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36 VEHICLES Transit Bus Design for Emergency Response The firefighterâs perspective provides insight into the per- ceived hazards of dealing with vehicle fires and their comfort level in responding to a fire involving a natural gas-fueled bus. A consideration of these hazards leads to the following com- ments on aspects of bus design that some firefighters believe could make an aggressive response to fires more feasible. ⢠Many buses have one or more combustible gas sensors; however, often the sensor alarm indicator is visible only from inside the bus. Arriving firefighters have a concern that the interior of a bus could contain toxic or flamma- ble gases, and therefore they may be reluctant to enter. An external indicator of the status of the methane detec- tion system gas sensors would be useful to them. ⢠PRD release points are not always easy to locate, even by someone familiar with transit equipment. A distinctive marking on the outside of the bus would help responders and others to locate them. In some cases, although the location of vents is clear, it is not clear in which direc- tion they point. ⢠Documentation (notebooks) showing the locations of important shutoff valves and switches are useful. How- ever, a symbol or legend on the vehicle itself would be quicker to use than notebooks. Figure 4 shows a bus with marked shutoff locations. If bus markings are used, the labeling should match that in printed documentation and/or training materials. Although the electrical and fuel supply shutoffs on buses are relatively accessible (though some are covered by access doors that require the use of special keys), operating these shutoffs still requires a close approach to the bus. From a fire- fighting perspective, ease of operation is important, especially if a fire is already present. At the same time, the importance of such manual fuel system shutoffs must be placed in perspec- tive. On the one hand, internal electric tank valves are more effective because they are located closer to the fuel source; on the other hand, if there is a PRD release (which cannot be reset) then a fuel shutoff valve is of little use. In any case, if the nat- ural gas fuel is not feeding the fire (and experience shows that natural gas fuel system fires are uncommon), there will not be a benefit from shutting off the fuel. Paragraph numbers are keyed to Figure 5. (3) Normally closed, electric shutoff valves that are inter- nal to the fuel tanks are useful for limiting the ability of the on-board fuel supply to feed a fire. However, currently, a responding fire crew cannot determine from visual observation whether these internal tank valves are open or closed. A visible indicator of the status of those valves is required if firefighters are to depend on the valves being closed. (5) Fires often originate in the engine compartment. If there is a fire in the engine compartment, the rate of burning is likely to be limited by the lack of fresh air in the compartment. If the compartment door is opened, the fire is likely to flare up in the face of the person opening the compartment, due to the renewed oxygen supply. A better plan would be to have a small hole in the engine compartment door into which a fire extinguisher nozzle could be inserted to get an extin- guishing agent (perhaps a dry chemical) into the engine compartment. (6) Also, from a firefighting perspective, it was suggested that there be a standpipe on the front of the bus onto which a firefighter could hook a 11/2-in. hose to get water inside the engine compartment or the passenger compartment, should that be necessary. FACILITIES Emergency procedures for transit agency facilities typically cover points such as response to alarms from combustible gas sensors, operation of ventilation fans, control of ignition sources, response to buses with fuel leaks, and fueling island failures. However, some issues remain. Topics Covered The focus of emergency procedures for facilities should be on informing the people who work in those facilities what to do in case of an emergency. Often, procedures contain infor- mation on topics such as the advantages of natural gas, the history of the natural gas fleet at that location, the cost of the equipment, the model numbers and engineering specifications of the compressor or fueling equipment, wiring diagrams, and other information that is of a background or engineering nature. The result is both to submerge the key points in a sur- feit of nonessential information and to discourage employees CHAPTER SEVEN OBSERVATIONS ON IMPROVED EMERGENCY PROCEDURES
37 procedures for transit fueling facilities should cover start-up procedures as well as shut-down procedures. OPERATIONS Driver Training There have been incidents in which the driver could have noticed that there was a vehicle malfunction that had the potential to cause a fire. For example, a substantial change in vehicle handling could be an indication of a brake malfunc- tion. Increased driver training can be of use in addressing such situations, thus reducing the number of overall incidents that have the potential to cause vehicle fires. On-Board Extinguishers In general, the first responsibilities of the driver in case of a fire incident are to park the bus safely, remove the passengers from the bus safely, and notify the appropriate authorities. In some cases, a driver or supervisor may choose to use an on-board fire extinguisher. The use of on-board extinguishers by transit agency per- sonnel raises procedural questions. If extinguishers are pro- vided, they should be of adequate size, and the driver should be trained how to use them. A recent analysis of bus fires con- cluded that if an on-board handheld fire extinguisher is avail- able for the driverâs use, it must