Abstract: There is provided is a blower installed at a manhole opening, with which it is possible to facilitate an entry or an exit of a worker or an import or an export of an article. The present invention provides a ventilation system in a pipe conduit using the blower. Provided is a blower comprising: a ring-like or circular arc-like frame; a nozzle installed continuously or discontinuously along the frame; and compressed air supplying means for supplying the nozzle with compressed air, wherein the compressed air supplied from the compressed air supplying means is emitted while swallowing up air in the nozzle or near the nozzle, whereby, an airflow to a normal direction of a disk surface of which the flame is periphery is generated. The nozzle may be a nozzle for exhausting an air flown from an entry port of a cylindrical flow channel to an exit port of the cylindrical flow channel, and a plurality of the nozzles may be discontinuously installed along the frame.