This study evaluated the effectiveness of expedient sheltering in place in commercial buildings for protection against airborne hazards, as described in U.S. Government guidance to the public. Expedient sheltering measures (plastic sheeting and duct tape) were applied to four different rooms inside commercial buildings. In two rooms, additional tests were performed with ceilings covered, and one room was tested with persons entering and exiting the shelter. Measured air exchange rates for the shelter rooms and literature values for air exchange rates for large buildings were used to determine protection factors for various scenarios. Protection factors were compared for leaky, typical, and tight buildings and shelters under various occupancy times and plume pass-over times for hazardous airborne contaminants. Protection factors ranged from 1.0 to 3960, depending on the conditions. Results reinforced the importance of timing for effective sheltering in place. Sheltering in place can be most beneficial if people enter shelters before the arrival of a hazardous plume and people exit shelters as soon as the plume passes over. However, sheltering in place can be detrimental if people enter or exit shelters too late. CO2 and O2 concentrations were calculated for a tight shelter with maximum recommended occupancy.
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