: Outdoor-Air Intake Location (401.4)
Plain English: Plain English Highlights
401.4(1): Intakes not less than 10 feet from lot lines and from other buildings on the same lot.
401.4(2): Keep not less than 10 feet horizontally from contaminant sources (vents, streets, alleys, parking, loading). You may be closer to streets/alleys/parking/loading only when the intake is not less than 25 feet above those surfaces. If fronting a street/public way, measure from the nearest edge.
401.4(3): If a source is within 10 feet horizontally, place the intake not less than 3 feet below that source. Exception: no separation needed for an individual dwelling unit using a listed combo intake-exhaust fitting installed per the fan manufacturer.
401.4(4): In flood hazard areas, set intakes at or above the elevation required for utilities and attendant equipment by IBC 1612.
On Plans: Why It Matters
Redlines here are siting errors: measured from the wrong street edge, missed the 25-foot vertical relief, intake set level with nearby exhausts, or intake below flood elevation. Resolve on the site plan before louvers are released.
🧾 Where To Show It (sheet map)
M-001: "OUTDOOR-AIR INTAKES PER IMC 401.4. SHOW OFFSETS TO LOT LINES, BUILDINGS, STREETS, ALLEYS, PARKING, LOADING, AND EXHAUSTS. WHEN FRONTING A STREET/PUBLIC WAY, MEASURE FROM THE NEAREST EDGE. IN FLOOD HAZARD AREAS, SET ABOVE IBC 1612."
M-101+: Dimension strings from each intake to lot line, on-site buildings, street/public way, parking/loading, and to nearest exhaust/plumbing vent; show vertical offsets where using the 25-foot allowance; draw flood design elevation.
M-501/502: OA louver detail (drainable section, screen, flashing continuity) with MI page; note vertical-offset logic and street-front measurement; cut a flood line through the wall section.
M-601 (Schedule adds): Intake ID | Serving System | Dist. to Lot Line | Dist. to Building | Dist. to Street/Public Way | Dist. to Parking/Loading | Nearest Exhaust/Plumbing Vent (H/V) | Intake Elev. & Flood Check | Louver Model + AMCA ref | MI Page.
Field Tip: Quick Field Tip
If you cannot keep 10 feet horizontally from streets/parking, raise the intake to not less than 25 feet above that surface and show the dimension.
When facing a street/public way, pull distance from the closest edge, not the centerline.
Keep the intake at least 3 feet below any exhaust located within 10 feet; avoid level terminations.
In mapped flood zones, set the intake above the required elevation or detail an approved protection method.
Comment "IMC401" for the Intake and Protection Kit. DM "ADVISORY" for a preliminary plan review before you file.
Masterbuild QA Lens
Ventilation posts should translate code language into a permit-ready airflow story: occupancy, outdoor air quantity, intake location, exhaust relationship, controls, and any exception being used.
Drawing / Submittal Check
Verify the drawings show occupancy basis, ventilation method, outdoor air path, intake and exhaust separation, transfer air assumptions, controls, and schedule values that match the calculation.
Common Review Risk
The common review risk is an airflow value without a traceable basis. Another risk is showing outdoor air on a schedule while the plan, intake location, or control sequence tells a different story.
When To Escalate
Escalate for healthcare spaces, high-occupant-load areas, unusual contaminants, existing air handlers with unknown outside air capacity, or any project where pressure relationships matter.
Load Assumption Check
For load-driven decisions, make the assumptions visible: weather basis, orientation, envelope, occupancy, ventilation, equipment gains, and any existing-building limitations that affect capacity.
Special Exhaust Coordination
For specialty exhaust, start with the contaminant and source. Then confirm capture method, duct material, routing, discharge, separation, controls, and whether another consultant or AHJ review is required.