Fire Safety Journal, 8 (1984/85) 3 - 7 3

F i r e S a f e t y C o n c e r n s f o r Ra i l R a p i d T r a n s i t Systems

JIM BURNETT National Transportation Safety Board, Washington, DC 20594 (U.S.A.)

(Received August 2, 1983)

SUMMARY

A fire within an underground rail rapid transit system, particularly in a tunnel loca- tion, poses a highly hazardous condition to passengers, transit employees and emergency response personnel. Certain considerations in the improvement o f fire safety are universal to all transit systems.

A number o f problems have been identified by the National Transportation Safety Board, an independent U.S. government accident investigation agency, as warranting immediate attention to minimize the threats posed. The Safety Board's concern was heightened by several accidents on rail rapid transit systems involving many passengers. The fact that dur- ing peak hours, a single rail rapid transit train could carry as many as 1500 to 2000passen- gers was not overlooked. Specifically, the Safety Board reviewed the following topical areas which may complicate fire and life safety in confined rail rapid transit tunnel locations: - - t r a n s i t car materials: combustibil i ty and toxicity; - - emergency tunnel ventilation; - - t u n n e l emergency evacuation considera- tions; - - communications; - - breathing equipment; -- mobility.

I t is hoped that the lessons learned in our accident investigations involving fire and emer- gency evacuations will add to the collective knowledge o f transit systems and emergency response personnel to further minimize the hazards.

INTRODUCTION

In July 1980, the National Transportation Safety Board (Safety Board) convened a major public hearing on rail rapid transit (RRT)

safety. This hearing was prompted by a series of fires in which a number of fire safety con- cerns were raised. These safety problems war- ranted immediate consideration by the U.S. RRT industry, fire service professionals, and local, state and federal governments because the accidents posed an enormous potential for disaster. The Safety Board's alarm was heightened by the fact that during peak hours, a single R R T train could carry a "crushload" of 1500 to 2000 passengers. Under such con- ditions, the loss of life in an accident, fire, or other emergency could well be catastrophic. Because of this threat, the Safety Board brought together representatives of transit system management and labor, local fire de- partments, national fire safety organizations and state and federal agencies to explore how the fire safety record of rail rapid transit sys- tems in the United States could best be im- proved.

Fire safety is critical in R R T systems be- cause flame spread, smoke emission and toxic fumes in the limited confines of subway tun- nels can be extremely hazardous and partic- ularly difficult to control.

One noted fire official described the New York subway system as " . . . a long narrow cellar filled with thousands of people, live electrical equipment, and moving vehicles". Still another fire official termed the San Fran- cisco subway system " . . . a skyscraper without windows, lying on its side". In many respects the comparisons are accurate, yet , they are not entirely adequate to convey an under- standing of the many varied problems which complicate fire and life safety in confined RRT tunnel locations.

TRANSIT CAR MATERIALS: COMBUSTIBILITY

AND TOXICITY

One major area of conern developed through accident investigations, continuing evaluation

0379-7112/84/$3.00 © Elsevier Sequoia/Printed in The Netherlands

of R R T safe ty , and the publ ic hear ing was the i n t r o d u c t i o n in to t ransi t sys t ems o f new syn- the t ic mater ia ls which are l ightweight , a t t rac- t ive and conven i en t to use. As these mater ia l s became available, R R T sys tems used t h e m in t ransi t car seat cushions , m o l d e d par ts , wall panel ing, electr ical insula t ion and o the r car par ts because o f weight , c o m f o r t , conven ience and aesthet ics . U n f o r t u n a t e l y , thei r charac- terist ic combus t ib i l i t y , smoke-gene ra t ion and t ox i c i t y when e x p o s e d to fire were no t ful ly exp lored . As a resul t , a genera t ion of R R T cars was designed and buil t which, when ex- posed to fire, posed subs tant ia l risks to pas- sengers. These cars also were cos t ly to re t ro f i t .

