The nitric oxide combines with oxygen preventing the haemoglobin in the blood from doing the same (similar effect to carbon monoxide) - that is why it can be fatal in a confined are and why the NHS can't use pressurised FW aircraft for ECMO transfers. A Sea King is hardly airtight and as such is a perfectly safe, if noisy and slow, mode of transport for the team and the kit.
Wiretensioner - so Crabbette's posts were civilised and gentlemanly (or ladylike) then?
Max - no, it would appear that it had not even popped above the radar horizon of the IPT, much to the annoyance of the wheels here. And whilst you can fill a civvy aircraft with troops, you are going to need some contingency plans to fit weapons (hard points, mountings, pintles etc) which needs to be thought about before the event not after.