PURPOSE: To make the installation work of a nozzle unit easy by connecting a connection guide to an elbow so as to mount the guide to the inner surface of a wall and connecting a nozzle adjuster to the guide and mounting a nozzle cover by means of a cover mounting frame after having mounted the nozzle thereto.

CONSTITUTION: A nozzle connection guide is fixed with an elbow 40 and a nozzle unit mounting hole 40' of a wall 40 while a nozzle adjuster 29 is mounted to the front of the nozzle connection guide. A connection unit of a nozzle 32 is screwed into a nozzle receiving port of a nozzle adjuster 29 so that the nozzle 32 may be mounted to the nozzle adjuster 29, thereby mounting a cover mounting frame 35 to the mounting hole 40' by means of small machine bolts 43. An opening 37 is formed on the front of the cover mounting frame 35 while a nozzle cover 36, which forms a nozzle cover 36 on the bottom, is mounted by means of an engagement unit 38 and a claw 35'. This construction make it possible of install the nozzles easily, and what is more, definitely.