Two sets of breathing apparatus should be brought to the entrance to the space and tested before anybody enters the space. The test should confirm that the apparatus is in working order, with fully charged air cylinders.
A stretcher is needed to lift anyone collapsed or injured. Tanks usually have lightening holes and many standard stretchers will not go through them. Do check the stretchers you have onboard. Flexible stretchers that have been designed for use in confined spaces are available from manufacturers.
Crew may not be physically capable of lifting a large person by rope, particularly where this has to be done over a great height. Conditions can also be very dangerous for the person being lifted. Ships should consider installing a rescue tripod or similar system that can be erected over an access hatch for the purpose of rigging a block for lifting a casualty to deck level. Consider welding lifting pad eyes to enclosed spaces to facilitate rescue, and carrying out regular inspection.