Fire Hazard in a Room Due to a Fire Starting in a ... - ACS Publications

Chapter 34

Fire Hazard in a Room Due to a Fire Starting in a Plenum

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on April 1, 2018 | https://pubs.acs.org Publication Date: May 9, 1990 | doi: 10.1021/bk-1990-0425.ch034

Effect of Poly(vinyl chloride) Wire Coating F. Merrill Galloway and Marcelo M. Hirschler BFGoodrich Technical Center, P.O. Box 122, Avon Lake, OH 44012 An issue of interest is the contribution to f i r e hazard in a room from products in a plenum space above i t . This contribution can result from two scenarios: f i r e in the room or f i r e in the plenum. The products being addressed here are PVC e l e c t r i c a l products contained in a plenum. The f i r s t scenario involves a f i r e starting in the room. Three room dimensions and two c e i l i n g materials were analysed; the products were PVC conduit (rigid and ENMT, semi-rigid; 100 m of either) and PVC wire coating (400 m). It was found that the amount of energy needed for the room f i r e to cause thermal decomposition of the PVC products in the plenum was larger than that needed to take the room to flashover. Furthermore, if the PVC products did eventually decompose or burn, somehow, they would cause a lethal smoke concentration only significantly later than a lethal (by toxicity) atmosphere had already been created by the f i r e i t s e l f . Thus, the PVC products did not add any significant f i r e hazard to that caused by the room f i r e . The next scenario is more complex: i t involves a f i r e starting in a plenum and has been analysed only for wire coating. Calculations were made, for many f i r e scenarios, in which the f i r e hazard model F . A . S . T . was used to simulate hazard to occupants of a standard room following a f i r e starting in a plenum above it. A t o t a l of 400 m of PVC wire coating was assumed to be present in the plenum. Its decomposition was made a function of the plenum temperature achieved. The f i r e ranged 0097-6156/90/0425-0592$06.00/0 © 1990 American Chemical Society

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


34.

GALLOWAY & HIRSCHLER

Effect ofPoly (vinylchloride) Wire Coating

between RHR of 50 and 500 kW; the heat of combustion of the f i r e varied between a standard value (20 kJ/g) and that of methane (57 kJ/g). Various vent connections between compartments and surroundings were used. The plenum temperature was never enough to decompose all the PVC wire coating. If the plenum was vented to the surroundings, almost no smoke entered the room. In an unvented plenum smoke entered the room but the f i r e burnt for a short period only: the level of oxygen was not enough for f u l l combustion. In extreme cases the f i r e generated enough heat for an untenable atmosphere in the room. In almost a l l single plenum cases studied the smoke flowing into the room was insufficient to generate a concentration lethal to man. Therefore, using such low heat release PVC wire coating products did not cause a significant increase in the f i r e hazard to occupants. I n o f f i c e b u i l d i n g s i t i s v e r y common t o h a v e p l e n u m s , i . e . s p a c e s a b o v e rooms where t h e a i r h a n d l i n g s y s t e m i s l o c a t e d , t o g e t h e r w i t h e l e c t r i c a l w i r e s and c a b l e s , as w e l l a s a b u n d a n t wood a n d o t h e r c o n s t r u c t i o n m a t e r i a l s . T h e s e c o n c e a l e d s p a c e s a r e u s u a l l y c a . 1 m (3 f t ) h i g h a n d a r e i n v i s i b l e f r o m t h e room b e l o w . I n t h e 1 9 8 0 » s y e a r s t h e r e h a s b e e n some c o n t r o v e r s y about t h e e f f e c t o f f i r e s i n v o l v i n g combustible products c o n t a i n e d i n such concealed spaces. This addresses the room-plenum s c e n a r i o b o t h when a f i r e s t a r t s i n t h e room and when a f i r e s t a r t s i n t h e p l e n u m a n d i n v e s t i g a t e s i t s s p r e a d i n t o t h e room b e l o w . In r e c e n t y e a r s t h e r e h a s b e e n much c o n t r o v e r s y s u r r o u n d i n g t h e i m p a c t o f smoke t o x i c i t y f o l l o w i n g a f i r e . T h i s h a s i n c l u d e d d i s c u s s i o n s r e g a r d i n g means t o m e a s u r e t o x i c p o t e n c y , b y one o f a v a r i e t y o f s m a l l - s c a l e methods, and how t o u s e t h e s e r e s u l t s t o e v a l u a t e f i r e hazard. T h e r e h a s b e e n , i n p a r t i c u l a r , much s p e c u l a t i o n r e g a r d i n g t h e h a z a r d s due t o c e r t a i n p l a s t i c s , t y p i c a l l y p o l y ( v i n y l chloride) (PVC). The present paper w i l l deal with this issue i n several stages. (1) A d d r e s s t h e i s s u e o f PVC f i r e p r o p e r t i e s , i n c l u d i n g smoke t o x i c i t y a n d h y d r o g e n c h l o r i d e d e c a y . (2) D e s c r i b e measurements o f mass l o s s r a t e s o f v a r i o u s electrical PVC products, by thermoanalytical experiments. (3) A d d r e s s t h e c o n c e a l e d s p a c e s c e n a r i o s u s e d . (4) I n v e s t i g a t e t h e f i r e h a z a r d i n a room d u e t o t h e b u r n i n g o f PVC e l e c t r i c a l p r o d u c t s i n a p l e n u m s p a c e


