1. Background, environmental, or surrounding air. When studying the dynamic and thermodynamic processes acting on an individual element such as an air parcel, cloud, smoke plume, raindrop, or ice crystal, ambient air represents the atmosphere outside of that element. The ambient air is often assumed to be static and of relatively large domain, within which the element resides. 2. The air that surrounds us, within which we live. When air pollutants of high concentration from exhaust or stack gases are emitted into cleaner air, the resulting polluted mixture is called the ambient air. National Ambient Air Quality Standards (NAAQS) apply to this final mixture, not to the undiluted emission gases.