A warehouse is used to store liquefied petroleum gas (LPG) canisters. If the some of the canisters leak at a total rate of 10 cfm, the ventilation conditions are fair to poor (k factor = 5), and the warehouse is 1,000 ft x 400 ft x 50 ft, What amount of air flow is necessary to dilute the level of LPG to its TLV (1000 ppm) ? How many air changes per hours is this?