Hazmat division 4.3 hazard is ...

• A. Flammable Solids
• B. Spontaneously Combustible
• C. Oxidizers
• D. Dangerous when Wet

Answer: (D)

Division 4.3 refers to materials that are dangerous when wet. These substances react with water to release flammable or toxic gases, which can ignite or explode in moisture or when exposed to humidity. That moisture-triggered hazard is what defines Division 4.3.

For example, some materials release flammable gases like acetylene when they come into contact with water, and alkali metals such as sodium can violently react with water to produce hydrogen gas and heat. That moisture-triggered reaction is the hallmark of this division.

The other options describe different hazard classes: flammable solids belong to Division 4.1, spontaneously combustible materials to Division 4.2, and oxidizers to Division 5.1. They do not exhibit the moisture-triggered gas release that characterizes Division 4.3.