Even though one of these was damaged, I still use it for absorbing any moisture that might invade the interior of our safe.  Hydrosorbent SG40 is a simple aluminum holder filled with  Silica Gel and it works.  I keep one in the safe and the other elsewhere.  When the one in the safe is full or close to full with moisture, I remove it and replace it with the backup.  In an effort to maintain even moisture I simply change the canisters about one time a month or no longer than every 6 weeks.