Plain English:
501.3 exhaust discharge: Route exhaust outdoors where it won't bother people and can't be pulled back into any system. Never into attics or crawl spaces. Keep it off walkways.
Exceptions:
Whole-house attic fans may discharge to private attics in dwellings.
Listed commercial cooking recirculating systems are allowed.
Listed domestic ductless range hoods are allowed only when installed per instructions and Chapter 4 ventilation is otherwise provided.
501.3.1 outlet location (minimum clearances):
1. Explosive or flammable product-conveying: 30 ft to property lines; 10 ft to operable openings; 6 ft from exterior walls/roofs; 30 ft to combustible walls and to operable openings in the discharge direction; 10 ft above grade.
2. Other product-conveying: 10 ft to property lines; 3 ft from exterior walls/roofs; 10 ft to operable openings; 10 ft above grade.
3. Environmental air: 3 ft to property lines; 3 ft to operable openings (not for Group U); 10 ft to mechanical air intakes. Listed intake/exhaust combo fittings are allowed within a single dwelling or sleeping unit when installed per instructions.
Flood areas: Set outlets at or above the IBC 1612 elevation.
See also: 504.4 dryers; 506.3.13/506.4/506.5 kitchens; 511.2 dust; 512.4 subslab soil; 513.10.3 smoke; 1105.7 refrigerant; 1105.6.1 machinery rooms.
On Plans: Why it matters
Common stops: missed separations, terminations too low above grade, re-entrainment into intakes, attic/crawl terminations, and "ductless range hood" notes without separate Chapter 4 ventilation.
Code Path: Where to show it
M-001: Discharge rules, exceptions, flood-elevation note.
M-101 and exterior elevations: Dimensions to lot lines, openings, intakes, and grade; show discharge direction.
M-501: Wall/roof termination details with throw direction, backdraft damper, weather protection.
M-601 schedules: Termination ID, discharge type, required vs provided separation, height above grade.
Check: Do
Dimension each outlet to openings, intakes, property lines, and grade.
Aim discharge to avoid people paths and any intake re-entrainment.
Coordinate flood elevations early.
Review Risk: Don't
Treat a ductless range hood as outdoor exhaust. If used, show Chapter 4 ventilation elsewhere and cite listing/instructions.
Terminate near intakes or openings.
Miss the 10 ft above grade rule where it applies.
Field Tip:
Add a small "termination separation schedule" on M-001 listing each outlet and its nearest intake/opening/grade with required and provided distances.
Masterbuild QA Lens
Exhaust discharge location failures are caught at the site plan review, not the mechanical review. Before submittal, check every outdoor exhaust termination against the Table 501.3.1 separations for its classification. Dimension separations from lot lines, operable openings, and air intakes on both the floor plan and the exterior elevations. A schedule note without dimensions is not sufficient.
Drawing / Submittal Check
Exhaust outlet and discharge location must be shown on the mechanical drawings and coordinated with the site plan. Verify outlet height above grade, distance from property lines, distance from openings (windows, doors, air intakes), and prevailing wind direction where applicable. Each is a code-required minimum that must appear on the drawings, not in the spec alone.
Common Review Risk
Discharge location errors are most common on urban infill projects where the only available outlet is near a property line, window, or building intake. The most expensive version: an exhaust outlet that was coordinated with the architecture but not with the mechanical intake on the same building. Check both the site plan and the roof plan for conflicts before submitting.
When To Escalate
Escalate when the discharge location conflicts with neighboring property requirements, environmental permits, or historic district restrictions on visible mechanical equipment. Urban projects in dense settings frequently have exhaust termination constraints that require coordination with the local planning authority in addition to the building department.
Load Assumption Check
Exhaust discharge location and outdoor air intake separation affect the effective OA quality and the infiltration load from door openings. Confirm that exhaust and intake locations are dimensioned on the site plan and that no recirculation credit is taken where recirculation is possible.
Kitchen Exhaust Coordination
For kitchen exhaust, tie the hood schedule, appliance lineup, grease duct route, cleanouts, fan discharge, fire suppression interface, and make-up air strategy into one reviewable story.