In the UN/DOT system, the hazard class that includes flammable liquids is class number?

• A. 3
• B. 1
• C. 2
• D. 4

Answer: (A)

Flammable liquids are assigned to Class 3 because the primary danger they pose is the potential to ignite and burn easily under normal transport conditions. The UN/DOT system groups materials by their main hazard, and liquids with low flash points—meaning they can produce ignitable vapors at relatively low temperatures—fall into Class 3 to signal this fire risk. This classification guides how they’re packaged, labeled, segregated from other goods, and handled during shipping, storage, and emergency response.

Examples you’d typically see in this class include gasoline and acetone, which have flash points that make them readily ignitable. The other numbers correspond to entirely different hazards: explosives belong to a separate class, gases to another, and flammable solids to yet another. So for liquids that readily ignite, Class 3 is the correct designation.