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CHAPT E R 1 INTRODUCTION 1 . 1 Scope and Methodology of the Study The ch arge to the N MAB Comm ittee on F i re Safety Aspects of Pol ymeric Ma terials was set forth in presentations made by the various sponsori ng agencies. Early i n its del i be rations, however, the committee concl uded th at its origi na l ch arge req u i red some modification and ex pansion if the cruci al issues were to be ful l y examined and the needs of the sponsori ng organi zations, fil l ed . Accordingly, i t was agreed that the comm i ttee wou ld di rect its attention to the behavior of polymeric materi als i n a fi re situation with special emphasis on human·safety considerations. Excluded from consideration were fi refighting, therapy after fire-caused i nju ry , and mechanical aspects of desi gn not related to fi re safety. The scope of the committee's study incl udes : ( 1 ) a su rvey of the state of perti· nent knowledge ; (2) identification of gaps in that knowledge ; (3) identification of work in progress; (4) evaluation of ongoing work as it rel ates to the identified gaps; (5) development of conclusions; (6) formu l ation of recom mendations for action by appropriate pu bl i c and private agencies; and (7) esti mation, when appropriate, of the benefits that might accrue through i mplementation of the recommendations. Withi n th is framework, fu nctional areas were addressed as they rel ate to specific situations ; end uses were considered when fi re was a desi gn consideration and the end uses were of concern to the sponsors of the study. Attention was given to natural and synthetic poly meric mate rials pri mari l y in terms of their compos ition, structu re, processi ng, and geometry (i.e., fi l m , foam , fiber, etc. ) , but special aspects relating to their i ncorporation into an end-use com · ponent or structu re also were included. Test methods, speci fications, defin itions, and standards that deal with the foregoing were considered . Regu lations, however, were dea l t with on l y in rel ation to end uses. The products of com bustion, i ncluding smoke and tox ic su bstances, were consid ered in terms of the i r effects on hu man safety ; morbidity and morta l i ty were treated only as a function of the materials found among the products of com bus· tion. The qu estion of potenti al exposure to fi re-retardant poly mers, including skin contact, i n situations not including pyrolysis and com bustion was addressed as deemed appropriate by the committee in re lation to va rious end uses. In an effort to clarify understanding of the phenomena accom panying fi re, conside ration was given to the mechan ics of mass and energy transfer (fire dynam ics ) . The opportun ity to develop one or more scenarios to gu ide th in king was prov ided ; however, as noted above, fi refi ghti ng was not considered. To assist th ose
M I N ES AN D B U N K E R S who m ight use natura l or synthetic poly mers i n com ponents or structures, consider ation also was given to design pri nciples and criteri a . I n organizing its work, the com mittee concl uded th at its ana lysis o f the fi re safety of polymeric materials shou ld address the m aterials themselves, the fi re dynamics situation, and the large societal systems affected. Th is decision led to the development of a reporting structu re that provides for separate treatment of the tech nical-functional aspects of the pro blem and the aspects of product end use. Accord i ngl y, as the com mittee completed segments of its work, it presented its find i ngs in the fol l owi ng five disci pl inary and five end-use reports : Vol ume 1 Materials: State of the Art Volume 2 Test Methods, Specifications, and Standards Vol ume 3 Smoke and Toxicity (Combustion Tox icology of Polymers) Vol ume 4 F i re Dynamics and Scenarios Vol ume 5 Elements of Polymer F i re Safety and G u ide to the Designer Vol ume 6 Aircraft Civil and M i l itary Vol ume 7 Buildi ngs Vol ume 8 Land Transportation Vehicles Volume 9 Sh ips Vol ume 1 0 M i nes and Bun kers 1 .2 Scope and Limitations of This Report This report speci fical ly exam i nes the pol ymeric materials used in m ines and bun kers. Underground mi nes and bun kers can be conce ived of as two- or three di mension al underground structu res th at are cl osed systems dependent on forced vent i l ation. The term "m ines" is used in