Extracted text: 5.5 An atrium in a hotel building is 20 m high and has a floor area of 600 m2. The atrium has relatively large openings at the floor level (-10 m2). An elevator door, which is 15 m above the floor, has a leakage area of 0.06 m2, and smoke can spread from the atrium to the rest of the building, mainly through this leak. If the gas temperature in the atrium is 250°C and the ambient temperature is 20°C, calculate the mass flow rate through the elevator door. Suggested answer: Assuming the pressure difference across the lower opening to be -0, the pressure difference at 15 m height causes m 0.43 kg/s.