[It] is evident, not only from considering the Effects of the Engine, which exchanges great Quantities of bad, for good Air; but also from the Event … - Stephen Hales

He proposes by this means to cure intermitting Fevers, by having the Air in the Room rarefied in the cold Fit, and condensed in the hot Fit; during the whole time of which, the Patient is to continue therein: And recommends the use of it, among other Distempers, to cure the Stone and the Pox.

A Translation of which ingenious Treatise, was communicated to me by Dr. Mortimer; in which he says, "In Hospitals and Barracks for the Sick, this Machine is placed in the , from whence two or three Pipes go down, some Inches thro' the Ceiling, into each Room where the Sick lie; and thus draw out all the unwholesome Air and Stench, which does more harm than any Physick can repair. And at the same time, has this accidental Benefit, That those who begin to mend, may give themselves a proper Exercise, in working the Machine: Only they ought to take care to keep all the Garret-Windows open, while the Machine is a going. In Men of War and Hospital-Ships, this Machine is placed on the upper Deck, directly over the great other Hatch: And then the Pipe, which goes down between the Decks, draws out the unwholesome Air; which is instantly supplied by fresh.

For this Engine <nowiki>[</nowiki>] had a Privilege for Life granted him by the King and Senate of Sweden, dated the 20th October 1741...