Hi, I have used the moisture absorption trays/traps and crystals available from Wilkos, Robert Dyas etc and they work very well in my workshop which is electrically heated so no moisture from that. The moisture in a well sealed shop is from your breathe blow lamps and carrying in water on a wet day surprising how much moisture they collect. We also used to put them in a narrowboat we had over the winter but they did not collect much which I think was due to the boat being colder.
David