The present invention is not in any way limited to the above embodiment. Further, an embodiment with part of the above configuration omitted while it remains capable of solving the problem is also included in the embodiment of the present invention. Further, an embodiment configured by combining a plurality of the above embodiments as appropriate is also included in the embodiment of the present invention. Any embodiment which could be made without departing from the spirit of the invention as defined solely by the terms in the appended claims is included in the embodiment of the present invention. Although references used in the description of the above embodiment are also used in the appended claims for ease of understanding, it is not intended to limit the technical scope of the invention defined by the appended claims.

For example, in the above embodiment, the artificial air aperture 30 can be positioned in any arrangement, and may be, for example, an array arrangement aligned vertically and horizontally as shown in FIG. 4(e). With this arrangement, since the surface area of the ventilation port 40 can be increased, a fluid outside the casing 10 can be efficiently introduced into the casing.