7661 Air curtains (1) An air movement system for circulating air across the opening between two spaces of differing temperatures 7662 Unitary fans for spot ventilation (2) Unitary fans provided within building spaces to accelerate air movement at spot locations or to provide general air movement 7663 Unitary air heaters (0) Unitary air heaters, providing space heating by blowing air over heated elements 7664 Unitary supply fans (0) Unitary supply fans, supplying outside air to indoor spaces 7665 Unitary exhaust fans (1) Unitary exhaust fans, to exhaust or recirculate exhausted air 7666 Air treatment (2) Equipment to purify or improve air quality 7667 General air supply systems (4) Air supply systems (generally of untreated air) to provide general ventilation, spot ventilation, pressurized supply for smoke control, and make-up air 7668 Warm air heating systems (2) Systems using heat from a remote source to provide a ducted supply of warmed air