The invention includes: • - an evaporation device (7) comprising a gas-circulation pipe (9), and a material having large specific surface area (11) filling an evaporation section (13) of the circulation pipe (9)； • - a device (15) for circulating gas through the circulation pipe (9)； • - a liquid impregnating the material having large specific surface area (11), the liquid containing at least one product or a mixture of volatile biocidal and/or plant-protection products, with a boiling temperature of 130 to 280°C, the material having large specific surface area having a liquid retention capacity of more than 50 L/m of material having large specific surface area at 20°C； • - a refilling device (17), arranged to reimpregnate the material having large specific surface area (11) with liquid or to replace the depleted material having large specific surface area (11) with a novel material having large specific surface area (11) impregnated with liquid.
