An air dehumidifier for use in small enclosures such as gun and other types of safes is disclosed. The air dehumidifier provides a natural convection dehumidifier circulation system for use in enclosures that reduces natural convection airflow through a drying chamber and thereby dehumidifies and circulates air within the enclosure. Heated air released through the air flow apertures combine with air drawn in through the air intake apertures in the base, to provide air circulation and dehumidification within the safe interior. This invention also provides a drying chamber end cap which prevents articles within the enclosure from blocking the airflow out of the drying chamber.