This project is an emergency renovation of BHSF Bethesda West Hospital to provide temporary COVID-19 treatment rooms for use during the current outbreak. The scope of this project includes part of the second-floor Post-Operation day bed area and the 4th and 5th floor patient wings. The design methodologies are detailed below for each area of the renovations. Second Floor The second-floor Post-Operation day bed suite (served by AHU-1 located in a 3rd floor mechanical room) will be converted into a temporary COVID-19 treatment area with a temporary anteroom as detailed on the Design Documents. An existing smoke rated wall extending to the deck above will serve as a physical separation between the COVID-19 treatment area and the rest of the hospital. The entire suite is being converted to one-pass air and balanced to be negative with respect to the Anteroom and the rest of the hospital. The mechanical systems have been modified to accomplish proper isolation as follows. The return ductwork serving the emergency COVID-19 treatment area was converted into exhaust by temporarily ducting the existing return to an abandoned duct routed to the 3rd floor mechanical room and capping the associated return connection to AHU-1. This duct was routed to the 3rd floor mechanical room and will be exhausted using a temporary, field constructed HEPA filter box and a temporary exhaust fan. This fan will discharge the COVID-19 area exhaust safely to the building exterior on the side of the building opposite the outdoor air intakes. The temporary exhaust fans are sized and have been balanced to provide negative pressurization between the COVID-19 treatment area and the temporary Anteroom and negative pressurization between the temporary Anteroom and the rest of the hospital. The AHU was designed with additional capacity for future expansions. The outdoor air volume is being increased to ensure proper air balance. Return ductwork serving spaces outside of the COVID-19 treatment area are being temporarily ducted to AHU-1 so that the AHU can continue normal supply and return operations in these spaces. 4th and 5th Floors The 4th and 5th floor patient rooms (all served by AHU-6 located in a 3rd floor mechanical room) will be converted into temporary COVID-19 treatment rooms. The existing patient rooms have perimeter smoke rated walls which will provide a physical separation between the COVID-19 treatment rooms and the common areas. The treatment rooms are being converted to one-pass air and balanced to be negative with respect to the corridors. The mechanical systems have been modified to accomplish proper isolation as follows. The existing return ductwork serving the 4th and 5th floors have been converted to exhaust by temporarily ducting the return main to field constructed HEPA filter boxes and temporary exhaust fans located in the 3rd floor mechanical room. These fans will discharge the COVID-19 treatment room exhaust safely to the building exterior on the side of the building opposite the outdoor air intakes. The existing return grilles not serving COVID-19 treatment rooms have been blanked off to provide additional positive pressure from the clean spaces to the COVID-19 treatment rooms. The temporary exhaust fans are sized and are balanced to provide a negative pressurization of 0.01” w.c. between the COVID-19 treatment rooms and corridors.