Self-rescue in quantitative risk analysis

Transcription

1 Slf-rscu n quanav rsk analyss I.J.M. Trjssnaar- Buhr & I.M.E. Rabn & T. Wrsma & S.I. Wjnan TNO, Apldoorn, Th Nhrlands ABSTRACT: In quanav rsk analyss (QRA) mhods, h damag of oxc and fr ffcs o prsons s drmnd usng a fxd xposur m. Th modl dscrbd n hs papr nabls o nclud slf rscu n QRA mhods. Th modl can b usd 1) for calculaons of a mor ralsc xposur m, 2) o drmn h numbr of prsons ncapabl of slf-rscu, whch s mporan nformaon for h rscu srvcs 3) o drmn h ffc of safy masurs mprovng slf-rscu. Th modl provds a soluon bwn vacuaon modllng, whch mgh b oo m-consumng and sa-of-h-ar QRA-calculaons, whch hav nsuffcn dal o show h ffc of safy masurs. 1 INTRODUCTION If safy masurs for slf-rscu can no b assssd whn a quanav rsk analyss (QRA), h rsk judgmn sysm dos no mova compans or local auhors o ak masurs, bcaus hr ffcs ar no vsbl n a sa-of-h-ar rsk assssmn. In mos quanav rsk analyss mhods, prsons prsn n h hazardous ara ar assumd o b xposd for a fxd amoun of m. Assumpons for fxd xposur ms ar 3 mnus for a oxc xposur and 2 sconds for xposur o ha radaon. Furhrmor, prsons ar assumd o say on h sam plac. Th raly s dffrn: n cas of an mrgncy, vry prson capabl of scap wll ry o rscu hmslf. In cas of a oxc rlas s possbl ha a saf plac (for xampl nsd a buldng) s rachd whn h prscrbd 3 mnus. On h ohr hand, n cas of fr n crowdd placs, can b xpcd ha popl ar unabl o scap whn 2 sconds. Exampls of mhods ar h Duch probablsc QRA mhods for ranspor of dangrous goods and for saonary nsallaons (Uj d Haag 26). In QRA calculaons whr slf-rscu s vry mporan, for nsanc n unnl safy suds, xnsv calculaons wh vacuaon modls ar prformd. Subsqunly h oupu of h vacuaon modls s usd n h QRA, h vacuaon modl s no ngrad whn h QRA. Th modl dscrbd n hs arcl provds a soluon bwn vacuaon modllng, whch mgh b oo m-consumng and sa-of-h-ar QRAcalculaons, whch hav nsuffcn dal o show h ffc of safy masurs. Th modl can b ngrad n a quanav rsk analyss mhod, hrwh nablng o accoun for slf-rscu and o show h ffc of safy masurs by runnng a sngl QRA modl. Th modl s spcally suabl for QRA s nvolvng rsks o dnsly populad aras, such as ralway saons, sadums, and offcs as wll as for ndusral plans and hr nhabd surroundngs. 2 MODEL OUTLINE In ordr o judg h ffc of slf-rscu mprovng masurs, a modl has bn dvlopd o quanfy h ffc of slf-rscu, dpndng on xposur o fr or oxc chmcals. Th modl dsngushs ha radaon, smok and svral yps of oxc chmcals and quanfs hr ffc on h walkng vlocy and xposur duraon (s Fgur 1). Fgur 1. Slf-rscu n quanav rsk analyss

