I run a 25 or 40w incandescent bulb in the current safe, got one of those wardrobe heater tube thingies for the new safe I'm building.
I've seen guys running strip LEDs in their safes, not for any attempt at heat but just so they can see where everything is
Musicians have a similar problem, I've heard of people running a bulb inside a piano before - all those steel strings and whatnot would want to rust if they could
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