Abstract: An air handling unit that includes a main support member and front, rear and top covers mounted on said support that forms a housing for enclosing said unit. The covers have side walls that close over the support frame in abutting contact to form an interlocking seam therebetween at closure. Ribs are mounted upon the side walls of the support frame which bias the side walls of the covers outwardly to render the seam relatively air tight at closure. Two covers are securely affixed to the main support member while the other is removably attached to the main support member by a latching means. A HEPA filter is mounted in the main support member along with a blower system for drawing air through said housing.