For OSHPD projects, outdoor air intakes shall be at least 25 feet from exhaust outlets (CMC 407.2).
For product-conveying ducts, the distance required to openings into the building is 10 feet (CMC 506.9.2). However, a bathroom exhaust fan is not considered to be a product conveying duct.
The bathroom exhaust fan is considered to be an environmental air duct. The 3 feet distance is required to openings into the building for environmental air ducts(CMC 504.5).
However, rooftop terminations of exhaust systems are required to be separated by a minimum 10 foot distance to adjacent buildings, property lines, and air intakes. When the 10 foot horizontal separation from the air intake cannot be provided, a vertical separation of at least 3 feet is required (CMC 510.8.2).