What should the explosimeter reading be for safe tank entry?

The correct answer regarding the safe explosimeter reading for tank entry is 0% of the Lower Explosive Limit (LEL).

When entering a confined space such as a tank, it is critical to ensure that the atmosphere is safe from the presence of flammable gases or vapors. The LEL represents the lowest concentration of gas in the air that can ignite and cause an explosion. Therefore, a reading of 0% LEL indicates that there is no combustible gas present in the atmosphere, which is essential for maintaining safety during tank entry operations.

While other readings, like 50%, 25%, or even 75% of LEL, suggest varying degrees of risk depending on the percentage, any positive reading of LEL indicates the presence of flammable vapors, which can pose a significant hazard to personnel. For safety protocols, it is crucial to always achieve a reading of 0% LEL before allowing anyone to enter the tank. This ensures that the environment is free of combustibles, minimizing the risk of fire or explosion.