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90 TUNNEL FIRE PROTECTION, FIRE FIGHTING, More discussions on fixed fire suppression systems is pro- AND INTERNATIONAL STANDARDS vided in chapter twelve of this report. REQUIREMENTS Tunnel fire protection standards requirements are summa- TUNNEL FIRE DETECTION, NOTIFICATION, rized based on the literature review conducted for this report. AND INTERNATIONAL STANDARDS REQUIREMENTS A tunnel fire is more effectively fought in its early stages. Fire-detection systems are necessary to alert tunnel operators Some vehicles using the tunnel may carry fire fighting equip- of potentially unsafe conditions. The fire-detection principles ment; however, if such equipment is unavailable or insuffi- are based on the parameters determined by the fire: cient then fire fighting equipment installed in the tunnel can be used. There could be cases when the installed equipment Smoke is insufficient to manage the fire size. Therefore, equipment Heat such as fire hydrants and fire hose valves are used by the fire Flames (radiation). department. There are a range of methods available to detect fire and Generally, hand-held extinguishers are provided in the smoke within road tunnels, including linear (line-type) heat tunnels; however, the required distances between them vary. detection, closed circuit television (CCTV) video image Pressurized fire hydrants or fire hose valves are provided for smoke detection, flame detection, smoke and heat detectors, most tunnels. and spot-type heat and smoke detection. Selections of fire- detection systems are made depending on the fire safety goals Appendix F2 (web-only) provides comparison tables and objectives and the overall fire safety program. This includes notifying occupants to allow for safe evacuation, on tunnel fire protection requirements in different national modifying tunnel operations, initiating a fire life safety sys- (including NFPA 502, 2008 edition) and international stan- tems operation, and notifying emergency responders. The dards. It covers the fire fighting equipment (extinguisher, key objective is prompt notification while preventing nui- hose reels, and so forth) and water requirements. Typically, sance alarms. Some jurisdictions require that "listed devices" design fire size and physical tunnel configuration drive water be used. This is a design challenge because there are few flow and pressure requirements. listed devices for tunnel application. Depending on the nature of the fire, either smoke, flame, or heat can start developing No European standards have requirements for installation first. Consequently, multi-sensor alarm systems are better of a fixed fire suppression system. Such requirements do suited for automatic control. exist in Japan and Australia: The National Fire Alarm Code (NFPA 72 of 2010), In Australia, AFAC (the Australian Fire Authorities PIARC (PIARC Technical Committee C3.3 2007, PIARC Council) strongly advocates the installation of suit- Technical Committee C3.3 2007, PIARC Technical Com- ably designed, manually controlled deluge/sprinkler mittee C3.3 2008) and several research projects provide addi- systems. tional information to assist with the development of detection In Japan, sprinkler systems are required for the following system concepts and designs. The Fire Protection Research tunnels: Class AA, Class A tunnels more than 3000 m Foundation (FPRF) of the United States and the National long and with average daily traffic of greater than 4,000 Research Council (NRC) of Canada sponsored a two-year vehicles/day, and bi-directional tunnels. Sprinkler sys- international research project to investigate available fire- tems have been installed in more than 80 tunnels in detection technology suitable for tunnel application. The Japan. main objective idea of the study was to provide information for use in the development of performance criteria, guide- In Sweden, fixed fire suppression systems would be in- lines, and specifications for tunnel fire-detection systems, stalled if it leads to a significantly raised level of safety for and to be used for updating NFPA 502. people according to risk analysis. The NRC has conducted fire tests in a laboratory facility In Korea, the Gwangju Institute of Science and Technol- and performed CFD analyses to investigate the impact of ogy (GIST) recommends installation of a fixed fire suppres- various tunnel fire scenarios on the performance of fire- sion system for tunnels that are more than 3000 m long with detection systems. They have also conducted full-scale fire traffic flow of more than 60,000 vehicles kilometers/ tests in an operating road tunnel in Montreal in collaboration day/tube for bi-directional tunnels or more than 90,000 vehi- with the Ministry of Transportation of Quebec and in the cles kilometers/day/tube for uni-directional tunnels. A Lincoln Tunnel in New York with the support of the Port sprinkler system has been installed in the Joogryeng Tunnel Authority of New York and New Jersey. One of the objec- in Korea (56). tives was to investigate the false alarm potential in a tunnel

