Time is running out for those still trapped under the rubble in Turkey and Syria following the 7.8-magnitude earthquake that struck regions of both countries on Monday.
National and international rescue teams are working tirelessly to remove debris wherever there is a sign of life.
Look: Why is aid to Syria so much more difficult than to Turkey after the earthquake?
But how long can you survive under the rubble?
That depends on several factors, according to experts who spoke to the BBC. The position in which the survivor is after the collapse, access to air and water, the climate, the weather conditions and the physical state of the trapped person all influence how long they can stay alive.
The United Nations typically concludes its search and rescue efforts five to seven days after the disaster. That decision is made if two days have passed without any bailout.
Most successful rescues happen in the first 24 hours of the disaster.but there have been cases where people have been pulled out of the rubble alive after much longer.
In May 2013, for example, a woman was pulled alive from the rubble 17 days after a factory collapsed in Bangladesh.
And after the earthquake in Haiti in 2010, which left at least 200,000 dead, a man was rescued after 12 days from the rubble of a store.
So what are those factors that can keep victims alive?
oxygen and water
There are different factors that play a crucial role for a person to survive.
"In collapsed buildings between the cement or concrete plates there will be gapsspaces in which people can survive, and that explains why the rescue teams continue their work," Ray Gray, who for three decades participated in rescues with the British NGO International Rescue Corps, told BBC Mundo.
Gray has been to earthquakes in Afghanistan, Iran, Honduras and Colombia, among other countries.
A key element is access to oxygen.
"Oxygen is generally not a problem in a collapsed building because the air finds its way in"Grey said.
The next essential factor is access to water.
"When a building collapses, fire alarms usually activate water sprinklers. The gas and electricity supply will have been cut off in the building to prevent explosions or fires, but the water supply remains because fluid may continue to leak from broken pipes".
"I've been on rescues where firefighters spray the debris with water so it can drip down and reach trapped people."
Roberto Rubio is the founder of the NGO Salvamento, Ayudad y Rescate, SAR-NAVARRA-ESPAÑA (international aid entity), and has led rescues in cases of earthquakes and other disasters for two decades, in places like Haiti, Chile, Ecuador, Peru, Iran and Turkey.
Rubio told BBC Mundo that the factors that affect survival in these situations they are unpredictable. "But just like the rescuers there, hope cannot be lost until the end."
"The main survival factors in a trapped person so that they can be rescued alive are undoubtedly the injury severityboth those that occur at the time of the collapse, as well as previous pathologies," said Rubio.
"In many situations, the people rescued alive after 10 days are young people with no previous pathologies of interest."
In addition to access to oxygen and water, other factors to take into account are "the permeability of the rubble, the quality of its fracture structure, which also affects both survival and rescue. For example, the morphology of plates, big or small, clean or dusty".
Rubio added that Temperature is a very important factor to take into account.since the local climate determines how much the victims can resist.
"This factor significantly reduces the survival rate by causing dehydration of the trapped, but it is the temperature of the place where the victim is that really makes the difference."
According to Professor Richard Edward Moon, an expert in intensive care at Duke University, United States, winter conditions in Turkey worsen the situation.
"A typical adult can withstand temperatures of up to 21C without the body losing its ability to retain heat. But when it gets colder, things change," he said.
In that instance, the body temperature essentially follows the ambient temperature.
"The speed at which hypothermia occurs will depend on how isolated the person is, or how much protection they have. In the end, many of the less fortunate will have hypothermia under these circumstances," says the specialist.
In the summer, the opposite happensIf the environment is too hot, the victim may become dehydrated too quickly, reducing their chances of survival.
Even if a person is found alive, they can face serious problems due to the so-called crush syndrome or crush syndrome.
"The Crush Syndrome It is a necrosis or death of the muscles due to a compression of any cause, for example, a person who can get his leg trapped in an accident of agriculture, or of a machine, or generally in a collapse, the typical example is an earthquake or the fall of a building", explained to BBC Mundo Dr. José Luis Górriz, president of the Valencian Society of Nephrology and head of the service of the Hospital Clínico Universitario de Valencia.
"So by compressing the muscles, especially in the legs, ischemia occurs, they lack blood supply, inflammation occurs, and this inflammation and lack of blood supply can cause muscle death, cell death."
Cell death causes toxic substances to be released into the bloodstreamwhich can cause two serious complications, noted Dr. Górriz.
"One is that fragments of a part of the muscle called myoglobin block the renal tubules, as if they obstructed the urine formation pipes and that induces the patient to urinate less or stop urinating. So you have to unclog that somehow with drips (physiological serum) or with fluids".
"Second, as the cell becomes necrotic, the muscle cells and other cells, and 90% of the potassium It is inside the cell, then it leaves the cell into the bloodstream, into the blood, and there is a very significant elevation of potassium that can cause an arrhythmia and death."
The rescue of survivors must therefore be extremely careful.
"You have to put drips to increase the perfusion volume, increase the amount of blood in the vessels, so that it acts as a kind of unblocking."
"If that kidney does not recover with drips immediately, it would need dialysis and may even be left with permanent kidney failure. In general, recovery through IV drips or dialysis is usually associated with a good prognosis in the short or medium term if action is taken quickly."
"But then there is another problem that the doctors face and that is that when the patient is removed from the rubble, there is a lot of added danger, because when they remove him all those substances that were compressed by the rubble are released into the blood and make a toxicity phenomenon.
“They must come back again and again”
Gray says that because of the complexity of the rescue, it can't move quickly, or it would increase the risk of debris endangering trapped people who may still be alive.
Forks It is essential that rescuers return to the same location multiple times.
"Rescuers need to go back to the same spot over and over again to make sure they didn't miss picking up signs of a trapped person who was asleep or unconscious the first time they were there."
A factor that is often underestimated, according to experts, is well-being and mental control.
They point out that the The ability to maintain a focused will and survival mindset can also be crucial. in staying alive.
“Fear is our natural reaction, but we should not panic. We need to be mentally strong in order to survive,” advises Murat Harun Ongoren, coordinator of AKUT, Turkey's largest civil assistance and rescue organization.
That requires determination.
“It is important to try to avoid feeling afraid and take control of ourselves. 'Okay, since I'm here, I have to find a way to stay alive' should be the motivation. That will generate less yelling and physical movement. You will have to conserve your energy by controlling your senses and panic.
Although finding survivors after several days can be extraordinary, such cases do occur.
In 1995, after an earthquake rocked South Korea, a man was pulled from the rubble after 10 days. It was reported that had survived by drinking rainwater and ate a cardboard box. She had amused herself with a child's toy to keep her mind active.
In May 2013, a woman was pulled from the ruins of a factory in Bangladesh, 17 days after the building had collapsed.
“I heard the voices of the lifeguards for several days. I continually hit the rubble with sticks and pipes to get their attention. nobody listened to me”, she declared when she was rescued.
“I ate dehydrated food for 15 days. The last two days I had nothing but water.”
In Haiti, after the January 2010 earthquake that claimed the lives of more than 220,000 people, a man survived 12 days under the rubble of a shop that had been looted. another man was found after 27 days buried under the ruins.
In October 2005, two months after an earthquake struck Pakistan's Kashmir region, a 40-year-old woman named Naqsha Bibi was rescued from her collapsed kitchen.
They found her with numb muscles and so weak she could barely speak. In conversation with the BBC in 2005, a cousin of hers said: "We first thought she was dead, but she opened her eyes when we were taking her out."