A hazardous apparatus, such as a microwave oven includes a power cut-off safety switch (300) which automatically cuts off the supply of electric power to the apparatus if a housing panel (400) is removed while the electric power supply cord (100) is still plugged in. The switch (300) is engaged by an extension (420) of the housing panel (400) which extends through a slot (510; 510a) formed in another housing panel (500). The slot can be other than straight in order to resist efforts to insert objects therethrough.