Such apparatuses are used for discharging active substances along with various carrier media, water often being used as a carrier medium. In order to ensure that the water perfectly nebulizes together with the active substance, the mist pipe (10) comprises at least three additional pipes (3 to 6) which partly surround each other to form annular chambers (31 to 33). Such a mist pipe (10) allows the size distribution of the drops to be kept within narrow limits even when water is used as a carrier medium. The nebulizer and the mist pipe (10) are mainly used in the health sector, in agriculture, plantations and greenhouses, for protecting supplies and for disinfection purposes on humans, in animal husbandry, and in food production.