Currently Lima, Panama and Santiago are expanding their metro lines, Bogotá is building its first line, and after several decades without building mass transit systems in Mexico, a high-speed train is being built between Mexico City and Toluca.
By Jaime A. Moncada, PE
Many Latin American capitals, 29 to be exact, already have urban rail transport systems, commonly called metro. There are large and old people, like the one in Mexico City with 200 km long, almost five million daily users and 50 years of use. There are small and more modern ones, like the one in Panama City, with 16 km in length, 260,000 daily users and inaugurated in the 2015.
Two of the ten fires with the most deaths worldwide, since the beginning of the 21st century have occurred in meters or passenger trains, fires that we will discuss later and that highlight the importance of fire safety in railway systems. NFPA 130, Standard Guide Rail System for Passengers and Passengers (Standard for Fixed Guideway Transit and Passenger Rail Systems), establishes the security criteria against protection in this type of facilities.
Fire in the Daegu Metro
The 18 of February of 2003, to the 9: 53 am, a mental patient tried to commit suicide while traveling as a passenger in the subway of Daegu, subway that serves the fourth largest city of North Korea. This mental patient threw on his body part of the contents of a four-liter bottle of gasoline and tried to catch fire. The passengers around him tried to avoid this tragedy, but the gasoline that had spilled on the floor caught fire.
Fortunately, at that time the train stopped at Jungagno station, one of the busiest in this city of 2,5 million inhabitants. Most of the occupants of the train were able to escape, including the mentally ill. However, the interior finishes of this train, which was composed of five wagons, were combustible and the fire spread with great speed. At the 9: 55 am, another train, also with five wagons and full of passengers, coming from the opposite direction to the first one, stopped at the parallel platform of this station.
The train opened its doors, but the driver, seeing that the station was filling with smoke, closed the doors, while he called the central station explaining what was happening and asking permission to move outside the station. At the 9: 57 am this second train lost power flow and could never reopen its doors. 79 people died inside the second train.
The Jungagno station is part of the # 1 line of the Daegu subway. The line is almost totally underground, part of a tunnel of 23,5 km in length. The two platforms of the station where this fire occurred were located on a third subsoil. Above the station, and without fire breaks, was a two-level shopping center, in the subsoil 1 and 2.
The mall had automatic sprinklers, detection systems and smoke control systems. However, the subway platforms were not protected by sprinklers or smoke extraction. The fire spread through the platforms and the rest of the shopping center, through the innumerable openings of the building, eventually claiming the lives of 192 people and wounding 148, one of the greatest tragedies in meters in recent times.
The use of this standard in this fire would have, at a minimum, substantially limited the impact of these fires. For example, the station in Jungagno would have been designed in a much more secure way, if Chapter 5 of the NFPA 130 had been used. This chapter establishes the criteria for emergency lighting, protection with sprinklers, ventilation, protection with hoses and extinguishers, evacuation and interior terminations of the station. But the article 8.4.1 would have had an even more important impact in this fire, because it establishes the criteria of protection against the ignition and inflammability of the materials that a wagon contains.
Fire of the Train in Kaprún
A few years earlier, in November 11 of 2000, at the start of the ski season in the Alps, on a train in Kaprun, Austria, with 161 passengers, mostly skiers, started a small fire. Approximately at 9: 02 am, just a few meters after leaving the station, an oil-hydraulic line, passing over a heater, in the back of the train failed, began to drip and caught fire. The passengers in the last car noticed the fire, but the train had no intercommunication with the driver's cabin, no emergency brake, no smoke detection, no fire extinguishers.
Only two minutes after leaving the station, the train entered a tunnel of 3,2 km in length with the intention of ascending 1500 m towards the top of a ski field. Upon entering the tunnel, the passengers lost cellular service, preventing them from notifying what was happening to them. At the 9: 05 am, 600 m inside the tunnel, the train stops automatically, due to the loss of the hydraulic-oil system, but the driver did not understand why this was happening and he was still not aware of the fire, which continued to grow in the back of the train. The passengers who were near the fire could not evacuate the train because neither the doors or windows of the wagons have levers of internal emergency opening.
