Plain English:
404.1 (Control): Garage ventilation must run continuously or automatically via CO + NO₂ detectors listed to UL 2075 and installed per manufacturer instructions.
404.1 (Airflow): Automatic systems cycle between Full-On >= 0.75 cfm/ft^2 and Standby >= 0.05 cfm/ft^2 of the floor area served.
404.2 (Accessory rooms): Offices/booths/waiting rooms that connect to a public garage must be positive pressure to the garage and ventilated per -403.3.1 (use Table 403.3.1.1 for rates).
Calculation Check: Step-by-Step (mirror on M-601)
1. Pick strategy (404.1): Continuous or automatic with CO + NO₂ detection.
2. Size fans (404.1):
Full-On cfm = 0.75 x ft^2
Standby cfm = 0.05 x ft^2
3. Controls (404.1): Two-speed/VFD; CO/NO₂ thresholds for Standby ↔ Full-On; fail-safe to Full-On on detector/BAS fault.
4. Accessory rooms (404.2): Provide OA per 403.3.1 and keep supply > exhaust to maintain positive pressure; detail door relief/seals.
5. Detectors (404.1): Note UL 2075 on M-001; mount/space per IOM; include calibration/testing notes.
Code Path: Where to Show It (sheet map)
M-001: "IMC 404 garage ventilation; CO+NO₂ detectors UL 2075; modes: 0.75/0.05 cfm/ft^2. Accessory rooms positive to garage; OA per 403.3.1."
M-101+: Ventilation fans/duct layout, detector locations/heights, pressure arrows at doors.
M-601: Garage fan schedule (Full/Standby cfm, VFD/2-speed), detector model/listing, accessory-room OA and pressure offset.
M-603/M-002: Mode logic, thresholds, fault -> Full-On, trending/alarms.
E (coord): Power/BAS points; emergency power if required by local amendments.
Coordination Check: Frequent Redlines
NO₂ detectors missing (CO only shown).
UL 2075 not cited or mounting ignores IOM.
Standby 0.05 cfm/ft^2 not proven (no low-speed path).
"Positive pressure" noted but no supply-exhaust math or door sealing.
Check: Garage System Sizing and Controls
M-001 must state the ventilation method: continuous (0.75 cfm/sf) or CO/NO2-automatic (with standby at 0.05 cfm/sf and Full-On at 0.75 cfm/sf).
M-601 must show fan cfm at Full-On and Standby modes with CO/NO2 sensor locations, quantities, and control setpoints on the controls diagram.
Control diagram must show the logic transitioning between Standby and Full-On and confirm accessory office space pressure intent (positive relative to garage).
Review Risk:
Designing to the wrong ventilation method - continuous system sized and submitted as CO/NO2-automatic, or vice versa - is the most common 404 rejection.
CO/NO2 sensor locations not shown on the control diagram or plans are a consistent plan review comment - show sensor positions, quantities, and setpoints.
Accessory office spaces without a confirmed positive pressure intent relative to the garage are a common coordination gap.
Field Tip:
Place CO in expected accumulation zones; NO₂ near diesel paths; follow each detector's IOM (heights differ).
Trend ppm, fan speed, cfm; show a BAS graphic that proves mode switching and fault fail-safe.
Masterbuild QA Lens
Garage ventilation compliance depends on the control sequence, not just the fan cfm. Confirm that the controls sequence for CO/NO2-triggered automatic operation - including the set points, Standby cfm (0.05 cfm per sq ft) and Full-On cfm (0.75 cfm per sq ft) - is on the mechanical control diagrams. Accessory offices must be positive pressure relative to the garage. Show the pressure intent on M-101.
Drawing / Submittal Check
For 404 garage ventilation: M-001 must state the ventilation method (continuous or CO/NO2-automatic); M-601 must show the fan model, cfm at Full-On (0.75 cfm/sf) and Standby (0.05 cfm/sf); the control diagram must show CO/NO2 sensor locations, setpoints, and the control logic that transitions between Standby and Full-On. Accessory office pressure intent (positive vs garage) must be shown on M-101.
Common Review Risk
The most common 404 rejection: a garage exhaust system designed to the 0.75 cfm/sf continuous rate for a CO/NO2-automatic control system - or vice versa. The two systems have different fan sizing, different controls, and different minimum cfm requirements. Confirm which system type is being designed before sizing fans or writing the controls sequence.
When To Escalate
Escalate for parking garage ventilation systems that must comply with both the IMC and a local air quality regulation, when the CO monitoring system triggers at levels that do not match the code thresholds, or when the parking garage is enclosed within a mixed-use building where the exhaust cannot be discharged without affecting adjacent occupied spaces. All three are common sources of permit disputes on urban parking garage projects.
Duct System Coordination
Enclosed parking garage exhaust ducts must resist vehicle exhaust exposure and meet discharge height and direction requirements. Coordinate duct material, routing, and outlet placement on the drawings.
Ventilation Coordination
For parking garage ventilation (IMC 404): the exhaust outlet and the outdoor air intake must be separated from adjacent building intakes, operable windows, and occupied exterior spaces (courtyards, loading areas, pedestrian entries). Parking garage exhaust in urban buildings is a common source of ventilation coordination conflicts with neighboring buildings.