Atmospheric wind effects on depressurization for indoor asbestos pollution containment: experimental analysis and a ventilation network model validation

Hazardous pollutant containment zones in buildings should be depressurized by a dedicated mechanical ventilation system to prevent pollutants from escaping from the indoor to the outdoor atmosphere. Depressurization can be affected by atmospheric wind conditions, which can cause a momentary breach. The goal of this study is to analyze the effect of wind velocity and direction on depressurization and potential containment breaches and to validate a ventilation network model for indoor pressure and breach prediction. Wind-tunnel (WT) tests are performed on a reduced-scale isolated building model equipped with a properly downscaled mechanical ventilation system. The time series of the external pressures (pe ) on the building surfaces and the indoor pressure (pi ) are measured simultaneously. As an alternative approach, a ventilation network model is designed that uses the pe data from the WT tests to determine pi . The network model is then validated by comparing the pi and breach occurrence results by the WT tests versus those by the network model. It is shown that although negative pi can be maintained continuously, containment breaches occur locally where and when pe exceeds pi . The breach probability depends strongly on both wind speed and direction. The network model is successfully validated, where the deviation in breach prediction by the network model is less than 10% compared to the results from WT data alone. The results also show that a -20 Pa depressurization may not be sufficient to avoid a containment breach, which stresses the importance of this and future research on this topic.