A vented dryer having a drum to dry damp laundry by warm process air; a first process air duct upstream of the drum; a heater to heat the process air in the first process air duct; a supply air duct leading into the first process air duct; an exhaust air duct; a second process air duct downstream of the drum and transitioning into the exhaust air duct; a blower; a first temperature sensor in the first process air duct; and a heat-buildup generator to generate a heat buildup at the first temperature sensor if a counter-flowing air current occurs.