be of adequate size to be effective (2). According to that study, 2-kg (4.4-lb) capacity extinguishers were not adequate, and a 6-kg (13-lb) capacity was the minimum useful size. with limited technical education from reading and under- standing the procedures. Shut-Down Procedures Many of the emergency procedures may be characterized as shut-down procedures. Attention needs to be given as well to start-up procedures, particularly if suspected or actual trouble was the reason for the shut-down or if repairs have been made. Experience with similar types of fuels and equipment in the chemical process industry shows that a disproportion- ate number of accidents have occurred during start-up. Thus, FIGURE 4 Bus with marked shutoff locations. (6) Standpipe to get water into passenger and engine compartments (4) Indicator shows if internal tank valves are open (3) Symbol on panel shows location of shut-off (5) Access hole in engine compartment panel for dry chemical extinguisher (1) External signal for combustible gas alarm (2) Arrow warns of PRD release point overhead FIGURE 5 Features of CNG bus to facilitate firefighting.
INCIDENT RESPONSE Possibility of PRD Release Although procedures generally call for responders to check for a gas release, the procedures do not adequately describe or illustrate the direction and extent of the gas jet or torch flame that may result from a PRD release. A video could be particularly useful for training firefighters in what to expect. Control of Ignition Sources For a fire to occur, several conditions must be met simulta- neously, including the presence of a fuelâair mixture within the flammable range and the presence of a suitable ignition source. Guidelines are needed on the distance from a CNG bus that flares and other strong ignition sources can be used. It is sus- pected that the safe distance is less than generally assumed, perhaps as little as 10 to 20 m (35 to 75 ft). More information on transit situations is needed to set reasonable procedures. Some safety instructions forbid the use of flashlights and cellular phones near a CNG bus. Cellular phones are very weak ignition sources, and a recent analysis by the Institute of Electronic and Electrical Engineers has indicated that cel- lular phones can be discounted as ignition sources for hydro- carbon vapors (4). Given the importance of cellular phones in emergency communications, additional tests that can fur- ther quantify this hazard under transit conditions would be desirable. INFORMATION MANAGEMENT Fire Department Information Notebooks Although much work and effort have gone into the preparation of information guides or notebooks for fire departments and other emergency responders, such guides could be improved. Following are several suggestions: ⢠Guides should have a quick key that matches bus num- bers with appropriate procedures. It should not be nec- essary to first look at sections for each bus fleet and then at a list of bus numbers for that bus fleet to find the appro- priate procedure. ⢠Firefighters are interested in hazard information, such as what can explode, where there are fluids, circum- stances that can lead to tank rupture, or what happens when there is a PRD release. Generally, this type of information is not available. ⢠Although many guides contain phone numbers of vari- ous transit personnel, more specific types of informa- tion could be supplied by those transit experts, if they were contacted. 38 ⢠The information in the notebooks should coordinate with information in the U.S. Department of Transporta- tionâs 2004 Emergency Response Guidebook (5). That document is frequently used by responders when devel- oping a response to a hazardous material. Fire Training Academies Firefighters are often trained at a state or regional fire academy. Working with the instructors at those academies could be a fruitful (and necessary) way to communicate transit response procedures. Firefighters may not consider transit staff alone to be a credible source of information on fire safety and emer- gency response. In this respect, it may be better to prepare responder guides jointly with someone having a fire depart- ment or fire academy affiliation. National Standard for Emergency Responders There is a perceived need for a national standard for emer- gency procedures to use in responding to natural gas bus inci- dents, to distribute to fire responders. The rationale is that the national standard would then flow down to all fire jurisdic- tions in a service area. The presumption is that with a national standard, the firefighter response to transit bus fires would be more consistent with a transit agencyâs expectations. However, it is not clear what such a standard would con- tain. Information on transit equipment tends to be specific to the transit agency involved, and it changes as new equipment is acquired and old equipment is retired. Moreover, the strat- egy used by firefighters when they arrive on the scene of a bus fire depends greatly on the response time (which affects the extent of the fire), the resources available (e.g., size of the crew and the number of pieces of fire apparatus available on the scene), the local situation (e.g., distance to an adequate water supply or distance to nearby structures), and the per- sonal preferences of the fire commander. Thus, the content of such a standard might be too general for specific application. KNOWLEDGE GAPS This study identified numerous areas where additional infor- mation and resources could benefit the transit community. Many of these areas are interrelated and are discussed here. Transit Experience with Natural Gas Buses Incident Reporting Standardized reporting of incidents involving natural gas buses and facilities would be valuable in defining problem areas and involving resources.
