COMMENTARY ON CLAUSE 12

a) Primary Objective:

● Ensure occupants can reach a place of ultimate safety outside the building during a fire.

b) Categories of Evacuation Procedures:

● Total Evacuation:

● All occupants evacuate to safety either simultaneously or in phases.

● Progressive Evacuation:

● Occupants move to a place of relative safety within the building and, if needed, complete evacuation to ultimate safety as part of a managed system.

c) Special Considerations:

● Recommendations for means of escape for disabled people are detailed in Clause 45.

12.1 General

Independence: Evacuation strategy should not depend on external help.

Risk Profile: Tailor the strategy to the building's specific risks.

Travel Time: Ensure the strategy accommodates allowable travel time for evacuation.

12.2 Total evacuation

12.2.1 Simultaneous evacuation

Default Approach: Use simultaneous evacuation if occupants cannot stay in the building long during a fire.

Alarm Arrangement: Follow BS 5839-1:2013 for appropriate alarm systems.

Escape Stairs: Ensure stair widths comply with section 17.4.2.

NOTE This takes into account not only the physical effects of the fire, but the psychological response of occupants confronted by an outbreak of fire.

12.2.2 Phased evacuation

COMMENTARY ON 12.2.2

a) Phased Evacuation: Used in high-rise buildings with fire-resisting floors or certain atrium buildings.

b) Evacuation Order: Evacuate the most affected floor and those with impaired evacuation ability first, then evacuate remaining floors in phases, usually two at a time.

c) Space Efficiency: Reduces space needed for stairways but requires extra fire protection and management measures.

d) Stair Widths: Follow recommendations in section 17.4.3.

e) Conditions for Phased Evacuation:

● Stairways: Must have a protected lobby, corridor, or pressure differential system.

● Compartment Floors: Every floor must be a compartment floor.

● Sprinkler System: Automatic sprinkler system required if any floor is over 30m above ground, conforming to BS EN 12845.

● Fire Alarm: System must meet L3 standard per BS 5839-1:2013, with voice alarm as per BS 5839-8:2013.

● Emergency Communication: Voice communication system per BS 5839-9:2011, with outstations at each floor and a master station at a control point.

● Lifts: Should be accessed through a protected lobby.

12.3 Progressive evacuation

COMMENTARY ON 12.3

Categories of Progressive Evacuation:

Progressive Horizontal Evacuation:

● Evacuate people to an adjacent fire compartment on the same level.

● Later move them to a place of ultimate safety.

Zoned Evacuation:

● Used in large retail developments to avoid operational loss from evacuating the entire building for a small fire.

● Move occupants from the affected zone to an adjacent zone.

● Example: In a shopping center, move people to an adjacent smoke control zone while controlling the fire in the affected zone.

Additional Measures:

● Requires extra passive and active fire protection measures.

● Needs supportive management arrangements.

12 Evacuation strategy