Commencing May 1, 1998, or in the case of existing restaurants, at the time of a transfer of ownership, the replacement or acquisition of equipment, or the commencement of any remodeling project requiring the permit holder or its landlord to obtain a building permit, commercial equipment will be recommended for use in food service establishments. It is recommended that all equipment be designed for commercial use, and approved by the National Sanitation Foundation (NSF), or its equivalent.