I used the light bulb idea in my wall locker in Viet Nam to keep mildew off of clothing & equipment, and rust off of guns. Here (PA) I use a quart-size silica-gel unit from Brownell's in the safe, and cover all steel surfaces of my guns with Birchwood-Casey SHEATH.I started using this SHEATH about 1963, and have used it ever since.This stuff kept my guns from rusting for three years in Alaska, including time spent on the coast where you have salt spray in the air and constant rain/fog, and never had a rust problem with guns that had an ordinary blue finish. Those silicon impregnated Gun Socks that you can get at Walmart will also keep rust off a gun inside it. But it takes a couple of minutes to put one on and take it off, especially if you have a scope on the gun!