The c o n t r i b u t i o n of such c o m b u s t i b l e inte- r ior mater ia ls used to the g rowt h o f a fire once it has s t a r t ed is p r o b a b l y bes t exp la ined by the p h e n o m e n o n called " f l a shove r " . The Fire Protection Handbook of the Nat iona l Fire P ro t ec t i on Associa t ion (NF P A) descr ibes the po ten t i a l c o n t r i b u t i o n o f c o m b u s t i b l e mater ia ls in an enc losed area to rapid f l ame spread:

Recent full-scale room and building fire tests have shed new light on the phenomenon called "flash- over". Previously, it was beheved that combustible gases, released during the early stages of a fire, col- lected at the ceiling level, gradually mixing with air until within the flammable range. At this point, ignition would occur, suddenly and rapidly; hence, the descriptive term flashover. It is currently held that, while this ignition of combustible gases may occur, it precedes the flashover. Flashover is now believed to be caused by thermal radiation feed- back from the ceiling and upper walls, which have been heated by the fire. This radiation feedback gradually heats the contents of the fire area. When all the combustibles in the space have become heated to their ignition temperatures, simultane- ous ignition occurs [ 1 ].

Cer ta inly , the dangers of syn the t i c mater ia l s t h a t are e x p o s e d to f ire have been shown b y several m a j o r fires in buildings in the last de- cade. Likewise , the role of syn the t i c mater ia l s as a f a c t o r in spreading fires on rail rap id t ran- sit e q u i p m e n t has clear ly been d o c u m e n t e d , as in the 1976 "Chr is t ie F i r e " on the T o r o n t o Trans i t Commiss ion (TTC) and the 1979 fire in the T ransbay Tube on the Bay Area Rap id Trans i t Dis t r ic t (BART) . In b o t h of these fires the f l ame spread and s m o k e emiss ion were so rap id t h a t r e spond ing e m e r g e n c y service per- sonnel were unab le to cope wi th the s i tuat ion. Inves t iga t ions o f these t w o acc idents led to conc lus ions t h a t seat cush ion mater ia ls - -

s ty rene bu t ad i ene on the TTC tra in and poly- u r e thane on the B A R T tra in - - were respon- sible fo r the ra te of g rowth of the fires. A Sta te of Cal i fornia Public Util i t ies Commis - sion represen ta t ive tes t i f ied at the Safe ty Board ' s hear ing tha t :

.tests [on BART cars] demonstrated that in the event that the car floor is breached by fire near a seat, there would be flames at the ceiling within 3 or 4 minutes and full involvement (flashover) would occur no more than a further 2 minutes. It would be imperative to evacuate people on the incident car and adjacent cars before flashover oc- curred. Such a fire wouls also produce enormous quantities of black, toxic smoke [ 2 ].

A l though the Sa fe ty Board has been con- ce rned wi th mater ia ls used in the in ter ior o f t rans i t cars, the re also are danger areas where- ever heavy electr ical wiring is found . Many o f the mater ia ls used to coa t electr ical wiring m a y pose t o x i c i t y hazards . Fo r example , elec- tr ical arcing b e t w e e n wires coa t ed wi th po ly- vinyl chlor ide (PVC) insula t ion can p r o d u c e subs tan t ia l and le thal quant i t i es of phosgene gas and h y d r o g e n chlor ide , accord ing to tests c o n d u c t e d b y the U.S. Na t iona l Bureau of S tandards . Since m o s t t rans i t car fires are electr ical - - pe rhaps as m a n y as 90% - - and 65% of t rans i t fires or iginate unde r the f loor o f the car, where the car ' s heavy d u t y elec- tr ical e q u i p m e n t is loca ted , par t icular a t ten- t ion m u s t be given to this area.

Cer ta in ly , the t rans i t i ndus t ry in the Uni t ed Sta tes n o w is a b u n d a n t l y aware t h a t poly- u r e t h a n e and o the r syn the t i c p r o d u c t s are subs tan t ia l risks in the event o f a fire. Indeed , the Chief Surgeon o f the Board of Police and Fire Surgeons for the Distr ic t o f C o l u m b i a tes t i f ied at the Sa fe ty Board ' s hear ing tha t :

Plastic and synthetic materials should not be used in subway car construction because of the "flash- over" potential and rapid buildup of toxic gases in a fire situation.

The B A R T fire of J a n u a r y 17, 1979 , in which burn ing p o l y u r e t h a n e seat cushions p r o d u c e d a dense, b lack s m o k e and h y d r o g e n cyan ide gas, killed a f ire f ighter . His dea th was a t t r i b u t e d to s m o k e inha la t ion and cyan ide poisoning.

