Confirm the project uses the 2025 OMSC, mandatory since April 1, 2026, then trace ventilation, exhaust, equipment, duct penetrations of rated assemblies, and fuel gas piping and venting through the mechanical, architectural, and plumbing drawings. AI can flag conflicts; the mechanical designer and building official decide compliance.
What does the OMSC cover?
The Building Codes Division describes the Oregon Mechanical Specialty Code as governing mechanical systems permanently installed to control environmental conditions and related processes within buildings. Because it is based on both the IMC and the IFGC, fuel gas piping and appliance venting are reviewed under it too.
The Oregon Building Codes Division states that the 2025 OMSC is based on the 2024 International Mechanical Code and International Fuel Gas Code, took effect October 1, 2025 with a six-month phase-in during which the 2022 OMSC could be used, and became mandatory April 1, 2026. Checked October 15, 2026. Interim amendments and errata are posted on the same pages; confirm which edition the permit was applied for under.
Model code checks are in the IMC and IFGC guides. Commercial energy is in the OEESC guide, and one- and two-family dwellings use the ORSC.
Gather the mechanical and fuel gas documents
Collect the mechanical plans, schedules, and details, the ventilation calculations or schedule, the fuel gas piping plan and riser, appliance venting details, the architectural plans and wall types where ducts cross rated walls, the roof plan with equipment and exhaust terminations, and the plumbing drawings for condensate and gas.
Check which code each mechanical sheet cites; a sheet copied from another state may cite the model code alone.
Trace OMSC items through the set
| Review question | Sources to compare | Decision to record |
|---|---|---|
| Edition | Mechanical general notes, code analysis | Confirm the 2025 OMSC is cited rather than a model code or earlier edition. |
| Ventilation and exhaust | Ventilation schedule, plans, roof plan | Match outdoor air and exhaust to the spaces and terminations drawn. |
| Equipment and access | Equipment schedule, plans, sections | Check scheduled equipment appears on plans with access shown. |
| Rated penetrations | Duct plans, wall types, damper schedule | Find ducts crossing rated walls or floors without a damper or listed system. |
| Fuel gas piping | Gas plan, riser, appliance schedule | Match appliance loads and locations to the gas piping drawn. |
| Venting and terminations | Venting details, roof plan, elevations | Check vent terminations clear openings and air intakes as drawn. |
The mechanical drawing checklist gives a working log, and air distribution specifications are compared in the HVAC air distribution guide.
Example: a gas water heater with no gas line
Hypothetical example. The plumbing schedule lists a gas-fired water heater in a mechanical room. The OMSC fuel gas plan does not extend piping to that room, and the mechanical venting details show only the rooftop units.
The plumbing schedule lists a gas-fired water heater in Mechanical 104, but the fuel gas plan and venting details do not serve it. Confirm the fuel type and coordinate the gas piping, venting, and schedules.
The mechanical and plumbing designers confirm the appliance and update the drawings. The finding is a coordination question.
Review Oregon mechanical drawings with Groundbook
Upload the current drawings and specifications to Groundbook, and state the edition, amendments, and review scope in your instructions. Add the Oregon Mechanical Specialty Code edition the project uses from a copy you are licensed to use, where the license permits uploading it, and the jurisdiction’s published amendments. See how Groundbook works with local and licensed codes.
Compare the mechanical plans, schedules, ventilation information, fuel gas plans, venting details, roof plan, plumbing schedules, and architectural wall types. Flag model code citations instead of the OMSC, equipment missing from plans, ducts crossing rated assemblies without protection, and gas appliances not served by piping or venting. Use the supplied OMSC and cite both sources.
Groundbook links each potential finding to the sheets involved.
Document review does not size equipment, gas piping, or ventilation. Those remain with the mechanical designer and the building official.