Hi all,

we live on the ground floor of a two storey apartment block.

The apartment is brick and render on the outside.

Recently, in one corner of the floor I have discovered some dark dusty
particles appearing along the skirting board.

When I wipe with my finger, it seems to disappear, like dust. Because this
wall (that corner of the room) faces the outside world, could it be damp -
is this dust consistent with that?

If so, what do we need to do to get rid of it or are we destined to it
forever?

(It has rained a bit recently, could that be it? Just moisture? Open some
windows?)

Or is it something else? Replies are apprecaited.