When using the "System ID" tool to number pipes (I assume also for ducts), the ID can automatically be incremented. The starting value is "001", which made me believe the tool would be smart enough to remove the leading zeros as soon as the second digit comes into play, in other words go from "009" to "010". Apparently it doesn't, resulting in "0010" instead which makes alphabetical sorting a mess.

Support confirmed this and filed Enhancement Request 1104311. Please vote for this idea/submit SR with reference to the ER if you agree this should be changed.