atmospheric problems on asteroid cities

The question came up while I was reading Thatotherguy's writeup of Dragon 
Rock:

Imagine a typical asteroid city like Bral or Dragon Rock. There is a 
source of water (be it a portal to the elemantal plane of water, a 
decanter of endless water or whatever), but no precipitation. Also, there 
is not much wind or no wind at all.

How does the atmosphere clean itself? Without rain, dust and sooty 
particles (from smithies or hearthfires) will float around, constantly 
deteriorating the air envelope. 

Everything landing outside the asteroids surface will sink down to the 
level of the gravity plane and be eventually driven out of the air 
envelope. But even when there are enough plants growing to replenish the 
oxygen, there is still a lot of dirt landing on the streets (where it will 
kicked up again by the boots of pedestrians) and on the roofs (where it 
will accumulate).

So my question is: 
Is there some way, be it mundane or magical, to get rid of the "dust-
problem"? Or do I overlook something and the problem doesn't come up in 
the first place?

Tauster