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130 GLOSSARY Accident--An incident followed by the development of Flammable and Combustible Liquids Code, and a Reid unsafe situations for people in a tunnel. vapor pressure that does not exceed an absolute pressure Alternative fuel--A motor vehicle fuel other than gasoline of 40 psi (76 kPa) at 100F (37.8C), as determined by and diesel. ASTM D 323, Standard Test Method for Vapor Pressure Backlayering--The reversal of movement of smoke and hot of Petroleum Products (Reid Method). Flammable liquids gases counter to the direction of the ventilation airflow. are classified according to Section 4.3 of NFPA 30. Combustible--Capable of undergoing combustion. Flashover--A sudden transition from localized to generalized CCTV--Closed circuit television. burning where all of the items inside a vehicle or compart- Combustible liquid--Any liquid that has a closed-cup flash ment ignite. point at or above 100F (37.8C), as determined by the Heat release rate (HRR)--The rate at which heat energy test procedures and apparatus set forth in Section 4.4 of is generated by burning expressed as Btu/s or megawatts NFPA 30, Flammable and Combustible Liquids Code. (MW). Combustible liquids are classified according to Section 4.3 Length of tunnel--The length from face of portal to face of NFPA 30. of portal that is measured using the centerline alignment Critical velocity--The minimum steady-state velocity of the along the tunnel roadway. ventilation airflow moving toward the fire within a tunnel Point of safety--An exit enclosure that leads to a public way or passageway that is required to prevent backlayering at or safe location outside the structure, or an at-grade point the fire site. beyond any enclosing structure, or another area that affords Deluge system--An open fixed fire fighting system acti- adequate protection for motorists. vated on a zone-by-zone basis. Operation can be automatic Road tunnel--An enclosed roadway for motor vehicle traffic or manual. with vehicle access that is limited to portals. Fire emergency--The existence of, or threat of, fire or the Scenario analysis--The analysis of the consequences of a development of smoke or fumes, or any combination wide range of accidents in a tunnel. thereof, that demands immediate action to correct or alle- Self-rescue--People leaving the hazardous area or danger- viate the condition or situation. ous situation without the help of trained or professional Fire growth rate--Rate of change of the fire's heat release. rescuers (tunnel personnel or fire fighters). Fire suppression--The application of an extinguishing Standpipe system--An arrangement of piping, valves, hose agent to a fire at a level such that open flaming is arrested; connections, and allied equipment installed in a building or however, a deep-seated fire will require additional steps to structure, with the hose connections located in such a man- assure total extinguishment. ner that water can be discharged in streams or spray patterns Fixed water-based firefighting system (or fixed fire through attached hoses and nozzles, for the purpose of extin- suppression system; FFSS)--A system permanently guishing a fire, thereby protecting a building or structure and attached to the tunnel that is able to spread a water-based its contents in addition to protecting the occupants. extinguishing agent in all or part of the tunnel. Tenable environment--An environment that supports Flammable liquid--Any liquid that has a closed-cup flash human life for a specific period of time. point below 100F (37.8C), as determined by the test pro- Water mist systems--Fixed fire fighting systems that oper- cedures and apparatus set forth in Section 4.4 of NFPA 30, ate by discharging very small droplets of water.