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91 environment (57). A discussion of these methods along with fire. Considerations shall be given to a large ventilated tunnel some of the advantages and disadvantages for each system volume, which makes fire detection difficult. follows. CCTV Video Image Smoke Detection Linear (Line-type) Heat Detection Video detection is a relatively new smoke detection technol- There are several types of line-type heat detectors in use today. ogy that uses real-time video images. Through proprietary The three main types are Analog (Integrating) Linear Heat software, this technology is able to detect fires by analyzing Detectors, Digital Linear Heat Detectors, and Fiber Optic changes such as brightness, contrast, edge content, loss of Linear Heat Detectors. detail, and motion. Analog (Integrating Heat Detector) systems incorpo- Video smoke and heat detection has a number of advan- rate a multilayer cable. A core conductor is covered by tages. First, the system cameras can be used for other sys- a temperature-sensitive semiconductor with an outer tems such as traffic control monitors and security, as well as conductor. The inner and outer wires are connected smoke and fire detection. Second, detection is based on real- to a control panel that monitors the resistance of the time video images; therefore, each camera can cover a large semiconductor. A temperature rise in the cable causes area. Third, this technology is capable of detecting fires in a reduction in the conductor's resistance and detection moving vehicles. Fourth, emergency responders can be pro- occurs when the monitored resistance reaches a pre- vided with real-time video information about a fire. The visu- determined setting. als can provide useful information such as fire size, source, Digital Linear Heat Detectors consist of two polymer- and location, which can help operators and responders to insulated conductors. The insulation melts at a set efficiently react to the incident. temperature. Detection in this system occurs when the insulation melts, which allows the conductors to make Interest in the use of the automatic video image detec- contact with each other. In some systems, the control tion (VID) system for road tunnel protection has increased panel connected to the sensing element is able to deter- because of its quick response to the fire or security incident, mine the distance where the conductors made contact and real-time video images for use in monitoring events, and its determine the location of the fire. ability to guide evacuation, rescue, and firefighting. Many Fiber Optic Linear Heat Detectors consist of a control tunnels are already equipped with VID systems for traffic man- panel and quartz optical fibers. The control unit houses agement and security protection. Recent studies conducted by a laser that sends a beam through the fiber optic cable. the FPRF at NFPA also showed that the VID fire-detection sys- These systems provide detection using the Raman Effect, tem was one of most promising detection technologies for the which senses temperature changes by evaluating the use in road tunnel protection. amount of light scattered. A new generation of video detection technology is being One of the main advantages of this type of detection is that developed. It includes volume sensors; meaning that it looks the cable is suitable for harsh environments. In addition, for fire and smoke within the entire observation space of the because these products are essentially a two-conductor cable, Internet protocol (IP) address of the camera. This fundamen- there is flexibility in the installation: patterns can be used tal advantage results in faster, reliable fire and smoke detec- to meet spacing requirements and the cable can be routed tion and, most importantly, provides a visual picture of the around obstructions. Many of these products can determine situation to the on-duty operator. Some cameras are both the approximate location of the fire based on either a reduc- Underwriters Laboratory (UL) listed and Factory Mutual tion in the conductor's resistance or light scattered for fiber (FM) approved, and have flame and smoke detection devices optic systems. Some manufacturers of these systems also that are also FM approved. The cameras have passed tunnel promote the longevity of their systems; with a useful system tests in Canada, New York, and China (58). Use of camera- life of approximately 30 years. based detection systems may fulfill a multi-purpose regimen if the camera image can be used for security, traffic, and/or Disadvantages of linear heat detectors are that some road conditions as well. require cable replacement after a fire. With tunnels typically being extremely large, with long open spaces, providing To prevent nuisance alarms, multiple detections and con- detection using linear heat detection can require a large firmations are required before notification or system activa- amount of cabling. If the objective is to detect a fire from a tions can occur. This also provides redundancy in case one moving vehicle, such as a tractor-trailer, the design will need detector fails. When the alarm conditions are met the event to assess whether the cable will be heated sufficiently to actu- file is created and sent to the remote monitoring station oper- ate. There are known bus tunnel events where there was a ating the system. The on-duty operator receives the notifica- new linear heat detection system that was unable to detect tion of the alarm with live video from the location. Designers

