A dispensing device includes first and second actuators that actuate first and second containers, respectively, to dispense volatile material therefrom and a sensor for detecting an environmental condition. In a first period the first and second actuators are inactive, in a second period the first actuator actuates the first container at a first frequency to dispense volatile material therefrom, and in a third period the second actuator actuates the second container at a second frequency to dispense volatile material therefrom. If the sensor has detected the environmental condition, the first and/or second actuators actuate the first and/or second containers, respectively, during a fourth period at a third frequency.