Equipment must be suitable for it's location- and that, of course, isn't always clear.
Thinking back, it seems to me that every freezer/ walk-in that I've been in has shared a few construction details.
While the boxes near the fan were of the "usual" type, the light switch, when inside the unit, has been of the lever-operated weatherproof type. I think that this is am attempt to comply with NEMA standards for equipment that will operate even where there is external icing (Is that Nema-3S?)
Lights have always been enclosed- either incandescents inside "jelly jars" or fluorescent tubes inside plastic sleeves.
Wiring has always either been pipe or MC.
I can't say any of this is "required," but it does seem to be the practice. Where the freezer is used for food, the USDA and the Commerce Department (fish) have a slew of their own regulations as well. I am sure the NSF (National Sanitary Foundation) has a standard that applies.
