In the UN/DOT Marking System, which of the following substances falls under Hazard Class 3?

• A. Butane
• B. Gasoline
• C. Chlorine
• D. Ammonia

Answer: (B)

The correct answer reflects that gasoline is classified under Hazard Class 3 in the UN/DOT Marking System. Hazard Class 3 refers specifically to flammable liquids, which are defined as liquids that have a flash point of 60°C (140°F) or lower. Gasoline, commonly used as a fuel, has a flash point significantly below this threshold, making it a clear candidate for this classification due to its flammable properties.

While butane is also a flammable substance, it is typically classified differently. Chlorine falls under Hazard Class 2 because it is a toxic gas and an oxidizer, while ammonia, though it can present flammability hazards under certain conditions, is primarily classified under Hazard Class 2 as a toxic substance. Thus, gasoline is the only substance listed that fits the criteria for Hazard Class 3, highlighting its significant risks when being transported or stored.