Yes, but as Opensauce says ... they do no good! They absorb moisture from the air in the same way as they would if you put them outside your back door.
The air in your van will be at the same humidity as the air outside it (pretty well) ... so the minute you attempt to change that, by absorbing H2O from the air, in comes more outside air to replace it.
Unless ... as OP stated, you manage to hermetically seal the entire van ... which is probably impossible.
as always some great advice there from some meteorological experts and those with unfeasibly dry caravans. i guess their tow cars tow like the caravan isnt there as well?
if the moisture traps absorbed nothing then perhaps they didnt work. those left in my caravan collect about 50Ml in each a fortnight and this is just from the ambient moisture in the air. when i dried out my previous Bailey, with an electric dehumidifier i did block all of the vents to prevent the replacment of the dried air with humid air. my current caravan does not have any damp problems right now (checked everywhere with a damp meter) but the moisture traps still absorb moisture from the air. the probelm is that with the rapid changes in temperature as we have in the UK, one day its -3c the next is 12c is that the cold surfaces condense the moisture thats in the air. same thing happens in my garage, i can go out there after a cold night and the metalic parts of my motorbikes will be soaked with condensation, and theres plenty of adventicious ventilation in my garage. how can you stop that if you cant keep the heater on in your caravan 24/7?
some scoff and say they are a waste of money but they dont cost much so cant actually do any harm.
------------- First van bailey ranger 550/6
Now the proud owner of a coachman amara
They are a waste of money in my opinion but do no harm for those that find comfort in them. Certainly they do collect moisture but that is immediately replace from outside and anyone who thinks stuffing up vents will stop ingress of moist air is mistaken.
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Topic: Moisture traps in caravans?