2 Ohr facors ha ar consdrd n h modl ar h dsanc o a saf locaon and h prsnc of a bolnck n h vacuaon rou. Th modl can b usd for h followng purposs: For fas calculaons of h xposur m and h numbr of prsons ncapabl of slf-rscu; To drmn h ffc of safy masurs mprovng slf-rscu, by calculang h rmanng consquncs for a scnaro afr akng masurs. Subsqunly hs consquncs can b compard o hos of h orgnal scnaro n h QRA. Th followng scons show h rlaons for dscrpon of h oxc ffcs and hr nflunc on h mobly or walkng vlocy. No ha n cas of fr, for nsanc, hr can b nracon bwn oxc xposur and ha xposur: f h mobly dcrass du o oxc xposur (smok), h xposur m o ha can ncras. 3 TOXIC INJURIES For oxc njurs a dsncon s mad bwn asphyxan and rran gass. For an asphyxan produc, such as carbon monoxd, h mos mporan crron for s oxc ffcs s h concnraon n h blood supply o h brans. On h ohr hand, for an rran produc h mos mporan facor s h concnraon n h lnng of h nos, hroa, or lung (Pursr 22). 3.1 Asphyxan fr producs Th Fraconal Incapacaon Dos (FID) modl of Pursr (Pursr 22) has bn slcd o dscrb h ffcs of asphyxan fr producs for hr prsnc n fr smok as wll as for h pur subsanc. Th FID modl rlas h oxc dos nhald by a prson o h dos whr ncapacaon (.. loss of conscousnss) occurs. Th FIN s h sum of h FID valus for all asphyxan fr producs, whch also accouns for hyprvnlaon rsulng from xposur o carbon doxd. Incapacaon occurs by a (cumulad) xposur o carbon monoxd, hydrocyanc acd and oxygn dfcncy (FIN oal =1) or by xposur o hgh concnraons of carbon doxd (FIDCO 2 =1). oal ( FID + FID ) * VCO FID ) FIN = + (1) ( CO HCN 2 O2 whr FID CO, FID HCN and FID O2 = Fraconal Incapacaon Dos for CO, HCN and O 2 rspcvly; CO = carbon monoxd; HCN = hydrocyanc acd; O 2 =oxygn; CO 2 = carbon doxd; VCO 2 = mulplcaon facor hyprvnlaon [-]. Th Fraconal Incapacaon Dos s dscrbd for CO, HCN, O 2, and CO 2 by quaon 2 o 6 (Pursr 22). 5 = [ CO] 1. RMV (2) PID FID CO 36 whr [CO] = CO concnraon n ppm; RMV =Rspraory Mnu Volum n lr/mn, whch s 25 lr/mn a lgh acvy; = xposur m n mn; PID = Prsonal Incapacaon Dos =3%. Th FIDs for oxygn and hydrocyanc acd ar dscrbd by quaons 3 and 4. Equaon 3 and 4 ar vald for rlavly shor xposur m (shorr han 1 hour) and a consan concnraon. FID = (3) O *(2.9 V % O2 ) whr V%O 2 = O 2 volum prcnag; FID HCN = (4) *[ HCN ] whr [HCN] = HCN concnraon n ppm. Carbon doxd (CO 2 ) ncrass h Rspraory Mnu Volum, rsulng n a largr upak ra of ohr gass. Th ncras of Rspraory Mnu Volum by hyprvnlaon s dscrbd by a mulplcaon facor VCO 2 :.193* V % CO VCO 2 = (5) 7.1 whr V%CO 2 = CO 2 volum prcnag. Bsds s ffc on h Rspraory Mnu Volum, CO 2 n slf can lad o ncapacaon whn prsn n hghr concnraons. FID CO = (6) 6 CO * V % Usng quaons 1 o 6, h FIN can b drmnd for oxc fr producs whn fr smok as wll as for h spara oxc subsancs. For asphyxan fr producs h m o ncapacaon and s svry usually show a shor prod of noxcaon ha s followd by a rlavly sharp dcln no ncapacaon (Pursr 22). Th rlaon bwn FIN and mobly s shown n fgur 2 (Unvrsy of Grnwch, 24).

