors on the fire floor should remain closed.

1.7 Protected Corridors / Lobbies Serving all Flats

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