[AIVC, Air infiltration and ventilation glossary, 1992]:
air taken from the external surroundings and therefore not previously circulated through the system.

[ASHRAE Standard 62.1]:
ambient air and ambient air that enters a building through a ventilation system, through intentional openings for natural ventilation, or by infiltration.

[ASHRAE Standard 62.2]:
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.

[EN 16798-3:2017, 1]:
air entering the system or opening from outdoors before any air treatment (ODA; colour Green)

[EN 14511-1:2022, 3.40]:
air from the outdoor environment.

[EN 12792:2003, 280]:
controlled air entering the system or opening from outdoors before any air treatment (coded green)

[ISO 16814:2008, 3.31]:
air entering the system, or opening from outdoors before any air treatment.