Overlapping Air Envelopes
When two bodies come close enough to each other, the air envelopes merge, and the Air Quality around the smaller body changes to match that of the larger body. When the bodies later move away from each other, each one reclaims and retains its own air envelope.
For example, if a damselfly ship with a foul air envelope enters the atmosphere a planet with fresh air, the two air envelopes merge, and the damselfly ship’s air quality changes from foul to fresh. If that ship then merges its fresh air envelope with the deadly air envelope surrounding a derelict ship, the damselfly ship’s air quality would change from fresh to deadly.
The air envelope around a body or ship can be fresh, foul, or deadly. Air can change from one quality to another over time.
Also see Personal Air Bubbles.