this report to convey the traditional m ean ing of the word - i .e., the space and operations used in recovering sol id m ineral or organ ic deposits on the su rface or u nderground. Not i ncl uded, however, is the recovery of l iquid or gaseous deposits such as oi l , natural gas, and l iq uefied s u l phur. The term " metal and non-meta l" is used to designate a l l mines that do not produce coal , an accepted practice of the U. S. mining industry. Since undergro und m i nes are more susceptible to pol y meric fire hazards than su rface m i nes, emph asis is placed on th is type. Anc i l l ary structures i ncl udi ng mi l ls and preparation plants are excl uded from con si deration in th is report. A l arge nu m be r of u nderground mi nes are coal m i nes, man-made voids carved out of combust i bl e materi a l . They usual l y contain heavy powered equi pment and methane is constantly diffused fro m the wa l l s . There typically are several ex it corridors. Egress from the greatest nu m ber is by slope, drift, or ad it; egress from m any is by a com bination of slope, drift, adit, l adder, vertical hoist, and elevato r; egress from a few is by vertical hoist alone. Underground coal m i nes genera l l y a re structu red h ori zonta l l y or on a sl ight sl ant (two d i mensions ) . Metal m i nes usua l l y d o not contain combust i ble ores or gases, but they go deeper than and contain 2
I NTRODUCT I O N much more wood than coal mi nes and make frequent use of explosives. They often are constructed in a m u lt i-l ayered fashion (three di mensions ) . Only those bun kers that are underground spaces si m i l a r to mines i n layout, con struction, usage, hu man occupancy, or i ntensity of activity are considered i n t h i s report, a n d the term "mi nes" is used in t h e text t o include both m ines and bun kers. Bun kers that are used for storage, l iving, or recreational purposes must have good access and egress routes , be compartmenta l i zed to control fire spread, and have a smoke ven til ation system. Aside from these consi derati ons, the problems of polymeric materi als usage and fire safety are analogous to those involved with other fac i l ities of simi lar function, and reference sh ou l d be made to Vol u mes 7 and 8 in th is series, B u i l di n gs, and Land Transportation Veh icles. B u n kers used for l iquid storage are outside the scope of this report, and bun kers constructed for m i l i ta ry purposes a re not discussed because of security reasons. F i re ignition sou rces in m i nes and bu n kers vary, but the most frequent a re electricity (arcing or overheating ) , weldi ng, and mechanical heat ( fricti o n ) . The special problems of l i m ited access, forced ventilation, and powerfu l ignition sou rces requ ire th at great care be exercised in the use of pol ymeric m aterials to avoid any add i tional fi re hazard because of ease of i gnition , rapid fl ame spread, and evol ution of smoke and toxic fumes. 1 .3 Bunkers - A Special Consideration A bun ker original ly was considered to be a large bin, a bi n for fuel on sh ipboard, a sand pit, or some other artificial fort ification. Today, i t is normally th ought of as an u nderground or abovegrou nd fortification to secl ude humans, ammun ition, or other suppl ies. However, underground space is used in m any other ways. Some of these u nderground instal lations are similar to m ines ( i .e., they have l i m ited access and have a soil or roc k overbu rde n ) , and, in some cases, they are actu ally located i n spaces that were formerl y m i nes. Undergrou nd space may be classi fied as to its depth from the earth 's su rface, method of formation, earth strata, or use. To rel ate to convent ional (aboveground) buildings, the fol lowi n g end-use classification is presented : 1 . Storage - One of the principal uses for u nderground space, including natu ral caves, is for storage (e.g., dry storage for goods ; refri gerated storage ; storage of records, agricu l tural products, petroleum prod ucts, gold and other pre cious metals, and munitions ) . Underground faci l ities are particularly wel l suited to col d storage and these re present about one·tenth of the nation 's capacity. Some bu rial spaces also may fit this category . 2. Trans portation - Extensive use is made of u ndergrou nd space in the form of veh icu lar tunnels, su bway stations, park ing garages, and anci l l ary fac i l ities. Some garages may be underground extensions of h igh -rise bu ildings deve l oped to conserve spaces. 3. Commerce - Underground shopping centers, i ncl uding various types of 3
