: Intake Protection and Contaminant Sources (401.5-401.6)
Plain English: Plain English Highlights
401.5: Outdoor air intakes that terminate outside must have corrosion-resistant screens, louvers, or grilles sized per Table 401.5 and suited to local weather. Intakes in exterior walls must also meet IBC exterior-wall opening protectives. In hurricane-prone regions, louvers must comply with AMCA 550.
401.5 Table (opening sizes): Residential not less than one quarter inch and not more than one half inch. Other occupancies greater than one quarter inch and not more than one inch. Use the short side for rectangles, the diameter for rounds, any side for squares.
401.6: Stationary local sources that produce particulates, heat, odors, fumes, spray, vapors, smoke, or gases in irritating or injurious quantities must have an exhaust system per Chapter 5, or equivalent collection and removal. Exhaust must discharge directly to an approved exterior location.
On Plans: Why It Matters
Fast redlines: wrong mesh opening, no AMCA 550 where required, missing IBC opening-protective note, and routing process exhaust to return/relief instead of a dedicated Chapter 5 discharge.
🧾 Where To Show It (sheet map)
M-001 (General Notes): "Outdoor air intake protection per IMC 401.5. Opening sizes per Table 401.5. Hurricane-prone structures: louvers comply with AMCA 550. Exterior wall intake openings meet IBC exterior wall opening protectives. Stationary contaminant sources per IMC 401.6 with Chapter 5 exhaust and direct discharge to exterior."
M-101+ (Plans): Tag each intake (Louver ID) and each Chapter 5 source (Source ID); show intake protection and discharge routes/terminations.
M-501/502 (Details): Louver section with drainage path, flashing continuity, bird or rodent screen, clean-out access; Chapter 5 capture hood or enclosure details with duct pickup and discharge.
M-601 (Schedules - adds): Louver Model; Opening Size Range per 401.5; Screen Material and Mesh; Free Area and Face Velocity Basis; AMCA 500-L reference; AMCA 550 (Yes or No, if applicable); IBC Opening Protective Note; MI page. For Chapter 5 sources: Source ID; Capture Type; Design cfm; Discharge Location; Balancing and interlocks.
Field Tip: Quick Field Tip
Verify actual mesh/slot dimension against Table 401.5 (not nominal brochure size).
In hurricane regions, submittals must show AMCA 550 for the exact model and size.
Keep screens removable; louvers drain away from the wall.
Process exhaust: dedicated duct to exterior with compliant discharge separation - never into general return/relief.
Comment "IMC401" for the Intake and Protection Kit.
DM "ADVISORY" for a fast siting sweep 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.
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.