The invention relates to a unit (130) referred to as an anti-condensation unit, comprising means to be connected to a diffusion head (120) able to produce a cloud of a nebulized product that is to be diffused, which unit comprises: a. a duct (131, 132) comprising an inlet (122) for a cloud of nebulized product; b. at one end, referred to as the diffusion end, of said duct, an outlet orifice; c. at the other end (134), referred to as the intake end, of said duct, means (140) for generating a flow of air between said end and the diffusion end of the duct; d. an internal surface of said duct extending in a direction perpendicular to the direction of the air flow so as to create an obstacle in the path of said flow in the duct; e. retention means for retaining the nebulized product halted by said internal surface. The invention also relates to a device for diffusing a product implementing such a unit and to a method for diffusing a product using such a device.