What should be checked before opening a valve on a tank containing hazardous materials?

Before opening a valve on a tank containing hazardous materials, it is crucial to check the valve's operational condition. This ensures that the valve is functioning correctly and can be safely operated without the risk of leaks or malfunctions that might release hazardous materials into the environment or pose a risk to personnel.

Ensuring that the valve operates properly minimizes the likelihood of accidents such as spillage or accidental exposure to hazardous substances. A malfunctioning valve could fail to close properly, or even burst under pressure, leading to significant safety hazards. Therefore, verifying the operational condition of the valve is a critical step in maintaining safety during the handling of hazardous materials.

While checking other factors such as the specific gravity, temperature of the liquid, and pressure in adjoining lines can provide valuable information regarding the conditions within the tank, they do not directly address the immediate safety concern of the valve itself. The valve's state is paramount, as it is the critical point where the hazardous material could escape if not functioning properly.