A tank or compartment is "gas free" when there is an absence of dangerous concentrations of __________.

Correct Answer: Option B — flammable or toxic gases

A space is defined as gas-free when atmospheric testing confirms that concentrations of flammable vapors are below the Lower Explosive Limit (LEL) and toxic gases are below the Permissible Exposure Limit (PEL). This ensures the environment is safe for human entry and hot work operations.