California Code, Labor Code - LAB § 6703

Sections 6701 and6702 shall apply to all portable and all mobile internal combustion engines used inside factories, manufacturing plants, warehouses, buildings and other enclosed structures unless the operation of such an engine used inside a particular factory, plant, warehouse, building or enclosed structure does not result in harmful exposure to concentrations of dangerous gases or fumes in excess of maximum acceptable concentrations as determined by the standards board.