Span gas is used aboard liquefied natural gas carriers to __________.

Correct Answer: Option B — calibrate the gas leak detectors

Span gas is a certified reference gas mixture used to verify the accuracy of gas detection sensors. Regular calibration, as required by 46 CFR 154, ensures that methane detectors provide reliable readings, preventing catastrophic failure of safety systems on LNG carriers by confirming the equipment responds correctly to known concentrations.