Tankers carrying cryogenic cargoes, such as LNG, are fitted with gas detector systems alarmed at 30% of the lower explosive limit. If the gas detector alarms sounds, this means __________.

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

An alarm at 30% of the Lower Explosive Limit indicates the vapor concentration is flammable but currently too lean to support combustion. This provides a critical safety margin, allowing crew members to identify and rectify leaks or ventilation issues before the atmosphere reaches the explosive range.