PURPOSE: To provide low-cost means capable of keeping air conditioned air in a capsule at a high efficiency by a method wherein air is forcibly discharged from a discharging port under operation of a discharging fan to form a circulating advancing air stream directing from the surface communicating with the other terminal of a blowing column toward the discharging port.

CONSTITUTION: When air curtain (b) is blown out from a plurality of blowing- out columns (a) raised in parallel to each other to face in opposite relation, the air curtain (b) has the same direction as that of the rotational direction at a tangential point (g) with each of the phantom rotational columns 1, so that a practical column of circulating air stream is generated by a fluid friction of the air and the circulating air stream is rotated together with air enclosed in the capsule (h). The discharging port (d) and each of the discharging column (a) are connected by a conduit, and the conduit has a discharging fan (k) inserted therein, so the air circulation system is formed by the air curtain (b), air in the capsule (h) and the conduit.