I know they work... just not for me.
My father has about a dozen of these. He uses 2 in his (massive) gun safe, and the rest in his tiny little gun room. He has low humidity in his house, and only has to recharge the desiccants every 2-3 months. With his electric oven, a cook time of about 3.5 hours will recharge 4 cans. While they cool, he bakes 4 more cans; and repeats the cycle until everything is dry, cool, and back protecting firearms and reloading equipment. The cans are a little flimsy, and they're covered in crush silica, out of the package. But, they're otherwise of reasonable quality. I, personally, have two of these - one each for two "18 gun" safes. Combined with a golden rod in each safe, they keep my firearms from rusting. However, these desiccants are nearly impossible for me to "recharge" (dry out). Between the moderate humidity in my house, and the "new" natural gas mixture used to fuel my stove, these just never turn completely yellow (indicating that they're 'recharged'). Instead, I get about 1 inch of yellow beads around the circumference of the canister, with the core still dark blue. I can bake them for 8 hours, plus, and it never changes. The core never dries out. I don't know if it is a fault with the silica gel beads, themselves, or just the natural gas mixture we're stuck with in this area, but I can't get these fully recharged. As such, the useful time period for them to be in my safes is about 1/3 of that quoted by the manufacturer. So... Beware. If you have a natural gas oven and use the "new" gas mixture in your area, you may have issues. -- The "new" mix mandated by the EPA (and loved by gas companies, because it requires less refining) has many more contaminants and significantly higher moisture content than we got in the past. It's a pain in the back side, but you WILL have to deal with it at some point, if you use natural gas in your home. I would recommend these to a friend, only if they have an electric oven.
