Rainfall is forecast to grow more intense in coming days as levels of carbon dioxide pose additional danger

Thai authorities believe they have a three- to four-day window to free 12 boys stranded inside a northern Thailand cave and will focus on reducing the dangers of the rescue operation as much as possible until rain or increasingly toxic air inside the chamber forces them to act.



Narongsak Osatanakorn, the governor of Chiang Rai province, said on Saturday the operation to drain water along the 3.2km path to where the boys have been sheltering for the past fortnight has been “very successful” and withstood patches of rain.

Boys trapped in Thai cave write letters telling families ‘don’t worry’ Read more

“Today it rained but the water level is still at a satisfactory level,” he said.

But rainfall is forecast to grow more intense in coming days and become torrential by early next week, giving rescuers only a few days to extract the boys and their 25-year-old coach before they could be sealed off until as late as January, he said.



“[The next] three to four days from now is the most favourable time for the operation and rescue mission using one of the action plans,” Osatanakorn told a press conference at the cave site. “If we wait too long, we don’t know how much rainwater will come.”

He said heavy rains last week had the effect of a “tsunami” inside the narrow and jagged cave network where the boys became stuck on 23 June.

No matter how much oxygen we have, we cannot survive [too much carbon dioxide] because our blood will be toxic

Two factors will determine when any rescue operation is mounted, the first the quality of the air inside the boys’ chamber. Osatanakorn had said on Friday that oxygen levels in their part of the cave had fallen to 15% – down from healthy levels of 21%.

“If the oxygen level drops lower than 12%, it will affect the brain and the people inside,” he said. “They could be shocked.”

An additional danger was the growing concentration of carbon dioxide in the cave exhaled by the hundreds of rescue workers who had been inside.



“No matter how much oxygen we have, we cannot survive [too much carbon dioxide] because our blood will be toxic.”



The second constraint is the water level inside the cave, with authorities acknowledging for the first time that the ledge where the boys are stranded may not be immune from flooding.

“From what I heard, the water can reach them [there],” Osatanakorn said. “Which could reduce the space for them to less than ten square metres.”

Rescuers would continue trying to reduce water levels until the predicted rain forced them to make a decision on guiding the boys out. “The perfect situation is no water at all, zero, but it’s impossible because that only happens in December or January,” he said.

“So we rule that out. Second best is the water level is low enough to bring them out.”

If the risk from either the air or water increased “to the point that we cannot accept, we will make decision”, he said.

“We are racing against time and shoulder all the expectations.”

The boys, whose letters to their parents from inside the cave were published on Saturday, were still in good shape.

“Today the kids are still healthy, they can talk, joke, only have some small wounds. They don’t have proper food yet but it’s special food with extra protein added to boost their energy,” Osatanakorn said.

Additional reporting by Veena Thoopkrajae