Fire-induced pressure and smoke spreading in mechanically ventilated buildings with air-tight envelopes

Fire-induced pressures have not been considered dangerous in building fires, but the situation may be changing as building envelopes become increasingly air-tight. In this study, we investigate whether this can change the fire development and pose new risks for structural and evacuation safety. We used experiments to validate the numerical models, and models for simulating the fire development in buildings with different air-tightness levels. The simulations considered air permeability values typical for traditional, modern and Near-Zero buildings. Three different smoke damper configurations were studied, and the fire growth rates were varied from medium to ultra-fast. The results showed that transitioning from traditional and modern buildings to Near-Zero buildings can sufficiently increase the peak overpressures from fast-growing fires to cause structural damage. Conditions were identified for avoiding excessively high overpressures, while preventing smoke from spreading through the ventilation system.