Composite pressure vessel for hydrogen storage

A composite pressure vessel comprising an inner normally gas impermeable liner that becomes gas permeable at a predetermined temperature, a load bearing intermediate layer configured to withstand the internal pressure exerted by the compressed gas to be stored in the vessel, and a thermally protective outer layer formed from a material having a lower thermal conductivity than the intermediate layer, whereby the thermally protective outer layer has a greater temperature gradient across its thickness than the intermediate layer when the vessel is exposed to fire.