[voice]
I don't really know the powers and abilities of others within the dome. I think that myself and Oniisama would be able to be out for a time. It wouldn't kill us, and we don't really become sick...any attempts to keep the toxic air away from us would be workable but only temporary before growing too tired.
I can't imagine it would be wise to remain exposed to something like that for long periods of time anyway. Anyone who could...possibly put up a barrier, or have some form of control over the elements, maybe?