Issue link: https://hi.iaq.net/i/148954
atmospherically vented: combustion appliance venting that is not powered by a fan and relies on air inside the pressure boundary to replace the vented air. balanced system: two or more fans that simultaneously supply outdoor air and exhaust building air at substantially equal rates such that both the total supply and total exhaust flow rates meet the required fan flow rate. If the supply and exhaust points are both connected to a central forced air distribution system then the central system fan must operate simultaneously with the ventilation fan. bathroom: any room containing a bathtub, a shower, a spa, or a similar source of moisture or a toilet, urinal, or similar sanitary device. conditioned space: the part of a building that is capable of being thermally conditioned for the comfort of occupants. contaminant: a constituent of air that may reduce acceptability of that air. direct-‐vented: combustion appliance venting that is powered by a fan and does not rely on air inside the pressure boundary to replace the vented air. direct exhaust-‐vented: combustion appliance venting that is powered by a fan and relies on air inside the pressure boundary to replace the vented air. distributed ventilation system: a ventilation system that supplies outdoor air directly to the common area and each bedroom. forced air distribution system: an air duct and fan system whereby ducts supply air to all habitable spaces and a provision for return air exists from all habitable spaces served with supply air. exhaust system: one or more fans that remove air from the building, causing outdoor air to enter by leakage paths through the building enclosure. exhaust flow, net: flow through an exhaust system minus the compensating outdoor airflow through any supply system that is interlocked to the exhaust system. habitable space: building space intended for continual human occupancy; such space generally includes areas used for living, sleeping, dining, and cooking but does not generally include bathrooms, toilets, hallways, storage areas, closets, or utility rooms. high-‐polluting events: isolated and occupant-‐controllable events that release pollutants in excess quantities. Typical cooking, bathing, and laundry activities are not considered high-‐ polluting events.