Tunnel fire protection and fire life safety are newly adopted requirements in USA and North America. In 2004 the National Fire Protection Association (NFPA) instated NFPA 502 – Standard for Tunnels, Bridges, and Limited Access Highways to include fire protection for tunnel structures. In 2008 edition the committee qualified risk assessment to be done on all highway tunnels – new and existing - for fire resistance and structural performance. The standard adopted the Rijkswaerstaat (RWS) time/temperature curve for 2 hours or other accepted fire curve to be approved by the AHJ (Authority Having Jurisdiction) after an engineering analysis is performed.
The current NFPA-502 edition 2020 states the protection of the tunnel structure must meet the following measures:
The structure shall be capable of withstanding the temperature exposure represented by the Rijkswaterstaat (RWS) time-temperature curve for a duration of 120 minutes or other recognized standard time-temperature curve that is acceptable to the AHJ following an engineering analysis to prevent irreversible damage and deformation leading to progressive structural collapse.
Tunnels with concrete structural elements shall not spall from a 2 hour/ RWS fire event which leads to progressive structural collapse and the interface temperature of the concrete shall not exceed 380°C (482°°F). The reinforcement shall not exceed 250°C (482°F) assuming 25mm (1in) minimum cover.
Tunnels made from steel or cast iron interface temperature shall not exceed 300C (572°F).
The fire protection shall be non-combustible with a minimum melting temperature of 1350°C (2462°F)
The fireproofing industries #1 focus is saving lives; this same focus is applied to tunnels to support firefighter accessibility, minimize the economic impact and mitigate structural damage including maintaining escape passages, safe evacuation, electrical, and ventilation. For tunnels under waterways it is mandatory for the tunnel to be fire protected due to the possibility of tunnel collapse causing extreme flooding preventing transportation devastation, costing repair-rebuild cost for an infrastructure owner.