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92 will need to review listings and approvals with the authorities Projected beam smoke detectors typically consist of a detec- to determine the suitability of these devices for specific pro- tor unit with a receiver. A beam of light is sent from the detec- jects. Because these systems rely on video imaging, some of tor to the reflector and if the beam is obstructed it will trigger them may have a difficult time in detecting shielded fires. an alarm. A disadvantage of projected beam and duct-mounted This can be a disadvantage for other systems as well. detectors is that they are prone to nuisance alarms from diesel exhaust, which is almost always present in road tunnels. Flame Detectors Appendix F3 (web-only) provides comparison tables on tunnel fire smoke detection requirements in different Flame detectors are fixed devices that are capable of sensing national (including NFPA 502, 2008 edition) and interna- fire by the amount of radiant energy that is emitted. Detectors tional standards. in this category include ultraviolet, infrared, combination ultraviolet/infrared, or multiple wavelengths infrared. In a few national guidelines for road tunnels, there are val- ues for the maximum detection time and degree of accuracy Flame detection systems have a number of advantages. of fire location, including fire loads and airflow speed. Fire- These systems typically work well in and are suited for harsh detection time is a critical element in a tunnel fire event. environments such as those found in tunnels. Some of the Detection time depends on fire development and ventilation more challenging fires in road tunnels involve combustible conditions and varies from 1 to 2.5 min. Maximum design and flammable liquid. Flame detectors are well-suited for detection time is directly related to fire development. detecting these types of fires. These devices are also capable of detecting fire signatures that include a range of varying Table 28 provides requirements for fire-detection and fire wavelengths, which provide design flexibility when devel- alarm systems in road tunnels in various countries. The fol- oping the system. lowing can be concluded from this table: A disadvantage of these systems is that historically they An alarm triggers no later than 60 s after ignition or at have been prone to nuisance alarms caused by interference fire energy load not exceeding 5 MW. from arc welding, electrical arcs, lightning, metal grinding, The fire alarm system shall respond to relatively low artificial lighting, and in some cases even sunlight. Newer energy release rates of 1.55 MW (517 MBtu/hr), designs account for these interferences. As with many of meaning that it must be capable of detecting fire at an other systems, detection can be delayed for shielded fires. early stage. Detection shall be made possible without restrictions to airflow speed in the tunnel up to 6 m/s (1,181 fpm). Spot Detection The accuracy of spotting the fire shall be between 20 and 50 m (65.6 and 164 ft). A number of traditional smoke and heat detection systems can be used to detect fires in road tunnels. These systems include the use of projected beam-type smoke detectors, duct Notification smoke detectors, and heat detectors. Once the detection system is implemented, it can be used to provide automatic notification to any or all of the following: Duct smoke detectors are provided in the tunnel ventila- motorists, tunnel controllers, external agencies (traffic), emer- tion ducts. Typically, the actual detector is mounted on gency responders, etc. the outside wall of the duct. The detector is connected to a metallic tube that extends across the duct. The tube has A combination of fixed signage (speed, lane control, rescue calibrated holes that draw air into the tube, which is then zones) and variable message signs (VMS) provide a workable directed to the detector. mix of visual instructions. The ability to use VMS as part of There are many different types of heat detectors. Typi- the preprogrammed emergency response scenario could prove cally, detection is either by an abnormally high tem- helpful by stopping or slowing traffic; instructing motorists to perature; a pre-determined temperature rise. Some heat turn off their vehicles, leave their keys, and exit; and direct detectors are capable of detecting both temperature and them to clear a traffic lane and move to the optimum exit path. rate of temperature rise. Manual controls are always used for VMS. This allows One of the main advantages for these systems is that they are incident command to communicate with emergency respon- readily available and there is a wide pool of contractors capa- ders, motorists, and others if radio communication fails. ble of installing these systems; therefore, there is no need to hire a specialized contractor. Compared with the other sys- In addition to visible notifications, AM/FM radio override tems, these systems are relatively inexpensive. is common, but less effective given the reduced use of com-