Abstract: A modular air circulation and filtration unit, which can be conveniently installed in any conventional drop ceiling, as well as, other types of ceilings is disclosed. The circulation and filtration unit includes a housing, an electric rotary blade fan assembly, and one or more air filters. The sealed housing is shaped and dimensioned to approximate the panel space of a conventional drop ceiling or the joist spacing of conventional joist ceilings. The housing can also be modified to mount directly to the ceiling sheathing. The housing includes a flat base and an arcuate top which enclose the fan and filters. The housing also includes a hinged outlet vent and one or more hinged inlet vents, which support and provide access to the air filters. The fan assembly is mounted inside the housing interior with one or more fan cowlings isolating the fan blades from the inlet vents.