In addition to using HEPA air purifiers to maintain air quality during the demolition of the existing space, we also took a close look at the existing HVAC system.  Inside the space we have existing VAV (variable air volume) boxes.  VAV boxes are used to zone areas in large commercial buildings and also contribute significantly to the efficiency of the HVAC system.  On our existing VAV boxes we added additional filter media to ensure that we were not redistributing dust and other particulates in the air to other areas of the floor space.  We also used box filters and an extra layer of filter media on all return ducts.  This ensures that we were not bringing poluted air back into the HVAC system and redistrubuting the air to other areas of the building where other tenants would be impacted.