PURPOSE: To enhance the ventilating capacity of a converging duct for an indoor ventilation, by using a curved part having a diameter which is arcuately enlarged at a constant rate for a right angle bent part which extends from a connecting part of a second duct entering the converging part at a right angle thereto, to a connecting part of an outer layer duct of a two-layered pipe.

CONSTITUTION: A converging pipe in which a first duct 2 for ventilating hot air from a bath room is converged to a second duct 3 for ventilating malodor from a toilet at its intermediate part so as to vent the air outside, incorporates a two layer pipe 4 composed of an outer layer duct 41 and an inner layer duct 42. Further, the converging pipe 1 is the integral combination of an insertion part 14 for horizontally receiving and supporting the first duct 2, a curved pipe part 13 fitted thereonto with one end of the second duct 3 and curved up to a horizontal direction so that the direct extension of the first duct 2 serves as an inner duct 42. The curved pipe part 13 is curved while its diameter is gradually increased at a constant rate, thereby it is possible to decrease the internal resistance of the pipe.