Fire spread (Dutch: brandoverslag) is the phenomenon where fire extends from its original location to adjacent buildings or spaces through radiation, convection, or direct flame contact. It occurs when the heat released by a fire is intense enough to ignite materials in nearby structures, even without direct flame contact.
How fire spread occurs
Fire spread can happen through several mechanisms:
- Radiation — heat waves travel through the air and heat the surface of a neighbouring building until it reaches ignition temperature
- Convection — hot gases and flames rise and travel horizontally, carrying heat to adjacent compartments or buildings
- Direct flame impingement — flames extend through openings such as windows or ventilation grilles and ignite combustible surfaces nearby
- Flying brands — burning debris carried by wind or updrafts lands on combustible roofing or other surfaces at a distance
Factors that influence fire spread
- Distance between buildings — shorter distances increase the risk dramatically
- Size and number of openings — windows and doors act as radiating surfaces once the glass breaks
- Wind speed and direction — wind accelerates flame travel and carries embers
- Facade material — combustible cladding allows fire to climb vertically and spread laterally
- Fire load — the amount of combustible material inside a compartment determines heat output
Application
Fire spread is a key consideration in building regulations and urban planning. Building codes specify minimum separation distances between structures, fire-rated facade requirements, and compartmentation rules to contain fire within its area of origin. Fire engineers use radiation calculations to demonstrate that adjacent buildings will not ignite within the time needed for evacuation and fire service intervention.
Related Terms
- Fire resistance
- Fire rating
- Fire prevention
- Compartmentation
- Facade cladding
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