Diffuser of an active liquid agent, for the treatment of a fluid environment, be it at the gaseous or liquid state, of the type comprising a container (1) of the active agent, closed by grid means apt to maintain in position said active agent and to allow the emanation of fluids of the same, said grid means being covered by a barrier film, peelable at the time of the first use to make operative said grid means, wherein said container (1) is closed by a single multilayer film (2, 3a, 3b) comprising at least one external barrier layer (3a) and at least another inner sealing layer (2) apt to maintain in position said active agent and to form said grid means, at the time of the first use of the container, following the simultaneous removal of said barrier film and of predefined portions (4) of said sealing layer (2).
