This unit incorporates a refrigeration system that dramatically increases the operational range of the cabinet. A low-pressure water vapor generator, injecting saturated water vapor into the recirculating air duct, controls chamber humidification. This is preferable to steam generation because steam introduces additional heat to the chamber atmosphere. This process can then compromise temperature control. Uniform temperature and humidity are maintained by circulating chamber atmosphere through a recirculating air duct system. The air ducts also serve as shelf supports and can be easily removed for cleaning. NextDayScience's Humidity Test Cabinets provide a controlled environmental chamber for a wide range of industrial and biotechnical testing applications.