Plain English:
505.1 general: Domestic cooking exhaust equipment has its own rules. If you show a hood, downdraft, or OTR microwave on plans, IMC 505 applies.
505.2 equipment listings
Fans for overhead hoods and non-integral downdrafts: must be listed and labeled to UL 507.
Hoods and downdrafts with integral fans: UL 507.
Ranges/cooktops with integral downdraft: listed to ANSI Z21.1 or UL 858.
Over-the-range microwaves with integral exhaust: listed to UL 923.
In short: every "domestic" exhaust device around the cooktop must be a listed assembly, not a field-built science project.
505.3 exhaust ducts
Discharge to outdoors through sheet metal ducts: galvanized steel, stainless, aluminum, or copper.
Ducts need smooth inner walls, be airtight, and have a backdraft damper.
I-1 and I-2 installs must also meet IBC and IFC 904.15 plus 505.7 or 505.8.
Exceptions:
Listed ductless hoods are allowed to recirculate when installed per manufacturer and Chapter 4 ventilation is otherwise met.
Downdraft systems can use Schedule 40 PVC under a slab on grade only if: the duct is fully buried in sand/gravel, and the PVC stub-ups are no more than 1 inch above the interior slab and exterior grade, with solvent-cemented joints.
On Plans: Why it matters
Common redlines: unlisted hoods or fans, "any flex" tied into random ducts, PVC used above grade, or ductless hoods shown with no Chapter 4 ventilation story. IMC 505.1-505.3 is where you prove the equipment is listed and the duct actually belongs there.
Code Path: Where to show it
M-001: "IMC 505 DOMESTIC COOKING EXHAUST" note calling out listed equipment (UL 507 / UL 923 / UL 858 / ANSI Z21.1) and duct materials to outdoors, with ductless-hood exception.
M-101: Hood and downdraft locations with duct routing and any under-slab PVC downdraft notes.
Check: Do
Ask for actual appliance models early and verify listings.
Keep domestic kitchen exhaust on its own duct path to the exterior with a backdraft damper.
Detail under-slab PVC downdrafts carefully if used.
Review Risk: Don't
Assume any fan and any flex-duct combo counts as a "domestic hood."
Show ductless hoods without confirming that Chapter 4 ventilation is still satisfied.
Field Tip:
Add a small "DOMESTIC COOKING EXHAUST-LISTING CHECK" note: hood type, listing standard, duct material, and "DUCTLESS? SEE CH-4 VENTILATION NOTE."
Masterbuild QA Lens
Domestic range exhaust systems must confirm: (1) the duct terminates to the exterior in residential applications; (2) the duct material is smooth interior (rigid metal preferred); (3) the equivalent length including elbows does not exceed the listed fan capacity curve. If a recirculating hood is used, confirm it is listed for that application and that the space ventilation is provided by another means per Chapter 4.
Drawing / Submittal Check
For residential cooking exhaust basics (505.1-505.3): the drawings must show the hood or range outlet, the duct routing to the exterior, the termination location with clearances from openings, and the type of protection at the termination. If the installation is a recirculating type, call out the filter type and AHJ acceptance on M-001. Confirm the duct is smooth metal - flexible duct is not permitted for cooking exhaust.
Common Review Risk
The most common 505 first-cycle
When To Escalate
Escalate when the residential cooking exhaust duct cannot be routed to the exterior without penetrating a fire-rated assembly in a way that conflicts with the required fire protection. In high-rise residential buildings, cooking exhaust duct routing through rated assemblies is a recurring coordination problem that requires the mechanical engineer, fire protection engineer, and AHJ to agree before construction.
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.
Duct System Coordination
Domestic cooking exhaust basics set minimum duct area, material (smooth metal), and whether a damper is required at the termination. Confirm duct size matches the listed range hood and that the termination detail is on the drawing.