In more detail, Notre Dame's new fire protection system rests on five pillars.

    The first is surveillance. “In addition to thermal cameras, an air suction and analysis system will be in constant operation,” explains the public institution in charge of restoring Notre Dame of Paris. “Any outbreak of fire detected by at least two pipes will automatically trigger the misting system.”

    The system will release a mist consisting of fine droplets of water diffused into the wooden framework, which, if necessary, will considerably reduce the temperature in the space and smother the incipient fire.

    The third pillar is the thickening of the batten: the thin planks of wood that separate the trusses from the lead roofing. “One millimeter thick has a fire resistance of one minute: We added 15mm [0.6”, editor’s note], giving the fire a quarter of an hour less chance of spreading to the roof,” explains the company.

    Fire-stop trusses have been installed to separate the spire from the choir on one side and the nave on the other. They divide the space in three, preventing or delaying the spread of fire from one to the other.

    Finally, the entire network of dry columns has been redesigned to facilitate firefighting operations. The flow of water that can be mobilized has been multiplied by three to reach up to 600m3 (264 gallons) of water per hour.