What Is Fire Compartmentation?

Fire compartmentation is the division of a building into separate fire-resistant volumes — called fire compartments — designed to contain the spread of fire and smoke to the compartment of origin for a specified period of time. It is the single most important passive fire protection measure in most buildings and the foundation on which all other fire safety provisions are built.

The principle is straightforward: if a fire starts in one compartment, the fire-resistant construction forming the compartment boundaries should contain it long enough for occupants to escape and for the fire service to intervene. Without effective compartmentation, fire can spread rapidly through a building, overwhelming escape routes and making firefighting difficult or impossible.

What Forms the Compartmentation?

• Fire-rated walls and partitions — specified to achieve a defined fire resistance period (typically 30, 60, 90 or 120 minutes) for a combination of integrity, insulation and load-bearing capacity
• Fire-rated floors — particularly in multi-storey buildings where fire and smoke spread vertically is a primary concern
• Protected shafts — stairwells, lift shafts and service risers that penetrate multiple compartments must themselves be protected to contain spread
• Fire doors — the weakest element in any compartment wall; fire doors must be correctly specified, installed and maintained
• Fire stopping — all penetrations through compartment walls and floors for services, cables and pipes must be fire stopped to prevent smoke and fire passage through gaps

Why Compartmentation Fails

Fire compartmentation failure is one of the leading causes of fire fatalities in buildings. The most common failure modes are:

• Missing or poorly installed fire stopping around service penetrations
• Damaged or held-open fire doors
• Incorrectly specified fire-rated partitions
• Inadequate compartmentation between different occupancies in mixed-use buildings
• Undetected voids and cavities that allow fire and smoke to travel between compartments

Compartmentation in Fire Strategies

The fire strategy for a building sets out the compartmentation design — the location and specification of compartment walls and floors, the fire resistance periods required for each element, the fire door strategy, and the fire stopping requirements. Without a robust compartmentation strategy in the fire strategy, the construction team have no definitive specification to build to — and the building's fire safety depends on whoever happens to be making decisions on site.