I got a digital hygrometer for my safe. A simple 40 watt bulb keeps it at 30% and 74.6 degrees. The wonder rod I used to have ended up getting dangerous. The rubber end got so hot it completely melted. So I decided to go with the light bulb a couple years ago. Looks like it's working fine. The light bulbs last about six months and I have enough stored up to keep me going for a several years.