Citadel overpressure matured with nuclear and chemical defence

When did warships begin using overpressurized citadels against chemical and nuclear threats?

The concept was explored before the Second World War but came into its own after nuclear weapons and nerve agents encouraged sealed bridges and protected command centres.

The idea of an overpressurized citadel existed before the Second World War, but it became much more important after nuclear and nerve-agent threats entered naval planning. Positive internal pressure helps keep radiation-bearing particles and chemical agents outside a sealed ship. The arrangement becomes practical alongside enclosed bridges and internal command-control centres. It is therefore part of a broader transition toward fighting the ship from protected spaces rather than an isolated ventilation feature.