Hours before Jamshedpur climber Hemant Gupta, 26, reached the peak of his ambitions - the 29,029-feet Everest - on the morning of May 26, he was gasping for breath at death zone.

Death zone is what climbers call a point at high altitude when there is not enough oxygen to breathe - sometimes only 30 per cent of what human beings inhale at sea level - which can cause a person to collapse.

Hemant met his death zone at 26,000-plus feet on the night of May 25.

"I left camp 4 (26,085 feet) at 9pm on May 26. When I felt low on oxygen, I realised this was a death zone and thought, okay, this is it. But I made it to the summit at 6.25am on May 27," Hemant, who has an IIT-Bombay BTech degree in metallurgical engineering and material science but decided on a career in adventure at Tata Steel Adventure Foundation, said from New Delhi over phone on Thursday.

The 10-day trek to 29,029 Everest peak had all elements of a cliff-hanger - risk, thirst, breathlessness, the constant battle of mind and body - but the young man said it was worth it.

The view from the top of the world "was breathtaking", he said. "I stayed at the peak for only 15 minutes. But it felt like a lifetime. I felt like staying on. Didn't want to take the descent route," he recalled, laughing.

Hemant was part of the 13-member expedition team that included two Greek nationals.

"I and the two Greek nationals managed to summit the Everest while the rest returned from camp 4. I think I had acclimatised well and had the stamina and endurance to annex the peak. I was also determined to not let this opportunity go waste as I missed annexing Everest in 2015 due to the earthquake in Nepal," Hemant added.

Dream peak annexed, reality bit hard.

Hemant left the summit at 6.40am on May 27 and reached camp 2 (21,000 ft) at 10pm that same night. "The journey from camp 4 to 2 was very tough as we ran out of water. There was not a single drop of water to drink. I felt weak and thirsty. We somehow managed to reach camp 2, where we stayed overnight and made it to the 17,600 feet base camp at 2pm on May 28," he said, adding they lived on rice, pulses, noodles and chocolates.

Hemant and Jamshedpur climber Payo Murmu, who could not summit Everest this time, reached New Delhi from Kathmandu on Wednesday.

Payo had been with Hemant in the 2015 Everest expedition. Both were holed up at camp 2 (21,000 ft) when the earthquake shook Everest and had to be rescued by a chopper.

"In fact, my family at Kota, Rajasthan, was so scared by that incident that they were against this year's expedition too," said Hemant. "Now, I am going to them and will stay at home for a week before returning to Jamshedpur."