A thermal vaporizer for a liquid formulation comprising a volatile active, a container for said vaporizer and a thermal vaporizer assembly. The vaporizer (A) comprises a housing (1) having a heater unit (2) for evaporating the liquid formulation, a mounting (8) for a container (50) for the liquid formulation, a passage (5) for a wick means (52) to be heated by the heater unit (2), at least one outlet (6) for evaporated volatile active and an electrical contact connected to said heater unit (2). The vaporizer selectively operates the heater unit at, at least, two different predetermined heating temperatures, such that the heater unit is selectively activated by the container (50).