Civilian: What should I do if I were in a ＿＿（47）＿＿ ? Fireman: You had better cover your mouth and nose with a ＿＿（48）＿＿ . Take the nearest ＿＿（49）＿＿ right away. ＿＿（50）＿＿ immediately.