My daughter is in a wheelchair and self-regulation of her body temperature is a challenge, so her overnight outing required some special precautions, including a small, heater-equipped trailer. Conditions were far from optimal with the mercury dropping to below freezing at night, but it served up a stark reminder that moisture management applies to more than just your gun safe.
The lesson is common sense. The trailer is small, and the first night my wife and I, along with Sniper-our 150-pound, year-old, black Great Dane-saw temperatures drop to around 28. Inside the little camper/trailer, it was comfortable, but condensation from our breath and cooking collected on the windows and dripped inside. Moisture also collected on my 1911 when I entered after being outside. Cold metal tends to do that when subjected to warm and humid environs.
I wasn't worried about my well-oiled gun as much as I was about our daughter's warmth. If her bed next to the window got wet, it could quickly become dangerous, so I broke out a product called Eva-Dry 500. It's wireless, has an indicating desiccant that turns pink when saturated, and is recharged by simply plugging into a wall outlet for 15 hours or so. I monitored my handgun's slide afterward, and the problem reduced noticeably, but not completely. Bedding didn't get wet the next night when our daughter arrived, either.
I've spoken to one of the co-owners. He travels extensively and uses the company's E-150 Moisture Eliminator Pouches in his carry-gun case to battle this kind of condensation and its potential for rust. The disposable packets are effective for 150 square feet and when the orange indicator turns green, simply toss in the trash.
I put the Eva-Dry 500 through testing identical to that which I subjected both the Liberty Safe Mini-Canister and Drierite. The Eva-Dry products' silica gel is slower working than the others. Relative humidity drops significantly and reliably, even after multiple recharges, but instead of it taking 72 hours to come to equilibrium in the airtight canister, it takes two weeks.
In the trailer for two nights, the slower action was somewhat of a disadvantage, however, in a rarely opened gun safe or a case protecting a wood-stocked hunting rifle in a cold-weather destination, that slower, methodical action is probably a desirable trait.