If your exhaust is over 600 degrees F, it's not "just another exhaust outlet." IMC 510.2 forces you into chimney rules with specific thickness, lining, clearances, and termination heights.
Plain English:
510.2 trigger
Exhaust outlets exceeding 600 degrees F (315 degrees C) must be designed as a chimney per Table 510.2 (single-wall metal chimneys).
Minimum wall thickness (all categories) - 0.127 in (No. 10 MSG)
Termination + lining basics (Table 510.2)
High-heat appliances (over 2,000 degrees F)
1. Lining: 4 1/2 in laid on 4 1/2 in bed
2. Termination: 20 ft above roof opening
3. Termination relative to building: 20 ft above any part of building within 50 ft
4. Clearance: per design engineer (must prevent combustibles exceeding 160 degrees F)
Medium-heat appliances (2,000 degrees F max)
1. Lining: up to 18 in dia: 2 1/2 in; over 18 in: 4 1/2 in on 4 1/2 in bed
2. Termination: 10 ft above roof opening
3. Termination relative to building: 10 ft above any part of building within 25 ft
4. Clearance to combustibles: 36 in interior, 24 in exterior
Low-heat appliances (1,000 degrees F normal operation)
1. Lining: none
2. Termination: 3 ft above roof opening
3. Termination relative to building: 2 ft above any part of building within 10 ft
4. Clearance to combustibles: 18 in interior, 6 in exterior
5. Clearance to noncombustibles: up to 18 in dia: 2 in, over 18 in: 4 in
Lining notes
Lining extends bottom to top of outlet (general).
For the noted condition: lining extends 24 in below connector to 24 ft above.
On Plans: Why it matters
Common misses: showing a hot exhaust as "typical duct," missing the termination height criteria, and ignoring the clearance-to-combustibles impacts (which drives routing, roof layout, and supports).
Code Path: Where to show it
M-001: "EXHAUST >600 degrees F SHALL BE DESIGNED AS CHIMNEY PER IMC 510.2 / TABLE 510.2" + identify category (low/medium/high heat).
Roof plan: termination heights + dimension to "parts of building within X ft" as applicable.
Sections/details: clearances to combustibles/noncombustibles and lining requirement.
Check: Do
Call out the temperature basis and which Table 510.2 row applies.
Dimension termination heights on the roof plan (don't make plan reviewer guess).
Review Risk: Don't
Don't route >600 degrees F exhaust like standard ductwork through tight combustible spaces.
Don't omit the "within 10/25/50 ft" termination check.
Field Tip:
Use the quick "600 degrees F -> CHIMNEY" check:
1. Confirm exhaust temperature >600 degrees F.
2. Select low / medium / high heat row.
3. On the roof plan, note A) ft above roof opening and B) ft above any part of building within X ft.
4. Verify clearances won't force a reroute late.
Masterbuild QA Lens
Section 510 listed exhaust systems must be installed per the manufacturer installation instructions and the listing requirements - not per general HVAC duct installation practice. Confirm the MI documents are cited on M-001, the AHJ has accepted the listed system as an alternative, and the design drawings reference the specific listed system model.
Drawing / Submittal Check
For 510.2 (exhaust outlets over 600 degrees F requiring chimney construction): the drawings must show the exhaust temperature at the outlet and confirm the chimney construction type is appropriate for the temperature. Cross-reference the chimney drawings. If the exhaust cools below 600 degrees F before discharge, show the temperature profile on the drawings.
Common Review Risk
High-temperature exhaust systems (over 600 degrees F) that were not identified as requiring chimney construction are a significant code compliance gap. Some high-temperature conveying systems (kilns, ovens, dryers) exhaust above 600 degrees F but were designed with standard duct because the temperature was not confirmed during design. Confirm the exhaust temperature range from the process equipment manufacturer before selecting the duct system type.
When To Escalate
Escalate when the high-temperature exhaust system requires a chimney that must penetrate a fire-rated roof assembly in an existing building. Chimney penetrations in existing buildings with inaccessible roof structure are a common source of hidden scope. Confirm the penetration condition before the permit is filed.
Duct System Coordination
Section 510.2 exhaust outlet requirements set minimum velocity and prohibit discharge into enclosed courts or shafts. Verify the duct outlet is sized to meet velocity requirements at design CFM and that the termination location is unobstructed.