At North Luffenham in the mid 1960's the explosive decompression was from 27,000 feet to 52,000 feet for V Force crews. 27,000 because that was the highest the Vulcan pressurisation let you go and 52,000 because that was the official limit of the pressure breathing system using the Pressure Jerkin. On my squadron we always wore the Partial Pressure Jerkin but not the G Pants (we were never issued with them).
ACW