M I N ES A N D B U N K E R S shops, restau rants and nightcl ubs, are fou nd i n a few scattered l ocations including Washington, D.C., Crystal City, Va., Atl anta, Ga., and the Kansas City, Mo. , a rea. 4. Manufactu ri ng - Relative l y few manufactu ring plants are found i n u nder· ground space but some examples i ncl ude a precision instru ment producer, boat manufacturer, pool table assembl er, and printer. These u ses usu a l l y are l i m i ted to those that requ i re a special environment (e.g., free from v i bration or with contro l l ed hu midity ) . 5 . Agricultural - Natural caves o r artificial ce l l a rs are widel y u sed fo r proc essing and storing wine. Mushroom farms are occasion a l l y located in aban doned l i mestone mi nes or other underground spaces . The recovery of guano from natural caves is another usage example. 6. Office Space - Offi ces are fou nd underground to a l i m ited extent where underground space is being uti l ized fo r other purposes (e.g., shopping cen ters ) . Others are constructed for defense secu rity purposes. 7. Uti l ities - Extensive use is made of underground uti l ities. In addition to extended sewage systems and the simpl e burial of pipes and ca bles, there are m u l ti-use tu nnels that contain cables and pipes. Some use is also made of underground space for sewage and wate r treatment plants. 8. I nstitutional - This incl udes schools, l i braries, m useu ms, and hospitals. These uses represent essential l y depository (storage ) facil ities and tem porary living and working quarters, laboratories, lectu re hal l s, and display centers. In most cases, these underground facil ities are extensions of high-rise bui ld ings. 9. Habitation - Lim ited use is made of u ndergrou nd space for human resi dences. These homes m ay be designed with a view i n to an open atrium and have only a few feet of soi l cover. 1 0. Defen se - Defense usage most closely fits the conventional def i n ition of a bu n ker. I ncl uded, however, are m issi l e silos, com m and and com mun ications fac i l ities, aboveground m u n ition bun kers, and air raid or bomb shelte rs . These examples are n o t intended t o be al l inclusive, b u t rather t o g ive perspec tive to the many uses of underground space. Consideration of the Kansas C ity area, where approx imately 25 mi l l ion squ are feet of undergrou nd space have been devel oped for ma ny purposes , can contri bute to identifying the scope of such develo p ment. Th is area is particu l arly suited to the devel opment of u nderground space because of extensive l i mestone m i n i n g operations, suitable geology , and a need for space that ma kes use of such space economica l l y attractive. Alth ough the number of people wo rki ng, l i vi ng, shoppi ng, or traveling u nder grou nd is relative l y small compa red to the total popu l ation, it does represent a sign ificant amount and appropri ate consideration must be given to fire safety . Exami nation of a l ist of uses presented above gives an ind ication of the wide variety of polymeric materials that wi l l be found in u nderground space. 4
I NTRODUCT I O N Although the deve lopment of underground space has been rel ativel y l i m ited i n the Un ited States, th is t ren d m a y change i n the future because o f energy considera tions a nd the lack of choice aboveground space . In many cases, the determ ination wi l l be based on econ omics. Major differences that must be ex ami ned i n consideri ng the fire safety aspects of poly meric materials in underground space as opposed to conventional bui ld ings a re the l i m itations in venti ng smoke and heat, access by firefighting equi pment, and aven ues of egress. F i re in an u nventi l ated u nderground space is an ad ia batic process si nce heat cannot escape or be removed as it is in aboveground fi res. Also, the oxygen content wi l l be depleted rapidl y and the products of com bustion therefore wi l l be different from those in an open fire . On the other hand, if forced venti l ation is i nduced i n an u ndergrou nd space fire, both of the above conditions w i l l ch ange abru ptl y and a wide array of poss i bi l i ties become feasi