Hi Mike,
20 years experience in the field and never used a moth ball yet!and this is as ludicrous a cure for mice as I have ever heard! It's rather like the ultra sonic gadgets that they sell and promise that they keep rodents away- THEY DON'T - so don't waste your money! There is an in built survival instinct in these creatures as there is in us and they very quickly become used to the new smell, noise or whatever and put up with it. And anyway even if it were true can you imagine the amount of mothballs you would need to make life unpleasant for a mouse? I wouldn't want to go in that caravan would you?.Talk about eyes watering eh? I keep my caravan baited at all times when in storage and back these up with good quality trap/s(SNAP E's)in each lower compartment with high protein food on it ie peanut butter and this will, 99 times out of a hundred, deal with this destructive pest. As a help,if you are not visiting the van for some time it is probably best to place them on polythene for obvious reasons. I don't get problems now and I havn't had a mouse in for years ( no evidence of droppings gnawing etc) but I will never be without protection. I did get one in many years ago- chewed cushions, curtains etc and it was my first caravan- I was gutted. NEVER AGAIN. The next one didn't see the next day!! Hope this helps. www.acclaimpest.co.uk.