These packets pull moisture from the air and can be used almost anywhere. Each packet is individually wrapped in a foil pouch to prevent the desiccant from activating. Once opened each packet can draw moisture from 5-7 cubic feet for about 6 weeks before it will need to be recharged. Each packet includes a handy moisture indicator to let you know when it is time to recharge. Units can be recharged in a standard, vented oven at 200 degrees for 3 hours and can be recharged 3 or 4 times before its moisture absorbing properties are lost.