Ventilation, Exhaust, and Indoor Air Quality
This domain tests ventilation and exhaust design: outdoor air, local exhaust, kitchen hoods and grease ducts, bathroom and dryer exhaust, makeup air, termination, balancing, and indoor air quality controls.
Core rules
- Ventilation must provide outdoor air for occupants and makeup air for exhaust systems. Exhaust cannot create unacceptable negative pressure that backdrafts fuel-burning appliances.
- Local exhaust is required for bathrooms, kitchens, and other contaminant sources. Exhaust must terminate outdoors, not into an attic, crawlspace, or living space.
- Kitchen grease ducts must be constructed, sealed, supported, and cleaned as required for grease service, with proper clearance and access. Recirculating hoods are limited to applications allowed by code.
- Dryer exhaust must be smooth, limited in length and fittings, and terminate outdoors with a backdraft damper. Flexible transition duct is restricted.
- Systems must be balanced so design airflow is achieved. Carbon monoxide alarms and other IAQ controls may be required where combustion appliances or attached garages create risk.
Worked example
A bathroom exhaust fan is ducted into the attic and stops above the insulation. The plan reviewer should reject it: moisture-laden air must terminate outdoors, with a backdraft damper and a duct route that does not trap condensation. Discharging into the attic creates mold and does not meet the exhaust intent.
Traps
Terminating exhaust in an attic or crawlspace; using a recirculating hood where grease exhaust is required; excessive dryer duct length or crushed flex; ignoring makeup air; and failing to balance or verify airflow.