Failure to Address Challenges

PARIS — The architect who oversaw the design of the fire safety system at Notre-Dame acknowledged that officials had misjudged how quickly a flame would ignite and spread through the cathedral, resulting in a much more devastating blaze than they had anticipated.

The system was based on the assumption that if the cathedral ever caught fire, the ancient oak timbers in the attic would burn slowly, leaving ample time to fight the flames, said Benjamin Mouton, the architect who oversaw the fire protections.

Unlike at sensitive sites in the United States, the fire alarms in Notre-Dame did not notify fire dispatchers right away. Instead, a guard at the cathedral first had to climb a steep set of stairs to the attic — a trip Mr. Mouton said would take a “fit” person six minutes.

Only after a blaze was discovered could the fire department be notified and deployed. That means even a flawless response had a built-in delay of about 20 minutes — from the moment the alarm sounded until firefighters could arrive and climb to the attic with hundreds of pounds of hoses and equipment to begin battling a fire. ...
“I was stunned by the speed with which the oak in Notre-Dame burned,” Mr. Mouton said. “Oak that old can’t burn like a match. It’s absolutely incomprehensible.”
But fire safety experts said that Mr. Mouton and his team underestimated the risk — and that the fire response they designed was far too slow to fight a blaze in time.

“It doesn’t make any sense,” said Jonathan Barnett, a fire safety authority at Basic Expert in Australia. ;:“Twenty minutes is a huge delay before you get people involved. Once that heavy timber starts to burn, you can’t put it out. So I have no idea why they built in this delay.”
François Chatillon, a senior architect involved in numerous restorations of France’s historic monuments, also stressed that the intense fire risk in the oak timbers underneath Notre-Dame’s lead roof was well known. ...
For him the surprise was not that Notre-Dame burned this week, but “that it didn’t burn before.” ...
Still, fire experts said that two of the top officials on the project, Mr. Mouton and a former firefighter, Lt. Col. Régis Prunet, appeared to have miscalculated what was needed to protect such an unusual, complex and irreplaceable building from a fire.

Scientists consulted by The New York Times said fire dynamics indicated that, while the dense timbers may take time to burn completely, a fire would naturally race across the original timbers at Notre-Dame. It was a mistake to assume otherwise, they said. ...
There was no proper fire protection plan in place, not even a plan to evacuate tourists or worshipers in case of a blaze, Mr. Prunet said in a separate interview. It was a miracle that nothing had happened before, he said.... ...
Mr. Mouton said he performed a trial of the time it took for a guard to investigate an alert, racing one of his guards to the top of the attic.

‘‘It does take a certain amount of time, including for someone who is very fit,” he said. “That solution seemed reasonable to me, considering that it’s old oak and doesn’t burn like that.”
Beyond that assumption, the alert system appears to have been flawed, too, beginning with the response to the first alarm at 6:20 p.m.
The guard, seeing no obvious fire, gave the all-clear and came down.

But when an alarm goes off, it is imperative to identify which alarm it was — and why — including whether a malfunction or an insect crawled into the apparatus, said Glenn Corbett, an associate professor of fire science at John Jay College of Criminal Justice in New York City.

“There wasn’t an adequate investigation of that first alarm,” Mr. Corbett said. “That was probably the biggest mistake they made.”

At that point, presumably, a smoldering fire somewhere in the attic had begun to spread.... ...
Fire safety experts struggled to understand how Mr. Mouton came to believe that fire would spread slowly in old hardwood.

Mr. Corbett said that in long-discredited lore, fires in heavy timber buildings dating to the 19th century were sometimes referred to as “slow burning.”''

Mr. Barnett, the Australian expert, underscored that the time it takes a fire to burn a piece of thick timber completely is entirely different from calculating how quickly a fire will spread. ...
“We could have avoided all this with a modern detection system,” said Guillaume Poitrinal....
Fire alarms in France never automatically alert the fire department, a spokesman for the Paris Fire Brigade confirmed.
- Katrin Bennhold and James Glanz, Notre-Dame’s Safety Planners Underestimated the Risk, With Devastating Results, NYT, April 19, 2019

To the Editor:
Re “Pilots Followed Boeing Checklist Before Crashing” (front page, April 5):
Sensor failure is one of the most common causes of accidents. In the power and chemical industries, the following control strategy has reduced the number of such accidents a hundredfold.

For all critical measurements, we use three sensors employing different principles for their operation, and whenever the reading of one disagrees with the other two, it is disabled, while the system continues operation using the average reading of the remaining two detectors.

Whenever this occurs, the operator is alerted, and the computer automatically releases the system for human override.

Béla Lipták
Stamford, Conn.
The writer is the editor of the Instrument and Automation Engineers’ Handbook.
- The Mechanics of Averting an Air Crash, NYT, April 10, 2019

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