I put the E-500 and a humidity meter in my safe. After 24 hours, there was no change in the humidity level. I recharged the E-500 for 15 hours and returned it to the safe. After another 24 hours, there was no change in the humidity reading. I took the E-500 out of the safe and put in one of the rod dehumidifers that works by warming the air. After only a few hours the humidity dropped 4%. I believe that while the E-500 does capture moisture, it is grossly undersized for this task.