PARIS – The architect who overseen the design of the fire protection system in Notre-Dame admitted that the officials had misjudged how quickly a flame in the cathedral would ignite and spread, leading to a devastating fire when they had expected. 19659002] The system was based on the assumption that the old oak timbers in the attic of the cathedral would burn slowly, leaving enough time to fight a fire, said Benjamin Mouton, the architect who oversees fire safety.
Unlike Sensitive Locations In the United States, the fire alarms in Notre-Dame did not immediately alert the fire department. Instead, a guard at the cathedral first had to climb a steep flight of stairs to the loft, a journey that Mr. Mouton would have found "fit" for six minutes.
Delays proved devastating.
"I was stunned by the speed with which the oak burned in Notre-Dame," Mr. Mouton said. "The old oak tree can not burn like a match. That is completely incomprehensible. "
But fire experts said Mr. Mouton and his team underestimated the risk – and that the fire response they designed was far too slow to fight a fire in time.
Make sense," said Jonathan Barnett , Basic Authority Fire Safety Authority in Australia. "Twenty minutes is a big delay before you involve people, so once the heavy wood starts to burn, you can not extinguish it, so I have no idea why they built in that delay . "
François Chatillon, a senior architect involved in numerous restoration work on France's historic monuments, also emphasized that the high fire risk in the oak beams was well-known among the musical staff.
After lighting, he said:" It's like throwing a match into a matchbox, you can not turn it out. "
For him, the surprise was It's not that Notre-Dame burned this week, but that it was not burning before. "
Mr. Mouton and his team were not alone responsible for all the decisions made to secure such a valuable monument as Notre Dame. At least their plans had to be approved in the Ministry of Education. Charlotte Hubert, who heads the same group of chief architects responsible for historic monuments to which Mr Mouton belongs, emphasized that the security of such buildings was strictly regulated.
"The key architects are not handed the keys and they can do exactly what they want," said Hubert.
However, fire experts said that two of the project's top officials, Mr. Mouton and a former firefighter, Lieutenant Colonel Régis Prunet, misjudged what was needed to protect such a strange, complex and irreplaceable building from a fire the dense woods may need some time to burn completely, of course, a fire at Notre-Dame would race over the original woods. It was a mistake to assume, they said.
Mr. Mouton was the responsible architect of Notre-Dame between 2000 and 2013, and in this role supervised the redesign of fire safety.
"The question of fire safety was raised immediately upon my arrival," he said. "I mastered the problem from start to finish."
Mr. Prunet, the former firefighter, became fire adviser in the Ministry of Culture and worked with Mr Mouton and his team.
The two men faced a monumental task. There was no proper fire plan, not even a plan to evacuate tourists or worshipers in the event of a fire, Mr. Prunet said in a separate interview. It was a miracle that nothing had happened before, and "a great irony" that it would happen so soon after a plan was introduced.
Both Mr. Mouton and Mr. Prunet said they have a free hand to design the most effective fire protection system. Money was not an issue.
When the budget turned out higher than expected, the authorities found the money and merely extended the number of years to implement the plan, from four to two, Mouton said.
"The project was not scaled down for financial reasons, I can absolutely guarantee that," he said.
But even if no expense was spared, there was also a conservative approach to preserve the historic wood structure in its unadulterated form. The designers were determined not to change the attic with protective measures such as sprinklers or firewalls.
The willingness to sacrifice its original state for a compromise between what was possible 850 years ago and today's reasonable, could have saved the tower, experts
The firewall technology was elsewhere in the cathedral used – but not in the attic. Mr Prunet said that the scale and complexity of the roof structure in Notre-Dame was of a different order.
"It was very complicated in Notre-Dame because the oak beams were interlocked in what we call the forest. Mr. Prunet said.
But the main reason for deciding against firewalls, Mr. Mouton said, because he could "maim" the structure.
"It's true," he said, the idea had been floated back then, "but it was discarded."
"It changes the look, but also the elements, because the wood has to be cut to set up a partition, it maims," Mouton said.
Prunet added that sprinklers were not added because they would "drown the entire structure."
Instead, the team has set on prevention and detection. This was a conscious decision.
Two guards were on-site to monitor the fragile roof structure day and night like a vault. The cathedral was covered with smoke and heat sensors. Someone went up three times a day to see if the system worked.
Mr. Mouton said he had a lawsuit against the time a security guard needed to investigate a warning and ran into the attic with one of his guards.
"It takes some time, even for someone who is very fit," he said. "This solution seemed reasonable to me, considering that it is old oak wood and does not burn so."
Apart from this assumption, the alarm system seems to have been faulty, starting with the response to the first alarm at 6 o'clock: 20:00
Since the guard saw no obvious fire, he gave the all-clear and came down.
But when an alarm is triggered, it is important to determine what the alarm is – and why – including a malfunction or an insect crawling into the apparatus, said Glenn Corbett, adjunct professor of fire science at John Jay College of Criminal Justice in New York City.
"There was no proper investigation of this first alarm," Mr. Corbett said. "That was probably the biggest mistake they made."
At that point, probably a smoldering fire had spread somewhere in the loft, although it had not yet decided how the fire started.
Fire safety experts had difficulty understanding how Mr. Mouton came to believe that the fire would slowly spread in old hardwood.
Mr. Corbett said that, in long discredited traditions, fires in heavy wooden houses from the 19th century were sometimes referred to as "slow burning".
Mr. Barnett, the Australian expert, underlined that the time taken for a fire to completely burn a thick wood is quite different from calculating the rate of fire propagation.
"He miscalculated the large surface area," Barnett said. "There is a lot of energy and it is spreading very fast."
When the second alarm sounded at 6:43 pm and a guard climbed the stairs again, the fire was already a fire.
The call finally went to the fire department at 18:51.
"We could have avoided all this with a modern detection system," said Guillaume Poitrinal, president of the Fondation du Patrimoine, an organization that promotes French architectural heritage.
The early detection technology was a suction smoke detection system provided by Siemens in 2013. However, the company stated that it had not received a service contract and that this was not possible on possible operational issues.
Fire alarms in France never alert the fire department automatically, confirms a spokesman for the Paris Fire Department.
"There may be false positives, so the firefighters are asking someone to conduct a review." said Gabriel Plus, the spokesman. He called this "elimination of doubts".
But external experts said that in the case of Notre-Dame, the decisions in fire protection design did not leave enough time for it.
There would have been another solution: permanent presence of local firefighters. Buildings that are exposed to "considerable risk" in the event of fire sometimes have such a presence, including the Louvre, the Paris Court, the National Assembly and the National Library.
Notre Dame was not in this category.
Mr. Mouton acknowledged that firefighters on standby were the only reliable way to prevent fire damage, but he said that this would not have been justified if "fires were fired all over Paris and in the suburbs."
to be adopted, he said. "All things are relative."
"I'm very worried about what happened," Mouton said.
Would he make the system different today and know what he knows now?
"The capture system would have been the same," he said, "but the response system would have changed."
"Of course the first few minutes count," he said, pausing, then added, "After the Fact is always wrong and could have been better. "