Section 501.2/Exhaust Required
IMC 501.2 identifies spaces requiring mechanical exhaust ventilation including bathrooms, kitchens, parking garages, and other spaces where contaminants are generated.
Section 501.2 requires exhaust systems where the IMC or other codes mandate contaminant removal. Spaces requiring exhaust include: bathrooms and toilet rooms (Section 403.3), commercial kitchens and cooking equipment (Section 505), clothes dryer exhaust (Section 504), hazardous exhaust for flammable vapors and gases (Section 502), parking garages (Section 404), laboratory fume hoods, and any space where code-required exhaust rates are specified. The exhaust system must discharge outdoors per Section 501.3, with termination points located at least 3 feet from property lines, openable windows, and outdoor air intakes for most exhaust types, and at least 10 feet for hazardous and grease-laden exhaust. Exhaust air from one space must not be directed into another occupied space. The exhaust rate must meet the minimum specified in the applicable section or in ASHRAE 62.1 Table 6.2.6.2, whichever is more restrictive. Makeup air per Section 508 must be provided for all exhaust systems.
Why this section exists
Exhaust systems remove contaminants at their source before they spread throughout the building. Without exhaust, odors from bathrooms migrate into corridors, grease from kitchens deposits on building surfaces and HVAC equipment, moisture from laundry causes mold growth, and vehicle exhaust in parking garages creates carbon monoxide exposure risks. The discharge location requirements prevent exhausted contaminants from being re-entrained into the building through outdoor air intakes or open windows. Makeup air provisions prevent the building from operating under excessive negative pressure, which can cause backdrafting of combustion appliances, difficulty opening doors, and reduced exhaust system performance.
What plan reviewers look for
Plan reviewers check every bathroom, kitchen, parking garage, and laundry room for exhaust systems on the mechanical drawings. They verify exhaust CFM meets the code-required rate. They check the roof plan or wall elevations for exhaust termination locations and verify the separation distances from air intakes, windows, and property lines. They check for makeup air provisions per Section 508. For commercial kitchen hoods, they verify the Type I/II hood classification and grease-rated ductwork. They verify exhaust air is discharged outdoors and not recirculated through the supply air system.