Toxic Hazard and Fire Science - ACS Symposium Series (ACS

Chapter 6

Toxic Hazard and Fire Science

Downloaded by KTH ROYAL INST OF TECHNOLOGY on December 7, 2015 | http://pubs.acs.org Publication Date: May 9, 1990 | doi: 10.1021/bk-1990-0425.ch006

Howard W. Emmons Division of Applied Sciences, Harvard University, Cambridge, MA 02138

The manner in which toxicological knowledge must work together with the knowledge of human behavior, fire dynamics, and chemistry to produce an acceptable level of fire safety is proposed. A hypothetical example illustrates what must be done with adequate accuracy in order to design fire safety to a performance code. The example may give the impression that this can already be done. In fact, each computer code used contains dozens of assumptions, some very crude, so that the accuracy of present predictions are unacceptably low. The u l t i m a t e o b j e c t i v e of the study of t o x i c i t y of f i r e - p r o d u c e d t o x i c agents i s the design and c o n s t r u c t i o n of a f i r e - s a f e environment. There are many ways t o accomplish t h i s aim. We might develop m a t e r i a l s which, when heated, produce no t o x i c gases. We might use m a t e r i a l s which do not burn. These f a n c i f u l s o l u t i o n s t o the f i r e problems of s o c i e t y a r e already p o s s i b l e . We c o u l d make everything from s t e e l , r e i n f o r c e d concrete, and ceramics, a s o l u t i o n that i s uncomfortable, unesthetic, and unacceptable. We thus commit ourselves t o a balancing of r i s k , c o s t , and d e s i r a b i l i t y . We would l i k e our b u i l t environment t o s a t i s f y a performance code which s t a t e s t h a t " a l l occupants of t h i s b u i l d i n g w i l l be able t o s a f e l y e x i t o r reach a safe refuge area no matter where o r when a f i r e s t a r t s . " This performance code may seem e q u a l l y f a n c i f u l . I t i s t h e purpose of t h i s paper t o d i s c u s s what i s necessary t o reach that goal and t o show the progress t o date. We can see what i s necessary by l o o k i n g at more mature engineering f i e l d s t o see how s a f e t y i s assured. B u i l d i n g s t r u c t u r a l design, f o r example, s a t i s f i e s a performance code which avoids b u i l d i n g c o l l a p s e by r e q u i r i n g the safe support of s p e c i f i e d f l o o r loads f o r various purpose rooms. The s t r u c t u r a l engineer s e l e c t s an appropriate d e t a i l e d design by use o f s c i e n t i f i c a l l y d e r i v e d and c a r e f u l l y v a l i d a t e d formulas. F i r e s a f e t y design requires the same kind of approach. We must develop the necessary s c i e n t i f i c q u a n t i t a t i v e understanding of f i r e so as to be able t o p r e d i c t the l e v e l of a b u i l d i n g ' s f i r e s a f e t y . Again, l o o k i n g a t s t r u c t u r a l engineering, we see the use o f simple formulas f o r beams, columns, j o i n t s , r e e n f o r c i n g rods, e t c . , which permit q u a n t i t a t i v e e v a l u a t i o n of s t r u c t u r a l s a f e t y . The phenomena of f i r e a l s o r e s u l t s i n

