• in passenger ships, they are not to require penetration
below the top of the tank and their failure or overfilling
of the tanks is not to permit release of fuel
• in cargo ships, their failure or overfilling of the tank is
not to permit release of fuel into the space. The use of
cylindrical gauges is prohibited. The Society may permit
the use of oil-level gauges with flat glasses and self-closing
valves between the gauges and fuel tanks.
• their glasses are to be made of heat-resistant material
and efficiently protected against shocks.