His tor ica l ly , f ire dea ths due to s m o k e inha- la t ion have been a t t r i b u t e d p r imar i ly to car- bon m o n o x i d e . Recen t ly , the F o u n d a t i o n for Fire Safe ty , a n o n p r o f i t o rgan iza t ion , an- n o u n c e d t h a t i t will s t udy the role of o the r

toxic products emitted by a wide variety of synthetic, plastic and other materials. Perhaps this effort will shed further light on precisely what incapacitates and kills people in fires, particularly in subway tunnels.

EMERGENCY TUNNEL VENTILATION

It became apparent from the Safety Board's hearing that fire service officials consider emergency ventilation to be a fundamental safeguard in raft rapid transit tunnels.

Emergency ventilation systems must be capable of rapidly removing smoke and toxic gases. Unfortunately, emergency ventilation systems in some transit systems were designed prior to the introduction of new synthetic materials into transit cars. The result has been that under actual fire conditions the emergen- cy ventilation systems were unable to handle the large amounts of smoke emitted from burning synthetic materials. This has made passenger escape and tunnel access by fire fighters difficult in major transit fires.

Additionally, emergency procedures for control of air flow must be carefully pre- planned. In several fires, RRT ventilation operations were not coordinated effectively with fire service personnel and when fire fighters arrived to combat the fire, they were driven back when smoke was drawn in the wrong direction. Perhaps one way to solve such problems is to test emergency ventila- tion systems with smoke generators on a periodic basis to insure that the systems func- t ion effectively under a worse-case fire and smoke scenario.

TUNNELEVACUATIONS

As a general rule, it was found that under- ground transit systems plan to move any disabled train to the nearest station to disem- bark its passengers. Emergency evacuation of passengers on foot in a tunnel is a last resort. Recent accidents have demonstrated that conditions may make it impossible to move a train to the nearest station or transfer passen- gers to another train. Obviously, evacuations in tunnel conditions are very difficult. Transit tunnels were not being designed to provide adequate means of escape for the large number

of passengers which may be involved in a fire emergency.

The Safety Board's hearing showed that retrofit of present underground transit tun- nels would be difficult or even impossible. However, there are some corrective actions that can be taken to improve underground tunnel evacuations. For example, most transit systems are designed with a walkway along one wall of the tunnel. Tunnel evacuations may be necessary onto the walkway, rather than the track bed where the electrified third rail poses a serious safety hazard in evacua- tions. Study of walkways in transit systems reveals that pipes or other equipment often protrude from the tunnel wall, reducing the ease of access on the walkway. Engineering changes to remove such impediments could significantly improve the speed at which pas- sengers could get away from disabled trains by using walkways.

Normal lighting in transit tunnels is gen- erally adequate. Most lighting is located near the top of the tunnel. However, in the event of a fire, with moderate to heavy accumula- tions of smoke, visibility can be reduced sub- stantially. In the BART accident, for example, passengers said the smoke was so dense that they could not see the walkway and tunnel lighting was obliterated. The placement of tunnel lighting should be reviewed for maxi- mum effectiveness in emergency conditions.

Once passengers must exit transit cars in an emergency, the need for directions and signs indicating exits becomes critical. Everyone is familiar with emergency exit signs in public buildings which indicate emergency exit routes. The Safety Board determined in its hearing that all rail rapid transit systems use signs, located at intervals throughout under- ground tunnels, to give directions. These signs, called "chain markers", generally have arrows and numbers to indicate direction and dis- tance in feet to the nearest station and/or emergency exits in either direction.

Unfortunately, transit systems have no standard criteria for these chain markers. They vary from one transit system to another, and in some cases within a single system. Differ- ences include the amount of information, the way it is displayed, marker height, and dis- tance between markers. For example, some transit systems include the word "ex i t " on chain markers; some do not. Some chain

markers do not make it clear that the num- bers displayed represent the distances in feet to the nearest exits. Certainly, these types of chain markers probably are understood by persons who are familiar with them, but the Safety Board is concerned that they could be meaningless to passengers having to evacuate a tunnel on foot.

As a result of the Safety Board's study of this problem at least one transit system has reviewed the effectiveness of its chain markers and has considered new markers -- possibly " with highly reflective material for improved visibility -- that will stand out from the tun- nel wall.

