A method producing a gas flow containing an essential oil vapor includes the following steps: creation of a pressurized gas flow with a controlled flow-rate and a given temperature; and injection into the pressurized gas flow of a liquid composition including at least one liquid essential oil, at a dosed flow rate; whereby the flow rate of the gas flow and that of the liquid composition are controlled such that the gas flow, following injection, has a partial essential oil vapor pressure of at least 20% below the saturation pressure of the essential oil vapor at the temperature of the gas flow.