ble. 1 .4 Co mmittee Viewpoints Mem bers of the commi ttee are involved with materials research and devel op ment, appl ications, and system des i gn and eva l uation; l iaison representatives deal with research and devel opment, regu l ation, procurement, operations, and analysis. Thus, aspects of each material (and its problems) were su bjected to a fu l l spectru m of expertise. F u l l and extensive commun ication over the lengthy period of the com m i ttee's operation provided an unusual base for augmentation of the expertise and rounding of knowledge. Many statements about the fi re safety aspects of pol ymeric m aterials a ppear in each of the reports pu bl ished as a resu lt of the comm ittee's study. Mem be rs of the com m i ttee wish to emphas ize that such statements, i ncl uding judgmen tal ones i n regard t o fi re safety aspects o f materi als, especial ly end uses, apply o n l y t o the specific situations that pertain (e.g., su itabi l ity of a material from a fi re safety poi nt of view depends on many factors, incl udi ng ease of access, ease of occupant egress, prox i m ity of i gn ition hazard, proxim ity of other mate ri a ls, thermal fl u x and dura· tion of ignition source, ambient oxygen partial press u re, and fire and smoke detec tion and suppression systems in place). Th is l ist is not all incl usive, but only i nd ica tive of th e k i nds of concerns that must be considered in making a m aterials selec tion. Statements in this volume must not be ta ken out of context and appl ied to the use of identical materials in other situations. In addition, the ch anging nature of the problem as ti me goes on and additional experience is acquired m ust be recogn i zed by the reader as it was by the comm ittee . This viewpoi nt m ust be em phasized so that i n formation that appears in al l pu bl ished reports of th is com mittee's stu dy is not misused by tak ing it out of context. 1 .5 O rganization of This Repo rt Chapter 2 in this report summarizes the concl usions and recommendations of 5
M I N ES A N D B U N K E R S t h e committee. Olapters 3-6 are devoted t o a rev iew of t h e state o f t h e art of the subject materia l . Specifica l l y, Chapter 3 , F i re Dynamics a n d Scenarios, incl udes statistics o n m i ne disasters, ex pl a i ns devel opment of fire scenarios, and presents several such fi re scenarios. These scenarios of mine fires involving pol ymeric m aterials are i nspi red by real i n cidents and attem pt to i l lustrate the most frequent h azardous situations. These scenarios are anal yzed with attendant explanati ons of rel ated fire dynam ics. H owever, the reader is cautioned against accepting these synthesized scenari os as reports of actua l events. In Chapter 4, Materials, the potential contri bution of polymeric materials to mine and bu nker fi res is descri bed. Exami ned in deta i l are n atural and man-made m ateria ls, their application in the m i n i ng environment, and ex pected beh avior i n a fire situation. E m phasis is placed on specific danger and prevention areas . Chapter 5, Design Criteria in Mine Safety and Hazard Control, reviews present k nowl edge, explores fire and ex plosion control, and descri bes the mine env i ron ment and appl ied materials and equipment with rel ation to fi re and explosion h azard. The effect of imposed regu l ations u pon design , m aterials selecti on, and operati ng practices is then exami ned ; areas of current and proposed research th at wou ld i mprove mine fire control are del i neated. In Chapter 6, Smo ke and Tox icity, experi mental and clin ica l data are ex am ined, and the effects of temperature of com bustion on various materi als are explored. Considerations specific to mine and bun ker envi ronments are presented. I n the afterword, general an d societal considerations are d iscussed . The impl ica tions of mine d isasters to workers, mi ning econom ics, and society in general are considered . The role of legisl ation and un ion activity in mine safety also is brief l y expl ored. Appendixes present statistics on fi res in U n ited States and United K i ngdom mines ; a rev iew of the combustion products of pol ym ers and the physiologica l h azard of selected com bustion products ; a review of tox ic ity ; i n fo rm ation concern ing the eval uation of the hazard of smoke , tox ic fum es ; and measurements of smoke opacity. 6
