Fire Fighter I: Fire Behavior, PPE, Hose Hydraulics, and Fire Classes
Fire behavior
Fire Fighter I items range widely, but most cluster around a few core ideas: the fire tetrahedron (fuel, oxygen, heat, chemical chain reaction), how ventilation changes it, and how to read smoke. Know the difference between flashover - everything in the compartment ignites at once from radiant heat feedback - and backdraft - an oxygen-starved fire admits air and burns explosively. Flashover is heat-driven; backdraft is oxygen-driven. Question writers swap these definitions deliberately.
Standards and equipment
NFPA 1001 is the qualifications standard you are testing against; NFPA 1971 covers structural protective clothing; NFPA 1981 covers SCBA. Know SCBA limits: most units are rated 30 or 45 minutes, but that rating assumes a low work rate, so actual working time is much shorter.
Ladders and hose hydraulics
An extension ladder reaches higher than its bedded length suggests: a 24-ft ladder reaches the second floor. Set the tip even with or just above the sill and the butt about one-quarter of the working length from the wall.
Friction loss climbs with the square of the flow. Worked example: 200 ft of 1¾-in. hose flowing 150 gpm into a 100-psi nozzle. Q = 150/100 = 1.5. FL = C Q² L with C = 15.5 → 15.5 × 2.25 × 2 = 70 psi. Pump discharge = nozzle pressure + friction loss + appliance loss + elevation = 100 + 70 = 170 psi.
Fire classes and agents
A: ordinary combustibles (water); B: flammable liquids (foam, CO2); C: energized electrical (de-energize first); D: combustible metals (dry powder); K: cooking oils (wet chemical).