3 Mobly facor 1,,8,6,4,2,,2,4,6,8 1 FIN or FIC Fgur 2. Mobly as a funcon of FIN and FIC 3.2 Irran fr producs FIN FIC Dos calculaons ar appld for ncapacaon ffcs of asphyxan fr producs as wll as for h lhal ffcs of rran fr producs. Howvr, h ncapacaon ffc of rran fr producs s rlad o h concnraon nsad of h dos. Th oxc ffcs ar dscrbd by h Fraconal Irran Concnraon (FIC) modl. [ HCl] [ HBr] [ HF] [ SO2 ] [ NO2 ] FIC = (7) F F F F F HCl HBr whr [HCl] = Hydrochlorc acd concnraon n ppm; F HCl = hrshold concnraon for HCl n ppm; Th hrshold valus for rran fr producs ar gvn n abl 1. Incapacaon occurs whn h FIC quals uny, for whch h oxc ffc of dffrn rran fr producs can b addd. Th rlaon bwn FIC and mobly s shown n fgur 2 (Unvrsy of Grnwch, 24). Tabl 1. Thrshold valus for rran fr producs Toxc gas Svrly rran concnraon (ppm) HBr 2 HCl 2 HF 12 NO2 8 SO2 3 HF SO 2 NO Toxc chmcals In ordr o b abl o ransla h prsnc of oxc chmcals no mobly, h mhods of FID and FIC ar also appld for rlass of oxc chmcals. Th gnral quaons for h FID and FIC mhods ar: FID = FIC = C D ( ) n n = = 1 = ( C) = 1 ( C) n = 1 C F (8) (9) whr C = avrag concnraon n ppm of chmcal ovr h chosn m ncrmn; = chosn m ncrmn n mn; D () = dos of chmcal a m ; (C) = h hrshold dos n ppm*mn; F = hrshold concnraon for chmcal n ppm. Bcaus h FID and FIC hrshold valus ar only known for fr producs, ohr hrshold valus ar rqurd for h oxc chmcals. Th Acu Exposur Gudln Lvl 2 (AEGL-2) s vry suabl for h dfnon of ably of slf-rscu. AEGL-2 s h arborn concnraon of a subsanc abov whch s prdcd ha h gnral populaon, ncludng suscpbl ndvduals, could xprnc rrvrsbl or ohr srous, long-lasng advrs halh ffcs or an mpard ably o scap. AEGL-2 valus ar avalabl for xposur duraons of 1 mnus, 3 mnus and 1 hour, 4 hours and 8 hours. Th subdvson of svral chmcals n asphyxan and rran as wll as hr hrshold valus ar shown n abl 2. Th chmcals n abl 2 ar rprsnav for varous hazard cagors as usd n QRAs. Th AEGL-2 s no (y) drmnd for acrylonrl and hylchlord, h Immdaly Dangrous o Lf and Halh (IDLH) valu s usd for hs chmcals. IDLH s dfnd as a concnraon ha an xposur up o 3 mnus dos no caus dah, srous or rrvrsbl halh ffcs, or dos no mpar or mpd h ably o scap. Tabl 2. Subdvson and AEGL-2 hrshold valus of oxc chmcals. Chmcal Subdvson Concnraon (ppm) 1 mn 3 mn xposur xposur Acrylonrl FID - 85* Ehyl chlord FID - 38* Ammona FIC Chlorn FIC Mhylsocyana FID.4.13 Nrc acd FIC 43 3 * IDLH hrshold valu Th FID can now b drmnd by calculang h hrshold dos (C) from abl 2 and nsrng hs valu no quaon 8. For nsanc, h hrshold

4 dos (C) for acrylonrl s 255 ppm*mn. Th FIC can b drmnd by akng h hrshold concnraon from abl 2, for nrc acd h valu dpnds slghly on h mscal of h calculaons (1 mn or 3 mn valu). Th FID and FIC ar ranslad no a walkng vlocy usng h rlaons shown n fgur 2. 4 THERMAL INJURIES Exposur o hrmal radaon s assumd o hav ll or no ffc on h mobly of h vcms, unl h njurs bcom lhal. Durng h slf-rscu prod, h ha radaon o whch h prson s xposd wll dcras wh h dsanc. Ths s accound for by calculang h ffcv xposur duraon (CPR 16E 1992): 5 3 x 3 u + + ff r 1 1 v (1) 5 u x whr ff = ffcv xposur m (s); x = h nal dsanc o h fr sourc (m); u = h vacuaon vlocy (m/s); r = racon m (= 5 s); v = (x s - x )/u = vacuaon m (s); x s = dsanc from fr sourc whr ha radaon s blow 1 kw/m 2 (m). Th vacuaon vlocy, u, can b nfluncd by xposur o oxc fr producs: f h mobly dcrass h xposur m o ha s ncrasd: u = mobly facor * u, whr u = maxmum vacuaon vlocy. Th ffcv xposur m oband wh quaon 1 can subsqunly b usd o calcula dgr of njurs and lhal vcms du o ha xposur. 