0O97-6156/90/0425-O067$06.00/0 © 1990 American Chemical Society

In Fire and Polymers; Nelson, G.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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formulas—sometimes not so s i m p l e — b y which f i r e s i g n i t e , grow, decay, and e x t i n g u i s h . However, i n the f i r e case, the i n t e r a c t i o n s of p h y s i c a l , chemical, p s y c h o l o g i c a l , and p h y s i o l o g i c a l e f f e c t s are so complex and numerous t h a t , u n t i l the advent of the modern computer, comprehensive q u a n t i t a t i v e p r e d i c t i o n s of f i r e s a f e t y were f a r beyond our computing capacity. What needs t o be p r e d i c t e d to assure f i r e s a f e t y ? Occupants must be a l e r t e d t o the e x i s t e n c e of a f i r e i n t h e i r b u i l d i n g . We must be able to p r e d i c t what they w i l l do; v e r i f y the alarm, t r y to f i n d and e x t i n g u i s h the f i r e , n o t i f y others of danger, help handicapped, and move along an escape route. As they delay t h e i r escape more, the f i r e continues t o grow. Thus, by the time that they walk, run, crawl along the escape route, there may be hot, t o x i c gas along the way. I f the exposure i s too high, they may be i n c a p a c i t a t e d and perhaps l a t e r , d i e . To p r e d i c t a safe escape from a b u i l d i n g , we must know where the occupants may be, p r e d i c t t h e i r behavior, p r e d i c t t h e i r exposure t o hot, t o x i c gases, and p r e d i c t the e f f e c t of these gases. Before any of these p r e d i c t i o n s are p o s s i b l e , we need t o p r e d i c t the f i r e . The f i r e l o c a t i o n , i g n i t i o n , and growth c o n t r o l s the time at which the i n s t a l l e d alarm system detects and announces an emergency. The f i r e and the d e t a i l s of the b u i l d i n g design c o n t r o l s the time h i s t o r y of the gas temperature and composition on the escape route and these d e t a i l s must be p r e d i c t e d by s c i e n t i f i c a l l y - b a s e d f i r e s a f e t y engineering. With t h i s information, i t w i l l be p o s s i b l e t o p r e d i c t the time of the alarm and the hazards on various escape routes. I t w i l l then be p o s s i b l e t o p r e d i c t whether or not a l l b u i l d i n g occupants can s a f e l y escape. T h i s f i r e s a f e t y engineering program may sound as f a n c i f u l as some of my f i r s t suggestions. I t was considered impossible 30 years ago. In f a c t , 30 years ago, i t was impossible. But i n 1989, i t i s not only p o s s i b l e , but a l l p a r t s of the r e q u i r e d science are making s i g n i f i c a n t progress toward the minimum necessary l e v e l , and present computer codes can p r e d i c t many, but by no means a l l , of the e s s e n t i a l p a r t s of t h i s program ( a l b e i t at unacceptably low accuracy). I l l u s t r a t i v e Example To make c l e a r how f a r we have come along t h i s road, l e t us compute a s p e c i f i c f i r e . Consider an apartment house with v a r i o u s apartments opening onto a 44m (144.4 f t ) long c o r r i d o r , Figure 1. A f i r e occurs i n a 4 x 5 x 2.4m (13x16x8 f t ) room 30 meters (98.4 f t ) from the open end of the c o r r i d o r . A family, father, mother, young boy, and baby, are asleep i n a s u i t e of rooms at the c l o s e d end of the c o r r i d o r . The room where the f i r e occurs c o n t a i n s a bed, polyurethane mattress, an upholstered p o l y s t y r e n e frame, polyurethane foam padding and f a b r i c c h a i r and a wooden d r e s s e r . The f i r e s t a r t s i n the upholstered c h a i r . The door t o the f i r e room i s c l o s e d u n t i l the p h o t o e l e c t r i c d e t e c t o r i n the room alarms and the occupant a f t e r ten seconds leaves the room and leaves the door open. The occupants i n the d i s t a n t s u i t e , a f t e r v a r i o u s delays, move down the c o r r i d o r t o escape. At present, there i s no one computer f i r e code s u f f i c i e n t l y comprehensive t o compute t h i s f i r e , i n c l u d i n g the people's response. In f a c t , no combination of present codes can s o l v e t h i s problem with the r e q u i r e d engineering accuracy. To get an approximate i l l u s t r a t i v e s o l u t i o n t o t h i s case, a number of d i f f e r e n t computer f i r e codes must be used i n succession and hand f i t data t r a n s f e r r e d from one to the next. The computer programs used t o make t h i s (low accuracy) p r e d i c t i o n and some of t h e i r o f t e n severe l i m i t a t i o n s w i l l be i n d i c a t e d . The f i r e i n the c h a i r grows p r o p o r t i o n a l t o the heat feedback from a l l sources, which change with time. The flames and hot gases r i s e t o the



T

i . #3

-•I 4 4r

Fire Room

»4

K

Boy

Mm

Mother ^ Father Baby

7TT

Figure 1. P l a n o f apartment b u i l d i n g f o r t h i s i l l u s t r a t i v e fire a n a l y s i s showing four-room simulated c o r r i d o r numbers 1, 2, 3, 4; t h e f i r e room #5; and the f a m i l y s u i t e , whose f i r e s a f e t y i s t o be predicted.

