Emergency! ZDA-110-3-15-1 What do you do? Every Second Counts

Emergency! ZDA-110-3-15-1 What do you do? Every Second Counts

On April 15, 2019, a fire started at Notre-Dame cathedral.

Within an hour, its famous 750 ton spire collapsed.

The cause of the fire is still unknown.

However, we do know something about the design of its fire alarm system…

As the New York Times explained:

“The fire warning system at Notre-Dame took dozens of experts six years to put together, and in the end involved thousands of pages of diagrams, maps, spreadsheets and contracts.”

The fire alarm system was a hugely expensive, highly sophisticated, complex system. It was also badly designed.

Technically, it worked. Practically, it failed.

Scott Berkun explains more in his excellent book, How Design Makes the World

“This complexity would be the cathedral’s undoing. At 6:18 p.m. on the night of April 15, an inexperienced security employee, working an extra shift to cover for a co-worker, saw a warning on the fire safety system. It first told him what quadrant of the building might have a fire in it, ‘Attic Nave Sacristy’, and then a code:


Double Rainbow What Does it Mean

Like a double rainbow what does it mean?

“It’s unclear how much of this message the guard understood. The code referred to a specific detection device, but there was no way the guard could have known how to use this code to locate the fire. The system wasn’t designed to make this easy to understand. And his job wasn’t designed with the training to close that knowledge gap. He did call the guard inside the church and asked him to investigate. The problem was that there were two attics in the cathedral, and the church guard went to the wrong one.

“It took 25 minutes, as the fire spread quietly hundreds of feet above their heads, for them to realize their mistake. By the time the church guard climbed the three hundred steps to the main attic, the fire was raging out of control. They finally called the fire department, but the damage had already been done. The fire had been growing for at least thirty minutes in total, tearing through the attic’s wooden beams and support structures.

30 minutes before the fire brigade was called.

30 minutes before the fire brigade was called!

30 minutes!

The tower collapsed in 60 minutes.

Notre Dame Cathedral Fire

Notre Dame Cathedral Fire – GodefroyParis, CC

“We like to think that, here in the present day, with almost nine hundred years of technological progress from the time the Notre-Dame cathedral was designed, failures like this would be impossible. The truth is that designing things well isn’t easy to do.”

You should read the book.

Tesler’s Law

In software, Tesler’s Law, or The Law of Conservation of Complexity, states that for any system there’s a certain amount of complexity which cannot be reduced. That does not imply however that complexity in software is a good thing, or that all complexity cannot be reduced.  In Scott’s example, the inherent complexity of the fire alarm system with its indecipherable messages, could have been designed to be much simpler and clearer. Good design makes software better, safer, more loved…

Scott Berkun at BoS Conf Online.Spring, 26-27 April 2021

In Scott Berkun’s session at BoS Conf Online.Spring, 26-27th April, he’s going to share some insights from his book and his experiences designing and building software you will have used, to help you answer the question, “Is your software as easy to use as you think?”

Needless to say, the session is designed to be useful, interactive, engaging, fun – and give you some ideas that you can put to work straight away.

“Is your software as easy to use as you think?”


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