I know Culdians do not hold with the doctrine of doomsday and the last trumpet, but do they recognize that there may be a doomsday brought about by nuclear warfare, chemical or biological warfare, economic collapse pure accident?

The Culdian attitude is that while everything should be done to prevent any of the eventualities you mention, it is prudent to be prepared for any emergency on a world scale. The Culdians co-operate with survivalist groups and in fact it was a Culdian who registered the first organization wholly devoted to this problem.