Yes, didn’t work....do the math...the dehumidifier rod is a heater, does not move air...may raise the temp a couple of degrees in a walk in closet. A 100 watt light bulb will generate more heat than my 40 watt golden rod...

Why do you ask?

What does this have to do with guns?

The simplest solution is to design the closet properly from the beginning, with HVAC outlets and returns.

The closet should indeed have adequate heating/ventilation/air conditioning based on the volume. That would include one or more HVAC supplies, but not returns--which are not permitted in closets per the International Residential Code and which forms the core of most statewide building codes. Installing a Goldenrod heater (as shown) which is designed for small volume gun safes in a closet of larger volume will be very much inadequate.