Thanks everyone for your thoughts both scientific and anecdotal.
I suppose with hindsight, I should have recognised that I never get rusty tools in the garage which is effectively part of the house with cavity wall insulation and a room above it.
There is just the slightest gap around the door which I guess helps with the ventilation and I have a modern condensing central heating boiler in there which, whilst well insulated, must give some heat into the garage.
I had to put the car away soaking wet the other day and I noticed that the Mohair hood did dry out completely within 2 - 3 days.
So for the time being I'll spend my money on something else for Mog and I'll use my chisels like taking budgies down the mines in the old days.
If my best wood chisels don't rust (without being oiled) then it can't be too damp.
Last edited by IvorMog; 01/02/19 05:27 PM.