Which hazard class is represented by the placard illustration that states 'Dangerous when wet'?

Which hazard class is represented by the placard illustration that states 'Dangerous when wet'?

• A. Dangerous when wet
• B. Radioactives
• C. Poison gases
• D. Corrosives

Answer: (A)

That placard warns about materials that react with water to release flammable gas. It’s the label used for Class 4.3 (water-reactive substances). The phrase “Dangerous when wet” tells responders to keep the material dry and avoid contact with moisture, since exposure to water can generate flammable gas. This is distinct from other hazard classes shown in the other options—radioactive materials (Class 7), toxic gases (Class 2), and corrosives (Class 8)—which use different signs and warnings.

That placard warns about materials that react with water to release flammable gas. It’s the label used for Class 4.3 (water-reactive substances). The phrase “Dangerous when wet” tells responders to keep the material dry and avoid contact with moisture, since exposure to water can generate flammable gas. This is distinct from other hazard classes shown in the other options—radioactive materials (Class 7), toxic gases (Class 2), and corrosives (Class 8)—which use different signs and warnings.