Which body of rules helps determine if a cargo tank is safe to enter after cleaning?

• A. Visual inspection alone
• B. Atmosphere testing results per MARPOL/ISM procedures; a gas-free certificate confirms safety for entry.
• C. Random guess
• D. Advice from supervisor

Answer: (B)

Safety for entering a cleaned cargo tank relies on proven conditions of the space’s atmosphere, not on appearance or guesswork. MARPOL and the ISM Code require that the space be tested for harmful conditions before anyone goes inside. This means calibrated detectors are used to measure the oxygen level and check for flammable or toxic gases. When the atmosphere is within the defined safe limits, a competent person issues a gas-free certificate, which formally authorizes entry and becomes part of the ship’s safety documentation. Visual checks or taking someone’s word isn’t enough because dangerous vapors or oxygen deficiency aren’t visible or detectable without proper testing. Relying on supervision alone isn’t a substitute for the measured, official confirmation provided by the gas-free certificate.