55r

-3om

*2

_ Exii Ooor lo Corridor

Family Suite


13m

25 m

~7T


70

FIRE AND POLYMERS

ceiling. A p h o t o e l e c t r i c detector at the c e i l i n g alarms. The f i r e room occupant awakes, runs out of the room and leaves the door open. The flames from the c h a i r , the hot l a y e r of gas and the g r a d u a l l y h e a t i n g c e i l i n g , a l l r a d i a t e t o the bed and dresser. These items heat up and at t h e i r i g n i t i o n temperature s t a r t t o burn. As they burn, r a d i a t i o n from t h e i r flames enhance the burning rate of a l l burning objects and t h e i r plumes add t o the hot c e i l i n g l a y e r . Since the door has been l e f t open, hot c e i l i n g l a y e r gas, as soon as i t i s deep enough, flows out at the top of the door and c o l d a i r flows i n at the bottom. Soon the rate of p y r o l y s i s i n the room i s so high that a l l flammable p y r o l y s i s gases cannot burn i n the room; the room f i r e becomes oxygen starved. A l l of these phenomena were computed using the computer f i r e code FIRST. (1) (The computation took about ten minutes f o r 2,000 seconds of f i r e time on a VAX 8600.) There i s , as yet, no code which w i l l compute when the c e i l i n g l a y e r with excess p y r o l y z a t e w i l l i g n i t e and burn, nor the time when flames w i l l come out of the door i n t o the c o r r i d o r , nor the buoyant flow down the c o r r i d o r . However, the computer f i r e code FAST, (2) s t a r t i n g with a given gaseous f u e l release rate i n a room, computes the d i s t r i b u t i o n of the r e s u l t a n t gases through a s e r i e s of i n t e r c o n n e c t i n g rooms. Since FAST only provides f o r f i v e rooms and no c o r r i d o r s , the present problem i s s o l v e d by d i v i d i n g the c o r r i d o r i n t o four, 11m (36 f t ) long rooms separated by vents the f u l l width of the c o r r i d o r and 2m (6.5 f t ) high. FAST c a l c u l a t e s the r e s u l t a n t hot l a y e r depth, temperature and composition i n each room (four of which are simulated p a r t s of the c o r r i d o r ) . (This c a l c u l a t i o n took 12 hours on an IBM-PC-AT.) Since the hot l a y e r i n the f i r e room, because of 02 starvation, contains up to 20 mass percent f u e l , and n e i t h e r FIRST nor FAST can burn t h i s f u e l i n the c o r r i d o r (which i s what r e a l l y happens), FAST was t o l d t o burn a l l of the f u e l i n the f i r e room so that a l l the a v a i l a b l e energy i s released, even though i n the wrong place, and i s d i s t r i b u t e d by FAST t o the four (simulated c o r r i d o r ) rooms. It was assumed that the alarm which sounded i n the f i r e room was b a r e l y a u d i b l e i n the s u i t e of rooms. Father and mother slowly awaken and prepare t o move (70 seconds). The computer program EXITT Q) was used which sends f a t h e r t o i n v e s t i g a t e the f i r e and then t o awaken the boy, mother t o get her baby and a l l to go down the c o r r i d o r t o escape. F i n a l l y , the computer program HAZARD (4) can compute the i n c a p a c i t a t i o n o r death of persons during an escape attempt. This program was not used because a more d e t a i l e d c a l c u l a t i o n i s needed f o r the f u t u r e and w i l l be i l l u s t r a t e d here. Results of I l l u s t r a t i v e Example —

