Ah, refuse pile sorted. Put it outside, no miasmas.
On the other hand, it's a rather nice trap if you make massive areas of refuse underground, make sure your dwarves go nowhere near it and then just watch as beasties are, I think, killed by miasmas.
How do you set a dwarf to be, say, a miner? I've only got one guy mining out a 50x50 cavern and it's taking forever.