The boundary between classified locations is determined by the AHJ. I worked at a P&G plant that uses alcohol in their products. The tanks used for storing the finished product were located in an open area and the area within 10' of the tanks was Class I Div 2. The boundary is an imaginary line and not a wall, which P&G documents with drawings.
If you locate the control panel in a classified area, it must be rated for that location. Check with the AHJ to determine the boundary.