The F i r e Dynamics

The rate of heat r e l e a s e i n the f i r e room i s shown i n Figure 2. The smoke at the c e i l i n g i s s u f f i c i e n t to sound the alarm at 109.2 seconds. The c h a i r burns out e a r l y . The bed and dresser, a f t e r being i g n i t e d at about 300 seconds, are soon l i m i t e d i n heat release by the l i m i t e d oxygen a v a i l a b l e . The p y r o l y s i s rate i s shown i n Figure 3. The l a y e r of hot smokey gas at the c e i l i n g has a maximum temperature of 1000° K, a maximum f u e l content of 20 percent, and a maximum carbon monoxide content of 5500 ppm, as shown i n Figure 4. The flow of hot gas out of, and f r e s h a i r i n t o , the f i r e room i s shown i n Figure 5. The f i r e room occupant wakes up and escapes at 121 seconds, 12 seconds a f t e r the alarm. He leaves the door open so f i r e gases s t a r t t o flow out. The outflow increases r a p i d l y t o 1.2 kg/sec while the inflow, somewhat l a t e r , reaches 1 kg/sec. The outflowing hot l a y e r gas c a r r i e s i t s f u e l content which reaches a maximum of about .22 kg/sec. When t h i s f u e l i s burned i n the c o r r i d o r at the open door, 4.4 Mw i s being r e l e a s e d . Compare t h i s t o the maximum of 1.68 Mw i n the f i r e room. The


EMMONS

71



6.

Time after

Ignition

Seconds

Figure 2. The r a t e of heat r e l e a s e , Mw, p r e d i c t e d f o r the f i r e room by computer f i r e code FIRST. The r e s u l t a n t heat r e l e a s e c o n s i s t s o f cont r i b u t i o n s from an upholstered c h a i r , a bed, and a d r e s s e r . These l a t t e r two show severe burning l i m i t a t i o n s by the l i m i t e d oxygen supply.



72 FIRE AND POLYMERS



6.

EMMONS

Figure 4. Temperature

73


Some p r o p e r t i e s o f the c e i l i n g hot l a y e r p r e d i c t e d by FIRST: (••••)

fuel pyrolyzate

(

K;

CO concentration

(

) ppm;

Unburned

) %.


74


FIRE AND POLYMERS

F i g u r e 5.

Flow through f i r e room door,

Upper hot l a y e r outflow pyrolyzate

(

);

(

kg/sec, p r e d i c t e d by FIRST:

) c o n t a i n i n g unburned

Lower c o l d l a y e r i n f l o w

(

flammable ).


6.

