What hazard is associated with materials classified as Dangerous When Wet?

Materials classified as Dangerous When Wet are those that can potentially combust or release flammable gases upon contact with water. This characteristic is critical because when these substances interact with water, they may undergo chemical reactions that result in the liberation of gases that can ignite, leading to hazardous situations.

The designation of "Dangerous When Wet" highlights the need for specialized handling and storage practices to prevent water exposure. Understanding this hazard is vital for ensuring safety during transportation, storage, and emergency response to incidents involving these materials.

In contrast, the other options touch on conditions or behaviors that do not apply to the unique risks posed by Dangerous When Wet substances. Some may not emit toxic gases merely by being dry, and not all require refrigeration; these characteristics do not capture the core hazard associated with their reaction to water.