Tankers carrying cryogenic cargoes, such as LNG, are fitted with gas detector systems alarmed at 30% of the lower explosive limit. What is indicated if the gas detector alarms sounds?

Correct Answer: Option C — a flammable vapor concentration exists at the sample point, but it is too lean to burn

An alarm sounding at 30% of the Lower Explosive Limit (LEL) indicates that flammable vapor is present at the sampling point, but its concentration is far below the minimum threshold required for ignition, meaning the mixture is still too lean to burn.