EMMONS


75


sudden change i n flow rates a t 300 seconds may look wrong, but i s cons i s t e n t with the f r e q u e n t l y observed pulse o f gas which occurs i n r e a l f i r e s as new heated f u e l r a p i d l y i g n i t e s . On F i g u r e 3 i s shown ( ) the mass p y r o l y s i s rate used i n computing the combustion product d i s t r i b u t i o n by FAST. FAST ignores oxygen s t a r v a t i o n so i t w i l l burn a l l the p y r o l y z e d f u e l i n t h e f i r e room i n s t e a d of burning the excess p y r o l y z a t e i n the c o r r i d o r . The hot t o x i c gases flow out along the c o r r i d o r c e i l i n g l e a v i n g a r e l a t i v e l y c o o l , nontoxic l a y e r of a i r r e t u r n i n g a t the f l o o r . The depth of t h i s c o l d l a y e r computed by FAST i s shown i n F i g u r e 6. The times and p o s i t i o n s at which the c o l d l a y e r i s deeper than 1.2 meters are shown (\ \ \ \ \ \ \ ) . In these p o s i t i o n s and times, an able adult can move at 1.3 m/sec t o escape. Only e a r l y i n the f i r e (before about three minutes) i s the c o l d l a y e r deep enough t o a v o i d crawling. The temperature o f the hot l a y e r i n the c o r r i d o r i s shown i n Figure 7. In the c o r r i d o r , the hot gas i s untenable f o r an upright person next t o the open f i r e room door a f t e r about 160 seconds. A f t e r about four minutes, the r a d i a t i o n from the hot l a y e r would be too high t o permit a person t o pass. Furthermore, i n a c t u a l f a c t , the temperature would be higher than t h a t c a l c u l a t e d a t the f i r e room door, because of the f u e l which would burn i n the c o r r i d o r , thus p r o v i d i n g flame temperature r a d i a t i o n i n a d d i t i o n t o the hot l a y e r temperature computed here. The carbon monoxide i n the c o r r i d o r i s shown on F i g u r e 8. The data on CO production, e s p e c i a l l y during oxygen s t a r v a t i o n , i s very inadequate. These computed values are probably too s m a l l . I t w i l l , nonetheless, serve as an i l l u s t r a t i v e example. Figures 6-8 c o n s t i t u t e the hazard maps f o r the escape route, i n t h i s case, the c o r r i d o r . The time l i n e f o r the f i r e i s given i n Table I. The Occupant Actions In the present example, the only f i r e d e t e c t o r i s i n the f i r e room. When i t alarms, the f i r e room occupant i s awakened immediately, but occupants i n the s u i t e can h a r d l y hear i t . They are slow t o respond. The program EXITT knows where a l l persons are, decides mother w i l l get baby, seeks the s h o r t e s t path t o get there and c a l c u l a t e s the time at 1.3 m/sec. Mother and baby then f o l l o w the shortest route t o the c o r r i d o r door. The times r e q u i r e d f o r these a c t i o n s are given i n Table I I . Simultaneously, the Father goes t o the c o r r i d o r door t o i n v e s t i g a t e the f i r e . I t i s bad. He decides t o r e t u r n t o awaken h i s son and they then go t o escape down the c o r r i d o r . Again, Table I I gives the time l i n e . Having a r r i v e d at the c o r r i d o r , can the s u i t e occupants make i t t o safety? Mother with baby a r r i v e s at time 286.4 seconds (Table I I ) . At t h i s time, the c o l d l a y e r at the f l o o r i s only .9 meter deep (Figure 6 ) . The corresponding hot l a y e r temperature i s about 335° K (62° C) (Figure 7), but the c o l d l a y e r temperature i s the o r i g i n a l low value. Also, the CO i s about 1000 ppm i n the l a y e r above. To escape, the mother must crawl t a k i n g 84.6 seconds t o reach the open end and s a f e t y . The l i n e A-A on F i g u r e s 6-8 show the c o n d i t i o n s during her escape. The f a t h e r and boy encounter c o n d i t i o n s on l i n e B-B. They must a l s o crawl i n order t o avoid breathing CO of 5000 ppm and a maximum temperature of 625° K (352° C), which i s l e t h a l . They w i l l a l l escape, i f they can remain low enough and are not i n c a p a c i t a t e d by r a d i a t i o n from the hot l a y e r over t h e i r heads. Mother encounters about 450° K (177° C) overhead f o r about 61 seconds, while f a t h e r and boy would have t o endure over 500° K (227° C) overhead f o r a minute with about 600° K (327° C) f o r 17 seconds. Mother and baby may make i t t o safety, but f a t h e r and boy w i l l probably succumb t o the high temperature r a d i a t i o n .


FIRE AND POLYMERS


76

Position along

Corridor

m

Figure 6. Height above the f l o o r of the i n t e r f a c e between the upper (hot) and lower (cold) l a y e r s i n the c o r r i d o r , m, p r e d i c t e d by FAST: (A-A) Mother-baby escape route; (B-B) Father-boy escape route; (\ \ \ \) Region where running i s p o s s i b l e ; (F-F) L a t e s t p o s s i b l e escape route without crawling.


6.

EMMONS

77


C


1000

ICT

20 ' 30 Position along Corridor m

40

F i g u r e 7. Hot l a y e r temperature i n c o r r i d o r , K, p r e d i c t e d by FAST: (A-A) Mother-baby escape route; (B-B) Father-boy escape route; (C-C) Path of overhead r a d i a t i o n temperature exposure f o r person, i f heat i n c a p a c i t a t e d at 20 m from e x i t ; (F-F) L a t e s t p o s s i b l e escape route without crawling; (\ \ \ \) Temperature not yet changed from ambient.


44

FIRE AND POLYMERS

78

1000

6.6 2000

900


6 800

5 5000

700

^ %

probable lethality

10 20 Position along Corridor F i g u r e 8. Carbon monoxide i n c o r r i d o r , ppm, p r e d i c t e d by FAST: (A-A) Mother and baby escape route; (B-B) Father and boy escape route; (D-D) Escape route through t o x i c but cooled l a y e r . Numbers show p r o b a b i l i t y o f i n c a p a c i t a t i o n l o c a t i o n . (E-E) Shows CO exposure f o r any person i n c a p a c i t a t e d (3.4%) 5 meters from the c o r r i d o r e x i t . Numbers show p r o b a b i l i t y o f death l o c a t i o n .


