Aerosol generating device

A method for an aerosol-generating device wherein the device comprises a heating device for heating an aerosol substrate, a power source, a first switching element for controlling the supply of power from the power source to the heating device, and a second switching element for decoupling the heating device from the power source, the heating device, the first switching element and the second switching element are arranged in series between terminals of the power supply. The method includes detecting a fault in the apparatus by: controlling one of the first switching element and the second switching element to be on and the other of the first switching element and the second switching element to be off during a first time period; and determining whether at least one observable event occurs during the first time period, the at least one observable event indicating that an amount of power is delivered to the heating device. If it is determined that the at least one observable event occurs during the first time