Intake Protection and Contaminant Sources (401.5-401.6)
Plain English:
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.
Code Path: DCV Controls Documentation
M-001 must state the DCV CO2 setpoint (ppm) and the minimum outdoor air rate at minimum occupancy for each zone with demand-controlled ventilation.
Controls sequence diagram must show the OA damper response at: below setpoint, above setpoint, and during unoccupied periods.
DCV sensor locations must be shown on the mechanical and controls plans with setpoints noted.
Check: DCV and Shutdown Sequence
Confirm DCV sensor locations are shown on the plan and the controls sequence addresses the OA damper at three conditions: below setpoint, above setpoint, and unoccupied.
For shutdown per 401.7, confirm the controls sequence shows OA damper behavior during fire alarm events.
Verify the minimum outdoor air rate at minimum occupancy meets the code minimum - DCV cannot reduce OA below the absolute minimum.
Review Risk:
DCV systems that are specified but not commissioned are a common performance failure - sensors are installed but controls are not verified to respond to CO2.
CO2 setpoints not documented in the controls sequence are a consistent plan review comment - the setpoint must be specified, not left to the controls contractor.
OA dampers that close fully during unoccupied mode without a minimum ventilation provision violate 401.7 - the sequence must address minimum unoccupied ventilation requirements.
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.
Masterbuild QA Lens
Intake protection failures - wrong opening size, no AMCA 550 compliance in hurricane regions, missing IBC exterior-wall protective - are common first-cycle comments. Confirm the louver and screen schedule shows free area, opening size (min 1/4 in, max 1/2 in), and AMCA 550 compliance where required. Put it in the schedule, not just the spec.
Drawing / Submittal Check
For 401.5-401.7 (ventilation controls, demand-controlled ventilation, and shutdown): the drawings must show the DCV sensor locations, the CO2 setpoints, and the minimum outdoor air rate at minimum occupancy. The controls sequence must show what happens to outdoor air dampers during unoccupied periods, fire alarm events, and smoke control activation. A ventilation controls sequence that does not address fire alarm and smoke control modes will get a comment.
Common Review Risk
Demand-controlled ventilation systems that are specified but not commissioned are a common building performance failure. The CO2 sensors may be installed, but if the controls are not verified to open the outdoor air damper when CO2 rises, the system does not perform as designed. Confirm the commissioning protocol includes a DCV functional test: occupants simulate high-CO2 conditions and the outdoor air damper is confirmed to open to the required minimum.
When To Escalate
Escalate when the demand-controlled ventilation commissioning test fails - when the CO2 sensor activates but the outdoor air damper does not open to the required minimum. A failed DCV functional test requires coordination between the controls contractor, the mechanical contractor, and the test and balance contractor to identify and correct the interlock failure.
Load Assumption Check
Ventilation recirculation and air-cleaning alternatives affect the effective OA fraction and the resulting latent load on the cooling coil. Confirm that any recirculation or filtration credit is calculated per the code method and documented on the drawings.
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.