Fire Behaviour and Building Protection

How fire develops

Fire requires fuel, oxygen and an ignition source, sustained by a chemical chain reaction. Removing any one extinguishes it, which is the principle behind every extinguishing method.

A fire in a room grows slowly at first, then very rapidly. The critical phenomenon is flashover: as hot gases collect at ceiling level and radiate downward, every combustible surface in the room reaches ignition temperature almost simultaneously and the entire compartment becomes involved. This can occur within a few minutes of ignition in a furnished room, and survival in the compartment after flashover is not possible. Everything about escape planning is governed by the time available before this point.

Smoke is the danger

The majority of fire deaths result from smoke and toxic gases rather than burns. Modern furnishings and plastics produce dense, highly toxic smoke very quickly. Smoke also removes visibility almost completely — people who know a building well become disoriented in it within a few metres. This is why smoke control, protected escape routes and clear signage matter more than extinguishers.

How buildings are designed to resist fire

• Compartmentation — dividing the building into fire-resisting compartments that contain fire and smoke for a defined period, giving time for escape and for the fire service to act. This is the foundation of building fire safety and it is also the most frequently and most casually breached.
• Fire doors — the moving part of a compartment wall. They work only when closed, correctly gapped, fitted with intact intumescent strips and smoke seals, and self-closing properly. A wedged-open fire door defeats the compartment entirely.
• Fire stopping — sealing around every service penetration through a compartment wall or floor: cables, pipes, ducts. New penetrations made during works and not resealed are extremely common and entirely invisible above a ceiling tile.
• Protected escape routes — corridors and stairways constructed to resist fire and kept free of combustible material and obstruction.
• Structural fire protection — maintaining structural stability during a fire.
• External wall construction — subject to significantly increased scrutiny and regulation in many jurisdictions following major incidents, with obligations on assessment and remediation.

Duties

Legal frameworks vary substantially by country, and they share a common structure: a defined person or organisation is responsible for fire safety in a building; that person must assess the risk, implement and maintain appropriate measures, provide information and training, and keep records. In multi-occupied buildings duties are shared and must be coordinated, and the division between landlord and tenant is set by the lease and is frequently misunderstood by both.

Penalties for serious breaches include prosecution and imprisonment in many jurisdictions, and enforcement has intensified. Confirm the framework applying to your building and take competent advice — this course describes structure and practice, not any single legal system.

Building information

Know your building: its construction, compartment lines, escape routes, system types and locations, and any known deficiencies. Hold the fire strategy document if one exists, the as-built drawings, and the record of any alteration. Buildings are altered repeatedly over their life, and the fire safety implications of those alterations are frequently never assessed.