A device to adjust an amount of an active substance inhaled by a user includes two tanks. A first tank includes a liquid having a lower density of active substance than a liquid in the second tank. Each liquid is configured to evaporate when the liquid is heated beyond a predefined temperature limit. An inhaler to inhale the liquid vapor evaporating from each tank by the user. One heating resistor is associated with each tank. A controller to control the heating of each resistor to actuate each resistor independently in accordance with the determined amount of active substance to be vaporized. The ratio of the heating of the resistor of the second tank to the heating of the resistor of the first tank is an increasing function of the determined amount of active substance to be vaporized.