593

594

FIRE AND POLYMERS above i t , when a fire starts i n t h e compartment underneath. (5) I n v e s t i g a t e t h e f i r e h a z a r d i n a room due t o t h e b u r n i n g o f PVC w i r e c o a t i n g i n a p l e n u m s p a c e a b o v e i t , when t h e f i r e s t a r t s i n t h e plenum.


Fire

Properties of Poly(Vinyl Chloride)

O t h e r p a p e r s i n t h i s volume a d d r e s s t h e i m p o r t a n c e o f a v a r i e t y o f f i r e p r o p e r t i e s on f i r e h a z a r d , i n p a r t i c u l a r the r e l a t i v e importance (or l a c k o f i t ) o f t o x i c potency o f smoke ( e . g . R é f . [ 1 ] ) . PVC i s u n i q u e among commodity m a t e r i a l s i n t h a t i t c o n t a i n s c h l o r i n e and, t h u s , p r o d u c e s h y d r o g e n chloride (HC1) when i t decomposes o r b u r n s [ 2 , 3 ] . The fire properties o f PVC h a v e been put into p e r s p e c t i v e r e c e n t l y [4, 5 ] . They show t h a t PVC i s a polymer with a high ignition temperature and low flammability. F u r t h e r m o r e , PVC p r o d u c t s a r e a s s o c i a t e d w i t h a low r a t e o f h e a t r e l e a s e a s w e l l a s l i t t l e total heat released [4-9]. T h i s w i l l depend, c l e a r l y , on t h e type of product, since plasticised PVC p r o d u c t s a r e o b v i o u s l y more f l a m m a b l e t h a n r i g i d o n e s . Undoubtedly, f i r e hazard i s p a r t i a l l y a s s o c i a t e d w i t h t h e t o x i c i t y o f t h e smoke i t s e l f . The smoke o f a v a r i e t y of common m a t e r i a l s , a s m e a s u r e d e . g . by t h e NBS c u p furnace t o x i c i t y test [ 1 0 ] , h a s r e c e n t l y b e e n compared w i t h t h e i n t r i n s i c t o x i c p o t e n c y o f o t h e r p o i s o n s and o f t o x i c gases, as w e l l as w i t h t o x i c i t y c a t e g o r i e s [11]. I t h a s b e e n shown t h a t t o x i c i t y i s a r e l a t i v e l y m i n o r f a c t o r because there i s very little difference between t h e i n t r i n s i c t o x i c p o t e n c y o f t h e smoke o f t h e m a j o r i t y o f common m a t e r i a l s , w i t h v e r y few e x c e p t i o n s . D e t a i l e d s t u d i e s h a v e a l s o b e e n made on t h e t o x i c i t y o f HC1, a n i r r i t a n t g a s o f t e n p r e s e n t i n f i r e s . I t does n o t c a u s e baboon o r r a t i n c a p a c i t a t i o n up t o v e r y h i g h exposure doses which a r e s u f f i c i e n t (or very close) t o cause e v e n t u a l death [ 1 2 ] . Furthermore, a r e c e n t study has shown t h a t the e f f e c t s of i r r i t a n t s are heavily d e p e n d e n t on t h e a n i m a l model u s e d [ 1 3 ] . I n t e r e s t i n g l y , t h e mouse i s much more s e n s i t i v e t o HC1 t h a n t h e r a t [ 1 3 - 1 6 ] , I n t u r n , however, t h e r a t w o r k s as a g o o d model f o r a p r i m a t e , a s f a r a s l e t h a l i t y due t o HC1 i s c o n c e r n e d [17, 1 8 ] . T h i s i s i m p o r t a n t b e c a u s e a l l r o d e n t s (mice and r a t s ) a r e o b l i g a t e n o s e b r e a t h e r s , w h i l e p r i m a t e s c a n a l s o b r e a t h e t h r o u g h t h e i r mouths, a n d i t h a s been speculated that this would make rodents less s e n s i t i v e t o HC1 t h a n p r i m a t e s [ 1 9 ] . The r e l e v a n c e o f a l l t h i s t o t h e p r e s e n t p a p e r i s t h a t t h e t o x i c p o t e n c y o f PVC smoke o r o f HC1 a r e f a i r l y s i m i l a r t o t h o s e o f o t h e r smoke o r o f c a r b o n m o n o x i d e (CO) respectively.



