The invention relates to a device for evaporating volatile substances, which includes a heat source (5) that evaporates volatile substances from a refill (2), a heat detector (4), which can detect the heat from said heat source (5), and indicating means (7) connected to said heat detector (4), which emit an indication when the heat detector (4) detects the heat from said heat source (5), and is characterised in that said heat detector (4) is placed above said heat source (5). The invention allows the indicating means to activate practically simultaneously with the placement of the heat emitter.
