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Difficulty: HardFire Safety and Classification

In an automotive repair facility, technicians handle a wide variety of flammable substances, electrical equipment, and structural materials. Match each shop fire hazard scenario with its appropriate fire extinguisher classification and extinguishing mechanism.

  • Solvent-soaked rags and pooled motor oil in a parts degreasing bayClass B (Smothers flammable liquid vapors and suppresses chemical chain reactions)
  • Combustible magnesium steering components and titanium grinding shavingsClass D (Employs specialized dry powder agents to smother and absorb heat from combustible metals)
  • Wooden shipping crates and cardboard parts packaging in the stockroomClass A (Cools and quenches ordinary fibrous combustibles with water or multipurpose dry chemical)
  • Arcing, energized circuit breaker panel supplying power to a hydraulic vehicle liftClass C (Utilizes non-conductive extinguishing agents to safely suppress energized electrical fires)

Answer

Solvent-soaked rags and pooled motor oil match Class B; magnesium components and titanium shavings match Class D; wooden crates and cardboard packaging match Class A; and an energized circuit breaker panel matches Class C.
Each fire hazard is correctly paired based on standard National Fire Protection Association (NFPA) classifications: ordinary combustibles like wood/cardboard belong to Class A; flammable liquids and grease belong to Class B; energized electrical components belong to Class C; and reactive combustible metals like magnesium belong to Class D.

Step-by-Step Solution

1
Classify the ordinary solid fibrous combustibles
Wooden crates and cardboard packaging burn to create ash and ember, which defines a Class A fire requiring quenching/cooling.
Class A covers common solid combustible materials such as wood, paper, textiles, and rubber.
2
Classify the flammable liquid and solvent hazard
Solvents, fuels, and motor oils represent liquid and vapor combustion, which defines a Class B fire.
Class B extinguishers are engineered to smother liquid vapors without splashing the burning fluid.
3
Classify the live electrical hazard
The energized circuit breaker panel carries active current, defining a Class C fire.
Class C extinguishers use non-conductive agents (such as CO₂ or dry chemical) to protect the technician from electrical shock.
4
Classify the combustible metal hazard
Magnesium and titanium shavings ignite at very high temperatures and react violently with conventional agents, defining a Class D fire.
Class D fires require specialized dry powder agents (such as sodium chloride or copper-based powders) that do not release moisture.

Key Concept

Standard Shop Fire Classification (Classes A, B, C, and D) and Extinguishing Agent Compatibility
Estimated Time:1m 30s
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Topics

Fire Safety and Classification

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