In 1978, Kellas' suggestion was verified by Reinhold Messner and Peter Habeler when they made the first ascent of Mount Everest without supplemental oxygen. However, Kellas was also one of the earliest scientists to suggest use of supplemental oxygen on high mountains such as Mount Everest; the first ascent of Everest and most subsequent ascents (as well as some ascents of lower peaks) have done so. A distant relative (Simon Kellas) is now employed by The Physiological Society (UK).