airshed

[air-shed]
noun Meteorology.
  1. a geographical area within which the air frequently is confined or channeled, with all parts of the area thus being subject to similar conditions of air pollution.

Origin of airshed

First recorded in 1910–15; air1 + (water)shed
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for airshed

Historical Examples of airshed