34.


Effect ofPoly(vinyl chloride) Wire Coating

A l a r g e number o f s t u d i e s h a v e a l s o b e e n done t o i n v e s t i g a t e t h e l i f e t i m e o f HC1 i n a f i r e atmosphere [20-24]. T h e s e s t u d i e s h a v e shown t h a t HC1 r e a c t s v e r y r a p i d l y w i t h most common c o n s t r u c t i o n s u r f a c e s (cement b l o c k , c e i l i n g t i l e , gypsum b o a r d , e t c . ) s o t h a t t h e peak atmospheric c o n c e n t r a t i o n f o u n d i n a f i r e i s much l e s s t h a n w o u l d h a v e been p r e d i c t e d f r o m t h e c h l o r i n e c o n t e n t of the burning material. Furthermore, this peak c o n c e n t r a t i o n s o o n d e c r e a s e s a n d HC1 d i s a p p e a r s c o m p l e t e l y from t h e atmosphere. These c o n s i d e r a t i o n s a r e i n c l u d e d here because i n t h e d i s c u s s i o n t h a t f o l l o w s HC1 d e c a y w i l l be i g n o r e d , t o f a c i l i t a t e the calculations. HC1 d e c a y i s a l s o i m p o r t a n t when m e a s u r i n g PVC t o x i c p o t e n c y , because t h e w a l l s o f e x p o s u r e chambers a r e made o f n o n - s o r p t i v e m a t e r i a l s , where s u c h d e c a y i s m i n i m i s e d . In t h i s connection i t i s worth p o i n t i n g out t h a t t h e h i g h e s t c o n c e n t r a t i o n o f HCl f o u n d when f i r e f i g h t e r s e n t e r e d b u i l d i n g s a c t u a l l y on f i r e was c a . 280 ppm [25, 2 6 ] . Mass L o s s

R a t e s o f PVC

Products

Table I presents the r e s u l t s of "isothermal" simultaneous t h e r m o a n a l y t i c a l (STA) r u n s , a t 573 Κ a n d 773 K, f o r a l l three products. S i m i l a r data, a t a f i x e d heating r a t e i s shown i n T a b l e I I . One o f t h e c r u c i a l p a r a m e t e r s i s t h e t e m p e r a t u r e o f maximum w e i g h t l o s s r a t e , c o r r e s p o n d i n g t o t h e t i m e when d e h y d r o c h l o r i n a t i o n o f PVC s t a r t s b e c o m i n g important. T h i s temperature i s c l o s e t o 573 Κ i n a l l cases. In f a c t , a t a r e l a t i v e l y f a s t h e a t i n g r a t e , almost no d e c o m p o s i t i o n o c c u r s a t t e m p e r a t u r e s u n d e r 563 K. If t h e m a t e r i a l s a r e h e a t e d a t 573 Κ f o r a p r o l o n g e d p e r i o d , c o m p l e t e d e h y d r o c h l o r i n a t i o n t a k e s p l a c e , b u t no f u r t h e r s t a g e s o f PVC d e c o m p o s i t i o n o c c u r . None o f t h e three materials investigated decomposes completely until a t e m p e r a t u r e o f c a . 773 Κ i s a t t a i n e d . Even t h e n o n l y a c e r t a i n f r a c t i o n o f t h e e n t i r e mass o f t h e s a m p l e s i s v o l a t i l i s e d , due t o t h e p r e s e n c e o f i n o r g a n i c f i l l e r s i n t h e i r composition. The a v e r a g e r a t e o f mass l o s s i s c a l c u l a t e d f r o m t h e amount o f mass l o s t a n d t h e c o r r e s p o n d i n g t i m e p e r i o d . The c a l c u l a t i o n s i n T a b l e I a t 573 Κ r e p r e s e n t t h e a v e r a g e mass l o s s o f i s o t h e r m a l d e h y d r o c h l o r i n a t i o n . Thus, t h e v a l u e s i n T a b l e I (3.4 %/min f o r b l u e c o n d u i t , 2.9 %/min f o r g r e y c o n d u i t and 2.3 %/min f o r w i r e c o a t i n g ) r e p r e s e n t a r e a s o n a b l e e s t i m a t e o f t h e mass l o s s r a t e o f t h e PVC p r o d u c t s i n a f i r e , a t a t e m p e r a t u r e n o t e x c e e d i n g 563 K. Concealed

