NFPA 68 Deflagration in (4) four rectangular Rooms that share some common walls.

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Imagine (4) four rectangular rooms, about 10 feet wide x 20 feet long x 10 feet high. Therefore, you have (3) three interior walls that are shared. For simplicity let's say I have designed the walls to be 8", grout-filled, reinforced CMU walls. Would the "shared" wall be (2) two 8" cmu walls sitting right beside each other, one wall for each of these rooms, or would the "shared" wall be a single 8" wall that would be shared by both rooms?