What do I do when supply/return/exhaust mixed up?
Airflow/TAB Impacts From InstallationV136 field-polished — distinct TAB/airflow answer
Confirm the system tag before tying in. Supply, return, exhaust, and outside air ducts are not interchangeable.
Field checklist
- Find the tag on the drawing: SA, RA, EA, OA, MUA, or other system label.
- Trace the duct back to equipment, shaft, fan, VAV, or grille.
- Check airflow arrows and room served.
- Compare duct label/tag to the field piece or shop drawing.
- Ask before tying different systems together.
Ask foreman
This run/tag is unclear at [location]. Is this supply, return, exhaust, outside air, or make-up air before I connect it?
Do not
Do not connect duct because it is nearby or the same size.
Why it matters
Mixed systems can cause comfort, pressure, contamination, odor, and inspection problems.
Search words: supply return exhaust outside air mixed up sa ra ea oa mua airflow tag