"Elli--!" Tonks couldn't finish the other woman's name because another fit of coughing had shaken her to the bone. She tried to help when she saw the vague outline of Elliot go down, but by that time the gas was so thick that she couldn't have reached out and actually find her even though she tried.
Her heart was pounding, attempting to make up for the oxygen lost, but really it did no good. She slumped over in the box, crumpling as she passed out.