Guidelines for Emergency Ventilation Smoke Control in Roadway Tunnels (2017) / Chapter Skim
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16 Road Tunnel Fires 2.1 Main Design Fire Parameters The design fire parameters used for the design of tunnel emergency ventilation and fire life and safety systems have a significant impact on the tunnel design and users' safety. The key criteria are the fire size, heat release rate, fire growth/ decay rate, smoke production, resultant temperatures, and fire duration.
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17 • Fully Developed Phase -- Nominally steady ventilation or fuel-controlled burning • Decay Phase -- Declining fire severity • Extinction Phase -- Point at which no more heat energy is being released When there is a fire that involves new types of energy carriers, it can lead to explosions (BLEVE) with catastrophic consequences.
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18 • Additional considerations are to be given to the impact of the FFSS on smoke stratification and visibility. The design process may expect the ventilation and fire safety design engineer to consider the following questions to come to a decision on the fire scenario and design fire parameters for ventilation and other fire life safety system's design: • The chart in Figure 2.1 presents a simplified process and is used for considerations of the design process only.
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From page 19... ...
19 general, the larger the fire size the more combustion products the fire produces and hence, more air is required to control smoke and hot gases. However, this ratio is not linear.
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20 density flows. There is a correlation between the local temperature; the gaseous composition (CO, CO2, O2, etc.)
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21 volumes, it is necessary to know the smoke temperatures. The theoretical stoichiometric combustion temperature of regular gasoline is about 2000°C (3632°F)
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From page 22... ...
22 Tunnel fires significantly increase the air temperature in the tunnel roadway and in the exhaust air duct (if utilized in the design)
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