5 EVACUATION Two mporan characrscs of h vacuaon rou ar ncludd n h modl, namly h dsanc o a saf locaon and h prsnc of bolncks on h vacuaon rou. 5.1 Dsanc o saf locaon Th dsanc o a saf locaon can b dfnd by a hrshold valu (concnraon, maxmum dos or ha radaon lvl) or can b h dsanc o a plac o shlr, such as a buldng, whr wndows and doors can b closd. Th mobly of a prson s nfluncd by h concnraon or oxc dos o whch h s xposd on hs way o h saf locaon. In cas of fr, h dsanc o a ha rssan shlr or h dsanc o 1 kw/m 2 (x s ) s nsrd n quaon Bolncks on h vacuaon rou Th vacuaon calculaons whn h modl ar no nndd o modl h vacuaon rou n dal. Howvr n cass of mporan bolncks n h rou, such as a door or sars, can b vry mporan o b abl o modl h ffc of h bolnck. Th vacuang prsons nd o pass h bolnck bfor rachng a saf locaon. Th acual xposur m ncrass du o h m ncssary o pass h bolnck. An avrag valu for h xra xposur m du o h bolnck s gvn by: bolnck = n/ C bolnck (11) whr n = numbr of prsons ha nd o pass hrough h bolnck (-); C bolnck = bolnck capacy n numbr of prsons pr mnu. 6 IMPLEMENTATION AND APPLICATION 6.1 Modl mplmnaon Th modl can b mplmnd n svral ways, hs chapr dscrbs h followng xampls: 1 Sraghforward mplmnaon for QRA mhod; 2 Dynamc mplmnaon for scnaro analyss or mor xnsv QRA calculaons. Th dffrnc n mplmnaon s h lvl of dal of modllng h ffc of oxc xposur o h vacuaon vlocy. 6.2 Sraghforward mplmnaon mhod For h QRA mhod a sraghforward mplmnaon s ofn suffcn. In hs cas h vacuaon vlocy s basd on h concnraon profl on h sarng locaon of h prson. For asphyxan chmcals, h frs sp s o sma h xposur m wh h maxmum vacuaon vlocy, u=u, accordng o: xp = r + bolnck +(x s -x )/u; (12) Subsqunly h dos s drmnd usng h concnraon profls C (x, ) on h sarng locaon of h prson: D ( ) = C ( x, d (13) ) FID and corrspondng mobly facor ar calculad wh h quaons n scons 3.1 or 3.3 and fgur 2. Subsqunly h ffcv xposur m s drmnd wh quaon 12, hs m wh u= mobly facor*u :

5 ff = r + bolnck + (x s -x ) / (mobly facor*u ) In h fnal sp h ffcv FID s drmnd usng h ffcv xposur m. Th ffcv FID s usd o drmn whhr a prson wh a cran sarng locaon wll bcom ncapabl of slfrscu durng hs amp o scap (usng fgur 2). For rran chmcals h FIC a h sarng poson s drmnd wh h quaons n scons 3.2 or 3.3 and h mobly facor s rad from fgur 2. Th ffcv xposur m can hn b calculad wh quaon 12, assumng u= mobly facor*u. Th ffcv xposur m s mporan npu for calculang lhal damag. 6.3 Dynamc mplmnaon mhod For a scnaro analyss h vacuaon vlocy wll b calculad dynamcally: whn a prson movs o anohr (safr) locaon, h wll b xposd o a lowr concnraon. Thrfor h oxc dos wll ncras lss compard o sayng on h sam locaon. For ach m ncrmn, h FID or FIC and mobly facor ar calculad and usd as npu for h nx m ncrmn unl a prson hr rachd a saf locaon or s ncapabl of slf-rscu. For rran chmcals C (x,) s npu for quaon 9. For asphyxan chmcals h dos s calculad wh: D ( ) = C ( x, ) d (13) For boh rran and asphyxan chmcals: x = x for r x = x + u(- r ) for > r u= mobly facor*u s drmnd for ach m ncrmn wh FID (as a funcon of D ()) or wh FIC and corrspondng mobly facors. 