When the train driver finally became aware of the fire, at 9: 08 am, he almost simultaneously lost communication with the control center. At the 9: 11 am, passengers in the last car could break a train window, but unfortunately this is too late for the rest of the train occupants. Only twelve people, all in this last car, survive, evacuating down the tunnel. In total 161 people lose their lives, including two people on a train that was coming down the same tunnel in the opposite direction and a person who was at the mouth of the tunnel, a couple of kilometers above the start of the fire.
The train in Kaprún, if it had been designed according to the NFPA 130, would very likely have resulted in a very different situation. NFPA 130 requires, for example, that all equipment that may offer an ignition risk must be isolated from other combustible materials. NFPA 130 also requires that each car has two escape routes, and that these evacuation routes can be operated internally without special tools. If any of these requirements, as well as many others that include this NFPA standard, have been met, this tragedy could have been avoided.
The NFPA 130 standard establishes design criteria for the design of the stations, the train line, and the tunnels. It establishes criteria for the evacuation system, fire extinguishing systems, detection and alarm systems, extraction systems and smoke management, among others. The rule gives the possibility that the design of the wagons follow pre-established prescriptive criteria, where the combustibility of the wagon and its contents have been limited, following specific laboratory tests. However, the standard allows for an engineering analysis, that is, using design for performance or performance, instead of following prescriptive requirements. This possibility, increasingly common in NFPA regulations, creates very complex problems, specifically in wagons, for the competent authority. It is complicated because it requires that those who execute the revision have experience and expertise in fire protection engineering, and that the designer documents the design process for performance very well.
Third Party Review
In cases where the competent authority requires it, due to the complexity of the design, the NFPA regulation allows the Third Party Review. Under this methodology, the design may be acceptable as long as it goes through a third-party review, specifically another fire protection engineering firm, outside the design process, which due to its experience and expertise can make a much more accurate review than what the competent authority could do. We must remember that this type of project is carried out very rarely in the same jurisdiction, so the local authority does not have specialists who can review this type of project. Specifically, the evacuation system, the extraction of fumes and the combustibility of the wagons are subjects that are difficult to review.
Fire Systems in Vagones
The main source of fire is passenger cars. In existing meters, it is very difficult to comply with the reference regulations, so a possible strategy is to limit the fire, and therefore smoke production, by installing active suppression systems in the wagons. For example, in the Madrid Metro and several trains in the US. The wagons have been protected with water mist systems.
We might think, for example, that the installation of an automatic fire suppression system inside the car in Daegu would have limited the impact of the fire. However, it is very easy to say, but very complex to implement it. Any fire suppression system in a train car has to be self-contained, and this creates complex and costly implementation problems. Gas-based suppression systems have the problem that when the doors of the car have been opened, the gas can escape and there could be re-ignition. The automatic sprinklers would extinguish without any problem the type of fires that could occur in a wagon, but their size and weight would make them almost impossible to implement.
The nebulized water system, however, uses water at very high pressure, discharged into the fire through automatic nozzles with very small orifices that "nebulize" the water. Consequently, the amount of water required to extinguish the fire is much less than with an automatic sprinkler system. When you need a small tank of water and a pipe with small diameters, it becomes an optimal option for this type of vehicle. By the way, the design standard of these systems is NFPA 750, Standard for Water Misting Fire Protection Systems (Standard for Water Mist Fire Protection Systems).
Fires like Kaprun and Daegu offer important lessons from which we can learn and improve, but it is fire safety standards, such as the NFPA 130, that have meticulously established minimally acceptable criteria so that tragedies like these do not recur. This type of project brings important challenges not only for the designers, but for the competent authority. The third-party review offers a pragmatic solution to this problem.
* Jaime A. Moncada, PE is a director of International Fire Safety Consulting (IFSC), a fire protection engineering consulting firm based in Washington, DC. and with offices in Latin America. He is a fire protection engineer graduated from the University of Maryland, co-editor of the NFPA Fire Protection Manual, former vice president of the Society of Fire Protection Engineers (SFPE), who led the development programs through 15. professional of the NFPA in Latin America. Ing. Moncada's email is firstname.lastname@example.org.