24 C.F.R. § 3280.102
Air, exhaust means air discharged from any space to the outside by an exhaust system.
Air, outdoor means air from outside the building taken into a ventilation system or air from outside the building that enters a space through infiltration or natural ventilation openings.
Exhaust system means one or more exhaust fans that remove air from the building, causing outdoor air to enter by ventilation inlets or normal leakage paths through the building envelope.
Gross floor area means all space, wall to wall, including recessed entries not to exceed five (5) square feet and areas under built-in vanities and similar furniture. When the ceiling height is less than that specified in § 3280.104 , the floor area under such ceilings must not be included in the gross floor area. Floor area of closets must also not be included in the gross floor area.
Habitable room means a room or enclosed floor space arranged for living, eating, food preparation, or sleeping purposes not including bathrooms, foyers, hallways, and other accessory floor space.
Laundry area means an area containing or designed to contain a laundry tray, clothes washer and/or clothes dryer.
Mechanical ventilation means the active process of supplying air to or removing air from an indoor space by powered equipment such as motor-driven fans and blowers but not by devices such as wind-turbine ventilators and mechanically operated windows.
Natural ventilation means ventilation occurring as a result of natural forces, such as wind pressure or differences in air density, through intentional openings such as open windows or doors.
Supply system means one or more fans that supply outdoor air to the building, causing indoor air to leave by normal air leakage through the building envelope.
Ventilation means the process of supplying outdoor air to or removing indoor air from the manufactured home by natural or mechanical means. Such air may or may not have been conditioned.
24 C.F.R. §3280.102