Air duct connection box having multiple connection points

Connection equipment 10 into an air duct comprises a connecting box 11 to which a ventilation terminal device, such as a supply air terminal device or an exhaust air device, can be connected. The connecting box 11 comprises walls 11a1, 11a2-11a6, which bound an air chamber, and at least two optional connection points B1, B2 from which the connecting box 11 can be connected to an air duct. In a method for using the connecting box 11, a connection point is chosen for the air duct R into the connecting box at the place of installation of the air terminal from the optional connection points B1, B2 by providing the connecting box 11 from a chosen direction with a coupling sleeve 13 having a tube part 13b to which the air duct R is connected. The optional connection points may comprise a weakened area 15 along which a part 14 bounded by the weakened area may be removed. Covering plates 12 may be placed over unused connection points.