6.

EMMONS


79

Table I. Time Line of F i r e


time-seconds 0 109.2 121 160 185

I g n i t i o n of c h a i r (flaming s t a r t s ) P h o t o e l e c t r i c detector i n f i r e room alarms F i r e room occupant leaves and leaves door open Hot l a y e r a t end of c o r r i d o r f a l l s t o 1.2 meters from f l o o r Hot l a y e r i n c o r r i d o r by f i r e room door becomes i n c a p a c i t a t i n g T = 350° K (77° C)

277.4 278.3

Bed heated t o 520° K (247° C) i g n i t e s Bed f i r e oxygen starved — flames probably come out the f i r e room door at about t h i s time (hot l a y e r f u e l = 9.85%) Maximum CO i n the f i r e room, 5500 ppm

310 314.1 315.5 350 390 400 480 580

Dresser heated t o 600° K (327° C) i g n i t e s Dresser oxygen starved Maximum heat release rate i n room, 1.65 Mw Minimum depth of c o l d l a y e r i n f i r e room, .5 m Maximum CO i n c o r r i d o r 14,500 ppm Minimum depth of c o l d l a y e r i n c o r r i d o r .29 m Maximum temperature i n c o r r i d o r at f i r e room door, 1180° K (907° C) Maximum temperature at c o r r i d o r c l o s e d end, 710° K (437° C) Maximum temperature i n f i r e room, 1013° K (740° C) Bed ceases t o be oxygen s t a r v e d Dresser ceases t o be oxygen s t a r v e d Bed reduced t o l K g Dresser reduced t o lKg

610 770 772.5 845.3 953 -3000

Table I I .

Time Line o f Occupants

time-seconds 109.2 179 .2 183 .8 188,.8 193,.2 201,.8 203,.2 212..9 222,.9 232,.6 286,.4 317,.2

Alarm sounds i n f i r e room. Father and mother vaguely hear i t and are slow t o awake. (109,.2 + 70) Father and mother p a r t i a l l y dressed and s t a r t t o move. (179 .2 + 4.6) Mother gets baby. (183,.8 + 5) Mother s t a r t s t o e x i t with baby. (179..2 + 14) Father a r r i v e s at c o r r i d o r door t o investigate f i r e . (188,.8 + 13) Mother a r r i v e s at c o r r i d o r t o escape with baby. (193,.2 + 10) Father concludes the f i r e i s r e a l and returns t o get boy Father a r r i v e s i n boy's room. (203,.2 + 9.7) (212..9 + 10) Father awakens boy and s t a r t s t o e x i t . (222,.9 + 9.7) Father and boy a r r i v e at c o r r i d o r door. Mother with baby crawls t o e x i t door. (201,.8 + 84.6) (232..6 + 84.6) Father and boy crawl t o e x i t door.



80

FIRE AND POLYMERS

So long as they stay out of the hot l a y e r , the exposure t o t o x i c gas i s n e g l i g i b l e . We might note, however, i f Father and/or boy i s i n c a p a c i t a t e d by heat just at the end of the h o t t e s t overhead gas, i . e . , at 20 meters (66 f t ) from the open end of the c o r r i d o r , they would f a l l i n t o the c o l d l a y e r at the f l o o r and s t i l l r e c e i v e l i t t l e CO. However, they would encounter temperature r a d i a t i o n c o n d i t i o n s along l i n e C-C i n Figure 7. The maximum overhead temperature ranges up t o 950° K (677° C), more than enough to s e t t h e i r c l o t h i n g a f i r e . They would not s u r v i v e unless f i r e f i g h t e r s with b r e a t h i n g apparatus and a f o g nozzle got i n t o the c o r r i d o r w i t h i n a minute or so. To continue the i l l u s t r a t i o n of hazard c o n s i d e r a t i o n s , l e t us suppose that the CO composition of F i g u r e 8 i s encountered f l o o r t o c e i l i n g on an upper f l o o r where the gas had already been c o o l e d by heat t r a n s f e r t o b u i l d i n g and contents below so that no high temperature hazard e x i s t s . Suppose a person t r i e d t o escape at 365 seconds (Figure 8) where the CO encountered i s 10,000 ppm and he/she t r a v e l s at .5 m/sec along l i n e D-D. In t h i s process, the person would encounter CO, shown as D-D i n Figure 9. T h i s i s the exposure dose. The F r a c t i o n a l E f f e c t i v e Dose (FED) of t o x i c a n t r e c e i v e d by an exposed person i s d e f i n e d by H a r t z e l l (5, 6) as

