Building Construction, Fire Behavior, and Fire Protection Systems
Buildings, fire behavior, and systems
Know the five construction types: Type I (fire-resistive), Type II (noncombustible), Type III (ordinary, exterior masonry with combustible interior), Type IV (heavy timber), Type V (wood frame). Type I offers the most resistance; Type V the least. A frequent trap is confusing Type IV heavy timber with Type V wood frame, or assuming a modern lightweight truss performs like legacy dimensional lumber. Lightweight construction fails faster under fire.
Fire behavior: ignition, growth, flashover, fully developed, decay. Pyrolysis is thermal decomposition producing combustible vapors; backdraft is a deflagration from oxygen introduction into a fuel-rich compartment; smoke explosion is ignition of accumulated smoke. Ventilation changes the fire environment, sometimes improving conditions and sometimes not.
Fire protection systems: sprinklers, standpipes, fire pumps, alarms, FDCs, and PIVs. Know that sprinklers are designed to control or extinguish depending on design, and that a closed PIV or obstructed FDC can defeat the system. Fire flow and occupancy hazard drive system design.
Worked example: On arrival, you see a sagging roof over a strip center with lightweight trusses and smoke showing from the eaves. Treat the roof as unstable, avoid operating under it, and consider defensive tactics unless savable lives require entry.
Rule of thumb: Construction type and fire load tell you how long you have, and lightweight construction shortens that clock.