Performance of water-based fixed fire fighting systems in road tunnels: A review

A review concerning the development and performance of water-based fixed fire fighting systems (WFFFS) in road tunnels is presented. Conventional WFFFS types, including automatic sprinkler system, deluge system, and water mist system, have gained recognition as valuable supplements to ventilation systems in combating tunnel fires. Full-scale projects through international collaborations have been instrumental in formulating guidelines for facilitating the installation and optimal functioning of WFFFS in road tunnels. Extensive small-scale experiments, along with numerical investigations documented in literature, greatly contribute to complete exploring the performance of WFFFS. Owing to these efforts, advantages of WFFFS, such as reducing fire size, cooling hot smoke, and limiting smoke spread are well affirmed, and the shed mechanisms behind these fire fighting effects now have been well understood. However, WFFFS also present challenges from aspects such as disrupting smoke stratification and augmenting the production of toxic combustion products. From the review, further development of WFFFS in road tunnels relies on establishing methods of specifying design fires that accounts for suppression effects of WFFFS, as well as gaining deeper insights into the cooperative and interactive mechanisms between WFFFS and mechanical ventilation systems.