FED =

2j 1

I - j ^

-

1

^

i = specie

(1)

1

tfc)

where f o r Incapacitation K (ppm) (sec) b (ppm) CO HCN

2.2 x 1 0 4.2 x 1 0

6

4

233 x V 92 '

Lethality K (ppm) (sec) b (ppm) 6.2 x 10

6

1.9 x 1 0

5

FEDI

1778 x > FEDL 66 '

Assuming the above c o e f f i c i e n t s from r a t data apply t o humans, a person w i l l have r e c e i v e d an IC50 or LC50 dose, i f the corresponding FED=1. When our knowledge of t o x i c hazard i s complete, there w i l l be a s i n g l e a l g o r i t h m f o r both i n c a p a c i t a t i o n and death since these e f f e c t s f o l l o w each other. However, f o r now, the FED approach which requires two separate c a l c u l a t i o n s , i s the l a t e s t advance. For persons f o l l o w i n g path D-D, Figure 8, they w i l l have r e c e i v e d an FEDI = 0.525 f o r i n c a p a c i t a t i o n and an FEDL = .170 f o r l e t h a l i t y by the time they reach the c o r r i d o r e x i t . The exposure i s f a r l e s s than a dose for 50 percent e f f e c t . What, i f anything, can be s a i d about the escapees c o n d i t i o n ? F i g u r e 10 i s drawn f o l l o w i n g H a r t z e l l e t a l . ' s suggestive f i g u r e (Figure 6 i n Ref. 7 ) . By t h i s f i g u r e , FEDI = .525 corresponds t o 5 percent i n c a p a c i t a t i o n , while FEDL = .17 corresponds t o a completely n e g l i g i b l e p r o b a b i l i t y of death. For each i n d i v i d u a l person, the p r o b a b i l i t y of escape i s 95 percent, with the percent p r o b a b i l i t y of being i n c a p a c i t a t e d along the escape path D-D, F i g u r e s 8 and 9, v a r y i n g as i n d i c a t e d by the small numbers. Once i n c a p a c i t a t e d , the person f a l l s t o the f l o o r and continues t o breath CO from the changing f i r e gases. I f a person f a l l s 5 meters (16 f t ) from the open end of the c o r r i d o r , f u r t h e r exposure occurs along the l i n e E-E i n F i g u r e 8. T h i s exposure i s a l s o p l o t t e d i n Figure 9. At the i n c a p a c i t a t i o n time (444 seconds, 5 m along c o r r i d o r ) , the l e t h a l dose i s



6.

EMMONS

0 300 1


1

400

1

500

81

1

1

1

"

600

700

800

900

Time after Ignition

Seconds

L

1000

F i g u r e 9. CO exposure experienced on escape route: (D-D) numbers are p r o b a b i l i t y of incapacitation; (E-E) CO exposure o f i n c a p a c i t a t e d person 5 meters from c o r r i d o r e x i t . Numbers are p r o b a b i l i t y o f death. Line a t 1778 ppm below which CO makes no c o n t r i b u t i o n t o death.


82

FIRE AND POLYMERS

100 %

Probability of Incapacitation $0 or Death


60 50 '

y /

.2

.4 FED

.6

.8

Baboon Oata o

20

1

1.2

1.4

1.6

1.8

for Incapaation or Death by Fire Gases

Figure 10. The percent p r o b a b i l i t y o f i n c a p a c i t a t i o n o r death as dependent on the corresponding F r a c t i o n a l E f f e c t i v e Dose (FED) d e f i n e d by Equation 1.

