This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
Double wall construction of metal or high grade plastic. Wood is not
recommended, because it is a fire hazard and is difficult to clean.
Enclosed heating elements.
Counter top design.
An enclosed thermostat from 85F to 160F.
Fan or blower.
Four to 10 open mesh trays made of sturdy lightweight plastic for easy
UL seal of approval.
A dial for regulating temperature.
A timer. Often the completed drying time may occur during the night and a
timer could turn the dehydrator off and prevent scorching.