Abstract: In a method of constructing a ceiling frame to support a filter at the ceiling of a clean room, the method is characterized in that a number of divisional frame units are formed, each in a rectangular frame, to frame a filter unit to be installed, that those divisional frame units are positioned one after another at the ceiling of the clean room, that the ceiling frame is formed by connecting, to unify, abutting frame members of the divisional frame units, and that the divisional frame units are hanged at the ceiling with hangers applied at the abutting portions of the divisional frame units.

Abstract: A clean room arrangement comprises a clean room having an upper portion and a lower portion. Clean air is introduced into the upper portion of the clean room, flows downward and expelled from the lower portion of the clean room. An air recirculation passage is connected to the clean room such that the lower portion of the clean room is communicated with the upper portion of the clean room. A heat source is provided in the air recirculation passage to generate an ascending flow of air in the air recirculation passage so that the air descends in the clean room due to natural convection.