I could use a second opinion. I am currently dealing with two sheds that are used for HAZMAT storage. NFPA defines this as a, "Inside Storage Area" since there are used for storage of small containers of flammable liquids. According to NFPA 30, the wiring must meet the requirements in Chapter 8. If you go to chapter 8, there is a nice table except that there is no catagory for an inside storage area. The nearest one I get close to is towards the bottom is, "Inside rooms or storage lockers used for Class I liquides" Am I correct to use this one? My concern is with the wiring on the outside of the building. The insde is done iaw NEC but on the outside is a mixture of x-proof and regular wiring. the deviding line between the two is an illusive bugger. I use to do some x-proof wiring years ago at a fuel storage facility but I was just an apprentice and was told to just do this this way and the codes have changed a bit since then.