In theory, you could have trapped moisture in a newly-built system from atmospheric humidity, but possibly not enough to cause a problem?

I would definitely like to find a way to prevent regulators icing up without contravening the rules. We had a regulator (not welding type but aluminium bodied one with sliding components) lock in the fully open position making our system pressure rise. On that occasion, oxide build-up on the inside due to a long period of disuse was a factor, but locking up due to differential contraction and lubricant thickening at the low temperature could still be a concern. Maybe the answer would be a large heatsink or a finned regulator body.