You are in an old spy movie, and have been locked into a small room (volume 1,000 ft3 ). You suddenly realize that a poison gas has just started entering the room through a ventilation duct. Recognizing the type of poison from its smell, you know that if the gas reaches a concentration of 100 mg m-3, you will die instantly, but that you are safe as long as the concentration is less than 100 mg m-3. If the ventilation air flow rate in the room is 100 ft3 min-1 and the incoming gas concentration is 200 mg m-3 , how long do you have to escape?