Class III systems, if located in the same building with other occupancies, shall be separated from the remainder of the building vertically and horizontally by construction having a fire-resistance rating of not less than one hour with openings protected by approved fire doors, except that such separation shall not be required for operations incidental to or in connection with the dry cleaning business, such as laundering, scouring, scrubbing, drying, pressing or ironing, and the requirement for such separation may be waived at the discretion of the Director based upon consideration of such factors as type of building construction, nature of occupancy, storage and operating capacity of the system and extent of private fire protection provided.