The human body works best at sea level. Oxygen levels are sufficient for our brains and lungs. Our bodies can't function at high altitudes.

The "death zone" is where climbers have to go if they want to summit Mount Everest, the tallest peak in the world at 29,029 feet. The area with an altitude above 8,000 meters has so little oxygen that the body starts to die in a matter of minutes.

Climbers' brains and lungs are deprived of oxygen, their risk of heart attack and stroke is increased, and their judgement is impaired.

A climber who summited Everest in 2005 told Business Insider that the climber's body is breaking down. The race becomes a race against time.

Most of the people who died on Everest were in the death zone. It was one of the most dangerous seasons on Everest.

The peak became so crowded with climbers that people were stuck in the death zone for too long. Many climbers had to wait in line to go up and down after 250 climbers tried to reach the summit on May 22.

The extra hours in the death zone might have increased the risk of death for 11 people.

One mountaineer said climbing Everest feels like 'running on a treadmill and breathing through a straw'

traffic jam mount everest
There is a deadly traffic jam on Mount Everest as climbers are forced to wait in the "death zone."

The air at sea has 21% oxygen. Oxygen levels are lower at 12,000 feet.

According to Jeremy Windsor, a doctor who climbed Everest in 2007, blood samples taken from four mountaineers in the death zone showed they were only able to survive on 25% of the oxygen they needed at sea level.

Patients on the verge of death had similar figures.

It can feel like running on a treadmill and breathing through a straw when you're five miles above sea level.

Climbers need to acclimate to the lack of oxygen

There are health risks associated with a lack of Oxygen. If your heart rate goes up to 140 beats per minute, you are more likely to have a heart attack.

Climbers have to acclimatize to the lung-crushing conditions in the Himalayas before attempting to summit Everest. Each expedition makes at least three trips up the mountain from Everest Base Camp, which is higher than nearly every mountain in Europe at 17,600 feet.

After a few weeks at high altitudes, the body starts to make more hemoglobin in order to compensate for the lack of oxygen in the air. Too much hemoglobin can make it harder for the heart to pump blood. That can cause fluid in your lungs to build up.

A stethoscope can reveal a clicking sound as fluid leaks into the lungs on Everest. fatigue, weakness, and a persistent cough that brings up white, watery, or frothy fluid are some of the other symptoms. Sometimes the coughing is so bad that it can cause serious injury.

When resting, climbers with HAPE are short of breath.

In the death zone, your brain can start to swell, which can lead to nausea and a form of psychosis

It's not possible to adjust to death-zone altitudes, according to high-altitude expert and doctor Peter Hackett.

Hypoxic, a lack of oxygen to the brain, is one of the main risk factors. It's meant for the brain.

It can cause nausea, vomiting, and difficulty thinking.

A form of high-altitude psychosis can be caused by an oxygen-starved brain, which can cause climbers to forget where they are. Hypoxic climbers have been known to do strange things, such as talking to imaginary friends, when their judgement is impaired.

Other possible dangers include insomnia, snow blindness, and vomiting

climbing everest
When climbing in the "Death Zone," your brain receives one-quarter of the oxygen it needs.
Lhakpa Sherpa

She said that your body gasps for air and you wake yourself up.

She couldn't sleep due to the thin air.

The human will start to get old. It becomes a problem when you sleep. There is a process of muscle wasting. Losing weight takes place.

A decrease in appetite is caused by nausea and vomiting from altitude related illnesses. Snow blindness can be caused by the glare from the snow and ice.

The temperature in the death zone never goes above zero degrees. Burke said that any exposed skin would freeze immediately.

Gangrene can be caused by a lack of blood circulation to climbers' fingers and toes. Tissue that is gangrenous needs to be removed.

Accidents can be caused by weakened vision and physical weakness. Burke says that fatigue is always present.

She said it took everything to put a foot in front of the other.

Poor decision-making can lead to climbers forgetting to clip back into a safety rope, straying from the route, or failing to prepare life-saving equipment like oxygen tanks.

Mountaineers climb through the death zone in a day, but they can wind up waiting in line for hours

lhakpa sherpa at the top of everest
Climbers can only spend 20 minutes on Everest's summit before having to descend.
Lhakpa Sherpa

David Carter told PBS that climbing in the death zone is a living hell.

Climbers attempt to bag the summit in a single day, spending as little time as possible in the death zone before returning to safer altitudes. The push to the finish line comes at the end of the climbing season.

The most difficult part of the trek is the day a group attempts to summit Everest, according to Lhakpa.

Everything must go right to be successful. Climbers leave Camp Four around 10p.m. The first part of their climb is done in darkness.

Climbers usually reach the summit within seven hours. After a brief rest filled with celebrations and photographs, the expeditions return to safety and arrive before the sun goes down.