smoke control, response management, ventilation
Ventilation in tunnels is required for normal and emergency operation. During normal operation, its purpose is to provide a clean air environment and to maintain reasonable temperatures during congested conditions. During emergency operation, ventilation is needed to influence the flow of smoke and combustion products so as to create a safer environment for tunnel users to escape and for emergency services to intervene. This document presents a guide to tunnel ventilation systems and their operation during emergency conditions. The emergency ventilation system design requires the identification of the potential fire and smoke threat in terms of visibility, temperature and toxicity effects. Therefore, given the layout of the tunnel, the designer has to consider the characteristics of the traffic (expected flow, type of vehicles and combustible load); the means to safeguard tunnel users by keeping a smoke-free area and providing sufficient exit facilities for egress and rescue, and to support the responding emergency services; the minimum ventilation and/or extraction capacity to cope with the design fire scenario; other safety facilities such as egress routes, doors, passageways, and various equipment (video cameras, phone facilities, fixed fire suppression systems, fire extinguishers and communication circuits); meteorological conditions between the portals that may create, through pressure difference, very important natural air flow velocities inside the tunnel.
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