Boveda

Boveda’s patented 2-way humidity control continually responds to ambient conditions by adding or removing moisture to affect the enclosed environment and deliver the pre-determined RH (relative humidity) level printed on the pack.
When do I know when they need to be replaced? All Boveda will turn into a solid wafer when they’re dead. So it’s short of that, when there aren’t many soft spots left, that you’ll want to replace them. Pronounced crystallization and hardening of the corners first is completely normal.