A biocidal treatment evaporates a liquid having biocidal properties. An absorption organ has absorbent strips suited to retain the liquid, each absorbent strip having a top first end and a bottom second end, The liquid is injected into the first end of each absorbent strip, the liquid flowing by gravity along the absorbent strip towards the second end, the liquid having biocidal properties being injected at a predetermined flow rate. The liquid is evaporated by producing a gas flow directed towards the absorption organ at a temperature below 50° C.