Difficult evacuations

Originally, provision was made for horizontal exits between fire compartments because some occupants can have difficulty evacuating, particularly those confined to bed or that have a disability.

Subsequently, it was accepted that horizontal exits would be of value in other buildings, where they could overcome problems associated with large fire compartments, e.g. excessive distances to travel to exits.

Purpose of horizontal exits

The use of horizontal exits can overcome some of the difficulties outlined above, although they need to be used in conjunction with some other form of exit.

In an emergency, the Deemed-to-Satisfy Provisions require that occupants travel for limited distances before they reach a place of safety. A “place of safety”, in the case of horizontal exits, means the connecting fire compartment to which people will flee.

For a horizontal exit to comply with the Deemed-to-Satisfy Provisions of Section D, it must meet the following criteria:

• The distance of travel to the exit must not exceed that specified elsewhere in the BCA.
• The protection for a place of safety from its adjoining fire compartment is provided by a fire wall. The fire wall has a fire rating to match the classification of the fire compartments it divides and is expected to withstand a burnout of the respective areas. This provides an appropriate level of safety to people using the horizontal exit as they may have to remain in the place of safety for an extended period before evacuating via other exits.
• There must be another exit (other than a horizontal exit) from each place of safety entered by way of a horizontal exit. After escaping to the place of safety it should not be necessary to return to the area being evacuated to continue to evacuate from the building. D2D16(3) specifies a limit for the number of horizontal exits in a storey for buildings of other than Class 9a and Class 9c buildings.
• The place of safety must be large enough to temporarily accommodate the people from the area the horizontal exit is being provided for. It is important to note that if there is only one other exit in the fire compartment then the place of safety is to be large enough to accommodate all the occupants of the fire compartment. This is necessary because if the other exit is blocked then all the occupants will be required to exit through the horizontal exit. This is necessary until vertical evacuation is available. Since this accommodation is only for a short period, the areas specified generally only allow for people to stand. However, the larger areas specified for Class 9a health-care buildings and Class 9c buildings allows for patients or residents on beds to be wheeled through the horizontal exit to be accommodated in the place of safety.
• The path to the place of safety is to have dimensions equal to those of the horizontal exit to assist with the smooth evacuation of occupants.
• The swing of the horizontal exit door must be the same as other exit doors. This means that if the area is more than 200 m2 (as specified in D3D25(1)(b)), the door is to swing in the direction of egress. If the FRL of the fire wall is three or four hours, two fire doors may be provided to achieve this FRL. In such cases, for both doors to swing in the one direction, a vestibule must be formed, as shown in Figure D2D16.
• For a Class 9b early childhood centre, the clear area required by D2D16(4) must be large enough to accommodate all occupants of that storey of the early childhood centre. 
• To make sure that evacuation is always possible, it is not permitted to have a horizontal exit to a separate sole- occupancy unit. This is because the owner or occupier of the other unit may lock the door for security reasons, barring entry (or exit) in an emergency.
• Where egress is required in either direction, two doors swinging in opposite directions or a 180° swinging door (complying with all BCA requirements including fire and smoke sealing capacities) may be used.

Other uses of horizontal exits

Horizontal exits may be useful as a means of evacuation from many health-care buildings. They can also be an advantage in large floor area buildings which need to be sub-divided by fire walls to reduce the size of the fire compartments. These fire walls can then be penetrated to create horizontal exits.

Figure D2D16: Plan showing doors forming a horizontal exit in a fire wall in accordance with D2D16