airshed

[air-shed]

noun Meteorology.

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

On 7th June two of our airmen destroyed an airshed and a Zeppelin north of Brussels.
The Childrens' Story of the War, Volume 4 (of 10)
James Edward Parrott