Rule 693. An open building includes all operations conducted in the open air where equipment is in the open with platforms used for necessary access, sometimes with roofs or canopies to provide shelter, but without walls as distinguished from an enclosed building. An open building shall have exit facilities providing at least 1 means of escape from any point subject to employee occupancy, such means of escape affording safety from fire or smoke therefrom, explosion or release of fumes.
Mich. Admin. Code R. 408.10693