Space

Scenarios

A few r e c e n t e v e n t s make i t p a r t i c u l a r l y i n t e r e s t i n g t o v a l u a t e t h e f i r e h a z a r d r e s u l t i n g f r o m t h e b u r n i n g o f PVC m a t e r i a l s , when t h e y a r e p r e s e n t i n a p l e n u m . These i n c l u d e t h e r e c e n t r e g u l a t i o n s promulgated i n New Y o r k S t a t e r e g a r d i n g t h e c r e a t i o n o f a d a t a b a s e f o r smoke


595


wt l o s s

255

First

T (K)

Max DTG

(%)

(mg/min)

(%)

(mg/min)

T h i r d wt l o s s

Max DTG

S e c o n d wt l o s s

(%/min) loss)

(%/min)

Max DTG

(%)

(mg/min)

A v e r a g e DTG ( f i r s t wt

Κ

(%)

Max DTG

U

wt l o s s

Total

Top T e m p e r a t u r e

Table I.

2.0

3.4

10.8

2.6

290

49.0

51.0

573

0.3

14.6

1.8

20.5

14.3

34.2

7.5

279

56.0

85.9

873

ENMT C o n d u i t

2.9

13.1

3.1

290

50.1

50.1

573

Rigid

Results of "isothermal"

0.06

22.9

0.2

18.7

12.5

29.3

6.1

269

47.7

85.5

873

Conduit

STA r u n s

-

-

-

-

2.3

7.9

1.9

282

49.9

49.9

573

Wire

0.04

6.5

0.9

8.8

10.5

35.6

7.8

46.6

62.0

873

Coating



34.



