[1] Himalayan Club Vice President Meher Mehta characterized Kellas' papers A Consideration of the Possibility of Ascending the Loftier Himalaya and A Consideration of the Possibility of Ascending Mt Everest as "key catalysts in driving scientific thinking into climbing big peaks.

His studies included the physiology of acclimatization in relationship to important variables like altitude, barometric pressures, alveolar PO2, arterial oxygen saturation, maximum oxygen consumption, and ascent rates at different altitudes.

"[2] In 1978, Kellas' suggestion was verified by Reinhold Messner and Peter Habeler when they made the first ascent of Mount Everest without supplemental oxygen.

He had made at least ten first ascents of peaks over 6,100 m (20,000 ft) including Pauhunri, 7,128 m (23,386 ft), in Sikkim, which was the highest peak climbed up to that point, although this was only discovered 80 years later.

[3] Kellas died of a heart attack in 1921 near the village of Kampa Dzong, Tibet, on his way from Sikkim to the first expedition to Everest.