Abstract: A work space for removing hazardous materials within an occupied building is made safe both for the workers working within the work space and others outside the work space by defining a decontamination space having a plurality of rooms and air locks between the rooms and a work space opening on the decontamination space, supplying fresh air to the work space through a duct in the wall of the work space, supplying fresh air to each of the rooms and air locks and evacuating air from each of the rooms and the air locks and forcing the evacuated air through the same work space wall to provide a substantially laminar air flow from the wall. A row of air filtration devices normal to the air flow filters the air flow and expels the air in the same direction away from the wall. A second row of air filtration devices receives the previously filtered air, further filters it, and expels it into a duct leading to the outside of the building.