Air pressure fluctuations of drainage stacks at a high-rise office building

This study examines air pressure variations along a discharging stack with unsteady discharging flow rates, including the fluctuation frequency, the maximum and average pressures with their respective standard deviations at a drainage stack of an in-use office building. With a modified constant, the maximum air pressure at the drainage stack could be described by the probability density function of the measured data using earlier proposed mathematical expressions for steady discharging flow rates. The average prediction and the maximum under-prediction of the absolute peak pressure were determined with the margin of errors taken within certain confidence levels. The results would be useful for understanding the air pressure in drainage stacks and help increase the potential of installing a real-time monitoring system in a high-rise drainage stack.