What is this strange dust ?

allielloyd

Hi,

apologies if this doesnt work (was hoping to post a pic) but Im new to caravaning and have just bought an old 'project' Lunar.  Having a poke around in it now I've noticed a strange, fibrous sort of dust behind
the door frame seals.  sort of like wood shavings, but soft and more grey than brown.

Any ideas what it could be please ?

Thanks