Ventilation and Suppression Systems in Road Tunnels: Some Issues regarding their Appropriate Use in a Fire Emergency

Abstract

Two important tunnel safety technologies are addressed. The majority of long road tunnels have ventilation systems. In the event of a fire in a tunnel, such systems will influence fire development in a number of different ways. Recent research and observations on these influences are presented. The effects discussed are critical ventilation velocity for smoke control and the influence of ventilation on fire size, fire spread and fire growth. There is no well defined ‘best’ approach to operate tunnel ventilation in a fire emergency. Another technology of growing importance is sprinklers and water mist systems, which are being installed in an increasing number of tunnels. There are some concerns regarding the integration of ventilation and suppression systems, these are discussed. Of particular concern is the interaction between water mist droplets and ventilation flow which may result in the suppression agent being carried long distances downstream, away from the fire. Ventilation and suppression systems should not be considered to be separate entities, but two parts of an integrated fire safety system. The paper closes with an opinion on how ventilation and suppression systems ought to be controlled to work together for fire safety.