US Patent 7753977 Air filtration system having a removable diffuser

An air filtration system includes a support structure, an enclosure coupled to the support structure and including an air outlet, a filter and a fan operatively coupled to the enclosure, and a diffusion screen configured to cover the air outlet. The diffusion screen includes a screen frame configured to be removably attachable to the enclosure with at least one releasable fastener, and at least a diffusion layer substantially spanning the screen frame to cover the air outlet to provide unidirectional or laminar air flow from the air outlet.