Plot hole: After Frank and Freddie accidentally release the trioxin gas, there are several shots of the gas entering a return air vent and traveling through the heating, ventilation and air conditioning system belonging to the warehouse. Finally the gas exits into the freezer directly on to a hanging cadaver. This room was previously confirmed as a freezer and would have had its own self contained refrigeration system with its own ventilation system. Typical freezer doors also seal as they close. The cadaver would have never come into contact with the trioxin gas and would have never reanimated.