Abstract: An air shower for a clean room system, having an assembly and knockdown architecture. The assembly and knockdown architecture means an air shower is formed from a plurality of elementary components with standard specification in size. The air shower primarily comprises two main cases, one top case and one bottom case. The top and bottom cases are two rectangular parallelepipeds. Each parallelepiped consists of two right triangle cases and one isosceles triangle case. By means of the arrangement of these two top and bottom cases, an air shower can be formed with octagon shape or tunnel type. This gives the number of people stepping into or getting out of an air shower more flexibility, and increasing or decreasing the number of the installed devices can be dependent of the volume of the business. Meanwhile, the configuration of the space for an air shower is adjustable.