Fire Prevention and Protection
Content
Fire requires fuel, oxygen, heat, and an uninhibited chemical chain reaction. Prevention removes the combination; protection limits the consequence.
Flammability terms. Flash point is the lowest temperature at which a liquid gives off enough vapor to ignite momentarily; the fire point is slightly higher and sustains burning; autoignition requires no external spark. LFL and UFL bound the flammable range in air, expressed in volume percent. Vapor density and vapor pressure determine where vapors travel and accumulate.
Classes and agents. A: ordinary combustibles (water, foam). B: flammable liquids (foam, CO2, dry chemical). C: energized electrical (CO2, clean agents - de-energize first). D: combustible metals (dry powder, never water). K: cooking oils (wet chemical).
Systems. Know sprinkler types (wet, dry, pre-action, deluge), design density and remote area, standpipes, detection and alarm, smoke control, and NFPA 101 means of egress: exit access, exit, exit discharge, travel distance, occupant load, and clear width.
Special hazards. For combustible dust, MEC, MIE, Kst, and Pmax drive deflagration venting, isolation, and inerting decisions.
Traps. Confusing flash point with autoignition temperature; using water on a Class D or Class K fire; and assuming a sprinkler system protects a commodity or storage arrangement it was never designed for.
Worked example
A liquid with a flash point of 38 C (100 F) is a Class II combustible liquid under NFPA 30, not a Class I flammable liquid, which is anything below 37.8 C. The class drives storage and handling requirements.