6.4 Modl applcaons Whn applyng h modl, a mor ralsc xposur m and hrwh a mor ralsc smaon of h (lhal) damag of hs xposur can b calculad. Evn mor mporan, s h us of h modl o sma h numbr of prsons n h hazardous ara, who ar no capabl of slf-rscu. Th FID and FIC can b drmnd for vry xposd prson dpndng on hs sarng locaon. If h FID or FIC of a prson xcds uny, ha prson wll b ncapabl of slf-rscu. Combnng hs nformaon on slf-rscu wh populaon daa ylds h oal numbr of prsons ncapabl of slf-rscu. Th numbr of prsons ncapabl of slf-rscu s mporan nformaon for prparaon and ral-m acvs of rscu srvcs. In ordr o drmn h rscu capacy ncssary o handl h accdn, h numbr of prsons ncapabl of slf-rscu s mor rlvan han h numbr of faal njurs. Th ffcs of safy masurs mprovng slfrscu can b drmnd wh h us of h modl. An xampl of a safy masur s ncrasng h capacy of a bolnck n h vacuaon rou or placng a shlr or saf havn. 7 CONCLUSIONS Wh sa-of h ar QRA mhods, safy masurs for slf-rscu canno y b assssd. Th modl dscrbd n hs papr nabls o nclud slf-rscu n QRA mhods. Th modl dsngushs ha radaon, smok and svral yps of oxc chmcals and quanfs hr ffc on h walkng vlocy and xposur duraon. Evacuaon rou characrscs consdrd n h modl ar h dsanc o a saf locaon and h prsnc of a bolnck n h vacuaon rou. Th modl can b usd o drmn h numbr of prsons ncapabl of slf-rscu, whch s mporan nformaon for h rscu srvcs. Furhrmor h mor ralsc xposur ms oband wh h modl can b usd for mprovng h smaon of lhal damag. Th modl can b ngrad whn a quanav rsk analyss mhod o drcly show h ffc of slf-rscu mprovng masurs. Th modl s spcally suabl for QRAs nvolvng rsks o dnsly populad locaons, such as ralway saons, sadums, offcs as wll as ndusral plans and hr nhabd surroundngs. NOMENCLATURE [CO] Carbon monoxd concnraon (ppm) AEGL-2 Acu Exposur Gudln Lvl 2: arborn concnraon of a subsanc abov whch s prdcd ha h gnral populaon, ncludng suscpbl ndvduals, could xprnc rrvrsbl or ohr srous, longlasng advrs halh ffcs or an mpard ably o scap C bolnck Bolnck capacy (prsons / mn) C (x,) Concnraon profl of chmcal (ppm) F HCl Thrshold concnraon for HCl (ppm) FIC Fraconal Irran Concnraon (-) FID Fraconal Incapacaon Dos (-) FIN Sum of h FID valus for asphyxan fr producs (-) IDLH Immdaly Dangrous o Lf and Halh (IDLH) valu: concnraon ha an xposur up o 3 mnus dos no caus dah, srous or rrvrsbl halh ffcs, or dos no mpar or mpd h ably o scap

6 n Numbr of prsons ha nd o pass hrough h bolnck (-) PID Prsonal Incapacaon Dos (%) QRA Quanav Rsk Analyss RMV Rspraory Mnu Volum (lr/mn) Exposur m (mn) ff Effcv xposur m (s) r Racon m (= 5 s) v Evacuaon m (s) u Evacuaon vlocy (m/s) u Maxmum vacuaon vlocy (m/s) V%O 2 Oxygn volum prcnag (%) VCO 2 Mulplcaon facor hyprvnlaon (-) x x s Inal dsanc o h fr sourc (m) Dsanc from fr sourc whr ha radaon s blow 1 kw/m 2 (m) REFERENCES CPR 16E Mhods for h drmnaon of possbl damag o popl and objcs rsulng from rlass of hazardous marals. Frs don. Comm for h Prvnon of Dsasrs causd by dangrous subsancs. Th Hagu: drcora-gnral of Labour of h Mnsry of Socal Affars and Employmn. ISBN Pursr, P.A. 22. Toxcy assssmn of combuson producs, In: Th SFPE handbook of fr procon ngnrng. 3 rd don. Quncy, Massachuss: NFPA. ISBN Uj d Haag, P.A.M. 26. Handldng Rscobrknngn BEVI (Gudlns for quanav rsk analyss, n Duch). Unvrsy of Grnwch. 24. Buldng Exodus Manual.