He gives it just another second to make sure the beast is also disoriented by the dust before taking off after her. Normally he wouldn't run. He'd rather fight it head on and see who comes out the victor. But unfortunately he has learned that this isn't a solo mission after having been on the train long enough. SO he knows he has to make sure his team mate survives this.

So he follows, gaining on her easily. He isn't worried about his breath. His body will be effected by the poison but it won't be as harshly as someone who isn't used to such things. So he holds his breath but takes a moment to bring his sleeve up to his nose to breath slightly filtered air through the fabric.

He reaches out and scoops her up under one arm, reaching out to cover her face with his sleeve as he carries her further and faster. "Slow shallow breath."