Read the excerpt about the effects of poison gas. like some liquid the heavy-coloured vapour poured relentlessly into the trenches, filled them, and passed on. for a few seconds nothing happened; the sweet-smelling stuff merely tickled their nostrils; they failed to realize the danger. then, with inconceivable rapidity, the gas worked, and blind panic spread. —british eyewitness on the western front, 1915 according to the excerpt, how did the poison gas work to kill the soldiers?