only FEDL = .17. As the FEDL increases along E-E, the p r o b a b i l i t y o f dying i n c r e a s e s as shown by the small numbers along E-E. As a l a s t i l l u s t r a t i o n , r e t u r n t o the o r i g i n a l problem o f F i g u r e 1 and ask. how much time the f a m i l y i n the s u i t e has, i f they are t o be able to s a f e l y run a t 1.65 m/sec t o e x i t a t the open end of the c o r r i d o r . In order t o run, the program HAZARD assumes that the h o t - c o l d i n t e r f a c e i s a t l e a s t 1.2 meters from the f l o o r . The l a t e s t they c o u l d leave the s u i t e i s at 160 seconds f o l l o w i n g the dashed l i n e F-F i n F i g u r e 6. In order t o get out of the s u i t e by 160 seconds, they must respond w i t h i n 160 - 109.2 = 50.8 seconds a f t e r the alarm sounds. T h i s i s not much time. I f there had been a s e l f - c l o s i n g door on the f i r e room, the c o r r i d o r would have been passable f o r a much longer p e r i o d and the f a m i l y c o u l d e a s i l y escape. Conclusions The i l l u s t r a t i v e examples could be produced only by using both f i r e dynamics and human f a c t o r information, which contains many crude a p p r o x i mations t o the r e a l world and omits completely many important e f f e c t s . However, i t i s c l e a r t h a t r e a l progress i s being made toward a t t a i n i n g a s u f f i c i e n t l y accurate p r e d i c t i v e understanding o f f i r e and i t s consequences so that a performance code can e v e n t u a l l y be a t t a i n e d . The computer f i r e codes need t o be made more comprehensive. There needs t o be a mechanism set up t o evaluate the v a l i d i t y of computer f i r e codes f o r use with a l e g a l performance code, j u s t as i s done with a l l other l e g a l codes. The t o x i c o l o g i c a l " f a c t s " I have used goes beyond present v a l i d a t e d knowledge and thus i n d i c a t e s d i r e c t i o n s t h a t f u t u r e work might take t o produce the data t h a t can a c t u a l l y be used i n a computer f i r e model.


6.

EMMONS

83


As soon as a r e a l l y Comprehensive Computer F i r e Code, i n c l u d i n g human r e a c t i o n s and hazard e f f e c t s , i s a v a i l a b l e , we w i l l be able t o o b t a i n t o x i c i t y data f o r humans. Every f i r e i n which there are deaths i s a t o x i c i t y t e s t run with no c o n t r o l . Surely, o f the 6000 o r so such f i r e s i n the U.S. every year, a few hundred w i l l be i n s u f f i c i e n t l y w e l l - d e f i n e d c o n d i t i o n s t h a t a comprehensive f i r e code w i l l be able t o p r e d i c t where the bodies should be found. I f the bodies are not found where expected, t h e rat data can be modified a p p r o p r i a t e l y .


Literature Cited 1.

Mitler, H.E. and Rockett, J.A. Users Guide to FIRST, A Comprehensive Single-Room Fire Model, NBSIR 87-3595, 1987.

2.

Walton, W.D.; Baer, S.R.; and Jones, W.W. NBSIR 85-3284, 1985.

3.

Levin, B.M. EXITT--A Simulation Model of Occupant Decisions and Actions in Residential Fires, User's Guide and Program Description, Appendix B, Reference 4.

4.

Bukowski, R.W.; Jones, W.W.; Levin, B.M.; Forney, C.L.; Stiefel, S.W.; Babrauskas, V.; Braun, E . ; and Fowell, A.J. HAZARD 1, Vol. 1, Fire Hazard Assessment Method, NBSIR 87-3602, 1987.

5.

Hartzell, G.E.; Priest, D.N.; and Switzer, W.G., Sciences 1985, 3(2): 115-128.

6.

Emmons, H.W., Fire Safety Journal

7.

Hartzell, G.E.; Grand, A.F.; Kaplan, H. L . ; Priest, M.S.; Stacy, H.W.; Switzer, W.G.; and Packham, S.C. Analysis of Hazards to Life Safety in Fires: A Comprehensive Multidimensional Research Program, Year 1, Final Report, SwRI Project 01-7606, NBS Contract NB83NADA4015.

Users Guide for FAST,

J . of Fire

1987, 12, 183-189.

RECEIVED November17,1989


Toxic Hazard and Fire Science - ACS Symposium Series (ACS

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