pipeline 30 on an outlet side of the exhaust control valve 32 the tumble dryer of the present invention is to change the drying chamber to a low pressure or vacuum condition by drawing air out so that air moisture can be fully drawn away from the drying chamber subject to the physical principle that fluid can be evaporated easily under low pressure actually as shown in fig1 outside air can flow through the intake pipeline 20 the intake lint screen 21 and the intake air control valve 22 into the drying chamber 12 and then the heater 13 is operated to heat the washing and or object in the tumbler 15 causing the water content in washing to be vaporized into air vapor that is then carried away from the drying chamber 12 to the atmosphere through the exhaust lint screen 31 and the exhaust control valve 32 fig2 shows a tumble dryer in accordance with a second embodiment of the present invention according to this second embodiment a pre heater 50 is mounted on the outside of the housing 10 and adapted for heating intake air so that pre heated warm air flows through the intake pipeline 20 and the intake lint screen 21 and the intake air.