This decreases the boiling point of water inside that product and thereby increases the rate of evaporation significantly.
The oven is divided into hollow trays which increases the surface area for heat conduction.
The oven door is locked air tight and is connected to vacuum pump to reduce the pressure.
The dryer door is tightly shut and steam is passed through the space between trays and jacket so that the heat transfer occurs by conduction.
[4][non-primary source needed] Vacuum dryer can be used to dry heat sensitive hygroscopic and toxic materials.