To help ensure effective use of isolation valves it's recommended that those
which are not immediately adjacent to appliances should be clearly marked to
the appliance they serve.

For ease of use if valves operate by rotation it's recommended that they are
closed by turning clockwise. It's also a good idea to mark the 'open' and 'closed'
positions on or next to each of the valves on your boat.

Using unsuitable valves can allow gas to leak. Plug valves must be springloaded
and needle valves must not be used.

Accidentally switching a valve on could lead to an unnoticed accumulation of
gas. To help prevent this happening, valves at floor level must be located so
they can't be inadvertently activated, or they must be of the drop fan or loose
key type.

If pipework is not sealed effectively from appliances which have been
permanently removed or temporarily removed for servicing, gas will leak. To
prevent this from happening, pipework to such appliances must be properly
plugged or capped. Isolation valves alone are not sufficient for this purpose. [7.21]