Why do safes or gun safes get humid?

The place where a safe or gun cabinet is placed has a great impact on humidity.

For example, safes or gun safes that are placed in basements, garages, or located in high humidity areas (such as Malaysia, Singapore, and Northeast Canada) are prone to humidity.

Due to the high overall humidity of the air in the location, when they are opened and closed, water molecules will inevitably enter their interior, which, combined with the lack of air circulation inside after closing and the change in temperature between day and night, can easily cause water molecules to condense and make the interior humid.

Especially for long-term storage items, during which they are rarely opened, the problem of moisture is more prominent.