McIlvaine (1992) describes the use of ceiling-to-floor air flow.
This vertical down flow design usually has the capability of providing the greatest control for the entire clean working environment, because airborne contamination generated by personnel or specific operations is immediately carried down and out of the room. This design may be varied such that the blowers and HEPA filters are remotely located and the filtered air is ducted to the top of the room and enters the room through a diffusion ceiling arrangement. This variation may reduce cost, the area of filter bank required greater motor/blower capacity and greater attention to leak proof duct joints.