39 Procedures Development Overall, the survey found that more than 50% of the respond- ing transit agencies have not prepared emergency procedures for the both facility and vehicle emergencies, and 40% have not communicated any emergency procedures to local fire or police departments. Fire Department Issues Much more attention should be given to surveying fire departments and firefighters about their concerns and their experiences. Fire Department Involvement Fire department involvement in the preparation of emergency procedures was found to be minimal or nonexistent. To gain the insights and experiences of firefighters and to increase the credibility of procedures and recommendations with emer- gency responders, there is a strong need for fire department involvement in the procedure development process. Information Transfer A fire department briefing package should be developed. Before such development, fire departments should be approached to determine (1) their concerns, (2) their experi- ences with natural gas vehicles and facilities, and (3) the for- mat that they find most effective. Vehicle Fires In regard to vehicle fires, more information is needed to pre- pare a decision tree to help fire fighters determine whether or not a natural gas bus fire can be safely extinguished and the most effective strategy to use. Clearly, such a resource must be prepared jointly by the transit community and fire depart- ment experts. Debriefings There is a strong need for debriefings from firefighters who have responded to incidents involving natural gas buses fires. For firefighters, as for many professionals, the experiences of colleagues are often the most credible sources of informa- tion. Collecting this information and distilling it into lessons learned is important. Training Presentation Information resources for firefighters could include the pro- duction of a training video or slide presentation showing what to expect, what can happen, and what techniques work. Such a presentation would not show such sales-oriented top- ics as the advantages of alternative fuels, why natural gas is good for the environment, or how safe natural gas is com- pared with gasoline. It would show fire department responses to actual natural gas bus emergencies and would focus on specific emergency response techniques, potential hazards to firefighters, and methods of fire attack that minimize damage to the bus. Technical Information Ignition Sources Some statements and procedures for avoiding possible igni- tion sources, though well intentioned, appear to lack a techni- cal foundation of experimental measurements or detailed calculations. For example, as mentioned, recent statements by the IEEE have cast doubt on the need to consider cellular phones to be ignition sources (4). Moreover, there is anecdo- tal evidence that the extent of the flammable zone associated with a natural gas release is sometimes greatly overestimated by emergency responders. However, without actual measure- ments it is difficult to suggest a different approach. Hazards from Small Gas Leaks and Releases Small leaks are often associated with fittings that are improp- erly tightened, insufficient use of pipe thread sealant, defec- tive O-rings, or foreign matter on mating surfaces. Although small leaks present only a minor fire hazard, they result in an odor of gas and can trigger methane detection systems; both are situations that can generate an emergency response. More information is needed to determine the degree to which small leaks can support a flame under practical conditions of ven- tilation and gas dispersion. Procedures for Nonodorized Gas Some transit agencies use nonodorized natural gas. LNG cannot be odorized because the odorant is a solid at cryo- genic temperatures, and CNG derived from LNG will not be odorized unless it is added by the transit agency. The use of nonodorized fuels requires a particular awareness of the need to depend on instruments for sensing the existence and extent of any natural gas releases. Bus and Facility Design Standard signage should be developed for transit buses and facilities that shows the locations of shutoffs and vents, the status of combustible gas detectors, and extinguishing points.
