I think it is important to clarify the terms used in the debate on the use of sprinklers in tunnels (NCE 7 December).
Sprinklers are the automatic fire suppression systems that we are all used to in buildings and do not use vast volumes of water. There is a strong recommendation by PIARC against their installation in tunnels.
In practice such systems have been shown to kill people and there is a famous case in Japan of a vapour explosion killing fire-fighters after the fire had been extinguished.
The Australian approach on the other hand has been to use a deluge system. This is a high volume system used only after the tunnel has been evacuated and only by manual operation.
The Swedish solution used on the Stockholm ring road, which was established after a very long and thorough research project, is a deluge foam water system. The foam concentrate is added at each valve station. The definitive paper is by Magnus Arvidson.
David Caiden (F) firstname.lastname@example.org