The observation that infants placed in an incubator after surgery sneezed and coughed, and that a pungent odor was generated within the incubator, led to a search for possible irritants. It was found that diethyl ether, exhaled by the infant during recovery from anesthesia, could be decomposed by contact with the electrical heating element in the incubator. In experiments with rabbits recovering from ether anesthesia and placed in the incubator, formaldehyde was found to be produced in concentrations as high as 370 ppm, far exceeding the threshold limits set for industrial atmospheres. The production of such irritants can be avoided with use of a heater so designed that the gases in the incubator do not come into contact with heating elements at high temperatures.
Mendenhall MK, Jenicek JA, Bryant JM. THERMAL DECOMPOSITION OF ETHER IN THE INFANT INCUBATOR. JAMA. 1960;173(6):651-653. doi:10.1001/jama.1960.03020240039007