Here is a picture of the inside of a walk-in cooler. Please note that the pipe is held away from the surface (with mineralacs).
USDA, and most Health Departments, require pipes to be supported in such a manner as to not interfere with cleaning. In practice, this means leaving a pretty good space between the structure and the pipe. You don't want to make a 'pocket' to trap crud.
Also in the pic, note that the alarm guys use set-screw type fittings. This is not an area that gets hosed down, so there probably is no requirement to use compression type fittings. Also, the alarm wires are arguably 'power limited' circuits, with less exacting requirements than power circuits.
The new RT fittings with the gaskets and seals are great for this application, along with a little bit of duct seal putty. You want to get rain in the light fixtures and switches? From the weather system that gets created inside the conduits that pass to the outside of this cooler, as the alarm guys might find out down the line. Sealing is required by 300.7(A)
I have seen light fixture jelly jars like that full from condensation. The colder it is inside, and the hotter is outside, add humitity, and you got a micro climate thunder storm.
Mark Heller "Well - I oughta....." -Jackie Gleason
Re: "Other Codes"...Health Regs#122602 12/05/0508:18 AM12/05/0508:18 AM