During normal operation, ventilation, whether natural or mechanical, is required to provide a clean air environment and to prevent the accumulation of pollutants. During emergency operation, ventilation is needed to influence the flow of smoke. Smoke control plays a key role to increase the chances of survival for tunnel users experiencing a fire, in particular during the self-rescue phase.

After describing ventilation ant its essential role, the report provides a list of countries that have introduced national guidelines and points out that the European Directive 2004/54/CE places ventilation and its control (activation of ventilation in fire mode) at the forefront of minimum safety requirements for the tunnels of the trans-European road network.

Then the report describes the various types of ventilation systems commonly used in tunnels, such as longitudinal, transverse and semi-transverse systems, with or without air and smoke dampers.

Chapter 3 of the report focuses on ventilation control and describes the course of events during a fire: ignition, detection, self-rescue of tunnel users, arrival of emergency services, assisted rescue, fire fighting. In addition to the fire detection phase there are three phases that are just as crucial to the active control of ventilation: confirmation of the fire, initialization of emergency operation, and emergency ventilation conditions fully achieved.

The report also places emphasis on strategies for longitudinal ventilation and flow velocities in emergency mode to be implemented according to the type of tunnel, to the ventilation systems in place, and to the traffic level so as to optimize smoke management, and in particular prevent backlayering and maintain smoke stratification as long as possible.

The report describes the ventilation control principles in the event of a fire, from fire detection by the various sensors, to the validation process by an operator (semi-automatic or manual mode). The report addresses the various types of tests to be undertaken to confirm the reliability of the equipment and systems: factory tests, tests in situ and tests based on modelling.

In addition to many references to previous PIARC tunnel reports, the end of the report includes an English-French glossary of the main technical terms used. It also includes two annexes; one on ventilation practices adopted in several countries according to tunnel types and traffic, the other one on worldwide road tunnel guidelines.