air drainagen.

1816 Ann. Philos. 7 119 Wherever the workings of the mine..should render it impossible to form these channels of connexion with established air shafts, a new air shaft should be formed to command the upward air-drainage of the new workings.

1847 J. Conolly Constr. & Govt. Lunatic Asylums ii. 32 A general preference seems now given to providing for the general warmth of a building by the admission..of air warmed by passing over pipes containing hot water, provision being also made for the passing out of foul air... This plan of ‘air-drainage’ is adopted in the plan for the Derby asylum.

1851 Jrnl. Royal Agric. Soc. 12 378 Mr. S. Hutchinson..has introduced a system of ‘air-drainage’: the parallel tile-drains..empty into a covered outfall-drain... Another drain at the upper side of the field joins the other ends..and is made to communicate with the open air by means of ‘respirators’, or gratings.

1872 J. P. Henry Resources State Arkansas 26 The cause of this [fruitfulness] is attributed to the ridges and valleys of the country, thereby securing a perfect water and air drainage, and complete immunity from late frosts.

1944 Geogr. Jrnl. June 252 Valleys and basins are more frosty, depending again on the degree to which the relief and other factors permit air drainage from extensive uplands inland.

1994 J. M. Vargas Managem. Turfgrass Dis. (ed. 2) vii. 170 Diseases like..powdery mildew, and gray leaf spot are more severe where air drainage is poor.