damp?

Humid atmosphere in un used c/van.general damp feel. Buckling ceiling ingress of water
Black mould on walls damp maybe leak.
Ensure none of the air vents are blocked/obstructed
Free flow required and essential in use.

Your not specific where so assume everywhere.
check all external beading sealing putty apply mastic bead where suspect. First clean off all beading sticking out up on edges and clean the edge ready for new beading make sure it reall dry/.
mastic ALL the beading where you see sealing putty including the awning rail. External mastic white Wickes or other DIY shop and gun of course.
Do not cut the dispensing tube tip leave it and apply mastic in two to three layers pressing in against the ally bead strip so mastic finds those missed holes then two more coats with less pressure.

If not ingress leak just dampish and smell of damp if you have access to electric then think dehumidifier. or even silica jell packs.

Nobby
January 2009