Emergency Evacuation Times All transit systems have established proce-

dures for emergency evacuation. Generally, these procedures include notification of fire and emergency service organizations, shut- down and restoration of third rail power, operation of emergency ventilation systems, evacuation of passengers, on-the-scene coor- dination with emergency service personnel, and actions to be taken by transit motormen and other employees. A major concer devel- oped at the Safety Board's hearing was the time it takes to evacuate all passengers from a fully loaded transit train. It was found that this information is unavailable until a real fire or other emergency develops. Such experi- ences in the United States have shown that it takes 50 - 90 min to evacuate underground transit trains in an emergency. If fire and toxin smoke levels are contained, the evacuation times presented no difficulties. However, new transit cars emit so much toxic smoke when burning that evacuation times of 50 - 90 min may not be acceptable. Evacuation can be further delayed by failures of emergency pro- cedures. Usually, this is the result of insuffi- cient testing of the emergency procedures under simulated conditions to verify the effec- tiveness of the procedures before an actual fire incident or accident occurs. As a result of the Safety Board's concern, several transit properties have made concerted efforts to im- prove their emergency procedures and their pretraining for emergencies. This has included monitoring by observers and follow-up cri- tiques by participants and observers. Even though there is still much work to do in im- proving evacuation times in the event of an

emergency, the Safety Board has been pleased by these efforts.

OTHER EMERGENCY CONCERNS

The Safety Board has found that tunnel fires or smoke incidents also pose serious prob- lems with communications, breathing appara- tus and the mobility of fire and rescue forces.

Communications In a tunnel, emergency fire and rescue ef-

forts cannot be effective without extensive communications among fire, rescue and tran- sit system personnel. Conventional communi- cations normally used by fire service organi- zations often are ineffective in tunnels with- out special equipment.

At the Safety Board's hearing, fire service officials said it was essential that underground tunnels be equipped with dedicated emergency communications systems and a telephone sys- tem or capability for use of portable tele- phones. Inadequate communications has been identified as a serious problem in many of the fires that have occurred on rail rapid transit systems. Because of this, many transit systems have acted to upgrade existing communica- tions or to retrofit with new equipment. The Administrator of the United States Fire Ad- ministration testified that " . . . t h e English and Germans are experimenting ... at the present time with some novel approaches", to emer- gency communications for transit systems. I am confident that any such technological innovations will be shared worldwide.

Breathing Equipment Generally, the usefulness of fire fighters'

breathing apparatus is of short duration. This equipment may not provide adequate breath- ing capability for the extended periods of time that can be involved in rescue operations and fighting of underground transit fires. Most fire department breathing equipment has a nominal 30-rain rating, but fire fighters in tunnel emergencies may have to travel a mile or more in heavy toxic smoke conditions. Considerable at tention thus should be given to insure that long-term (one-hour or more) breathing equipment is available, and that it is reliable, safe and easily maintainable.

Mobility One final area where improvements can be

made is the use of specialized equipment to transport fire response personnel and their equipment to a fire. Generally, fire fighters can transport themselves and their equipment to tunnel access points, such as stations and vent openings. However, once at these loca- tions their equipment must be off-loaded and hand~arried. If the fire is not at a location easily accessible by foot , fire fighters can be forced to spend precious time and energy simply getting to the fire.

Sometimes transit trains can be used to transport fire fighters and equipment, but these trains depend on third rail electrical power. Third rail power often is shut down quickly. In addition to the delay this can cause for fire fighters, passenger evacuation and rescue of trapped and injured passengers also can be complicated.

CONCLUSION

I believe that the findings of the Safety Board's hearing into railroad transit fire safety

as a result of accidents and incidents in the United States, highlight concerns that are common to all such systems worldwide. The lessons learned from these accidents and inci- dents need to be shared. Many improvements can be made in the planning, design, construc- tion, and operation of underground transit systems to minimize the "learning curve" in an actual fire emergency. I urge those persons with public responsibility for rail rapid transit safety to review the fire safety of their sys- tems -- promptly and carefully.

REFERENCES

1 G. P. McKinnon (ed.) and K. Tower (ass. ed.), Fire Protection Handbook, NFPA, Boston, MA, 14th edn., January, 1976, Section 6, p. 89.

2 Safety Effectiveness Evaluation of Rail Rapid Transit Safety, National Transportation Safety Board, Washington, DC, January 22, 1981, p. 18.