t o x i c i t y of b u i l d i n g products [27]. The p r o d u c t s t h a t were t e s t e d i n t h e f i r s t y e a r ( e l e c t r i c a l ) a r e o f t e n f o u n d behind f i r e rated w a l l s or c e i l i n g s . An example o f a c a l c u l a t i o n o f t h i s t y p e h a s b e e n made f o r f l u o r i n a t e d w i r e c o a t i n g s [28] and f o r PVC e l e c t r i c a l m a t e r i a l s [29] and, a n o t h e r one, f o l l o w i n g a d i f f e r e n t p r o c e d u r e and a d i f f e r e n t s c e n a r i o , f o r PVC-based e l e c t r i c n o n - m e t a l l i c (ENMT, s e m i - r i g i d ) c o n d u i t [ 3 0 ] . The p h i l o s o p h y u s e d i n r e f e r e n c e s [28] and [29] i s t h a t f i r e h a z a r d i s h i g h e r i f t h e time t o r e a c h a l e t h a l atmosphere i s lower. The scenarios investigated here involve various room-plenum c o n f i g u r a t i o n s . The room h a s a standard opening c o r r e s p o n d i n g t o the s i z e of a normal door (2.03 χ 0.74 m). The rooms i n t h e f i r s t p a r t o f t h e s t u d y ( f i r e i n t h e room) were o f d i m e n s i o n s w h i c h m i g h t r e p r e s e n t , a p p r o x i m a t e l y , a s m a l l w a r e h o u s e (10.0 χ 10.0 χ 3.0 m), a bedroom ( 3 . 7 x 3 . 7 x 2 . 7 m) and an o f f i c e (2.5 χ 2.5 χ 2.5 m) and t h e p l e n u m h e i g h t i s 1.0 m t h r o u g h o u t . In each c a s e , two different c e i l i n g m a t e r i a l s were c o n s i d e r e d (viz. gypsum w a l l b o a r d (GB) and ceiling tile (CT)). Furthermore, the i n t e n s i t y of heat of combustion of the f u e l i n v o l v e d i n c a u s i n g t h e f i r e was s e t a t b o t h 20 k J / g and 40 k J / g , t h u s c o v e r i n g t h e r a n g e s t y p i c a l f o r most materials. I t was assumed t h a t t h e smoke was i n s t a n t a n e o u s l y d i s t r i b u t e d among e i t h e r t h e room and p l e n u m o r t h e room and p l e n u m p l u s a n o t h e r t h r e e rooms i d e n t i c a l i n s i z e t o t h e b u r n room. A l l room w a l l s were assumed t o be made o f gypsum w a l l b o a r d and a l l f l o o r s o f c o n c r e t e . This part w i l l p r e s e n t , f o r e a c h c a s e , an a s s e s s m e n t of the time required to achieve an untenable atmosphere, as a consequence of the exclusive presence, in the c o r r e s p o n d i n g plenum, o f P V C - c o a t e d e l e c t r i c a l w i r e (400 m) , o f P V C - b a s e d r i g i d c o n d u i t (100 m) and o f P V C - b a s e d e l e c t r i c a l n o n - m e t a l l i c ENMT, s e m i - r i g i d , c o n d u i t (100 m). T h e s e t i m e s w i l l be compared w i t h t h e t i m e s a t w h i c h s u c h an u n t e n a b l e a t m o s p h e r e i s g e n e r a t e d due t o t h e t o x i c i t y o f t h e m a t e r i a l s b u r n i n g i n t h e room, a s s u m i n g them t o be o f n o r m a l t o x i c p o t e n c y , s i m i l a r t o t h a t o f an o r d i n a r y wooden p r o d u c t ( e . g . D o u g l a s f i r ) . The rooms i n t h e s e c o n d p a r t o f t h e s t u d y a r e a l l o f t h e same s i z e , v i z . 3.7 χ 3.7 χ 2.7 m. The p l e n u m s b e i n g c o n s i d e r e d a r e e i t h e r one w i t h t h e same f l o o r s i z e and 1.0 m h e i g h t o r one w i t h 3 t i m e s t h e f l o o r s i z e (3 p l e n u m configuration) o r 10 t i m e s t h e f l o o r size (10 p l e n u m configuration). The o n l y c e i l i n g m a t e r i a l c o n s i d e r e d i s gypsum b o a r d and t h e o n l y p r o d u c t b e i n g i n v e s t i g a t e d i s a PVC w i r e c o a t i n g f i r e r e t a r d e d t o g i v e v e r y low heat r e l e a s e and f l a m e s p r e a d . In t h i s case, the f i r e s t a r t s i n a p l e n u m and t h e work i n v e s t i g a t e s w h e t h e r i t s p r e a d s into the room below in terms of i t s effects on temperature, smoke l a y e r l e v e l s and c o n c e n t r a t i o n s of t o x i c g a s e s , m a i n l y c a r b o n monoxide, i n b o t h room and plenum.


597

Nelson; Fire and Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1990. 57.6

DTG

DTG

S e c o n d wt

loss

(%)

(%/min) loss)

(K)

(%/min)

A v e r a g e DTG ( f i r s t wt

Temp max

1%

22.9

1.7

546

13.5

(%)

92.0

5

Max

loss

(%)

K/min

16.8

7.4

578

33.3

500

57.8

91.9

20

ENMT C o n d u i t

11.1

1.3

555

8.0

528

52.9

86.9

5

Rigid

17.0

6.1

574

31.1

575

53.2

87.6

20

Conduit

rate

15.1

1.1

568

8.6

595

50.7

77.6

5

12. 1

15.6

584

25.3

50.2

75.4

20

Wire Coating

R e s u l t s o f STA r u n s a t 5 a n d 20 K/min h e a t i n g

546

wt

First

loss

rate

II.

T ( K ) 522

wt

Total

Heating

Table


00

in


(%/min)

(%/min)

2.3

818

A v e r a g e DTG (%/min) 1.1 ( f i r s t t o t h i r d wt 1. s s e s )

727

2.4

24.2

1.1

(%/min) loss)

1.0

13.9

losses)

5.6

3.0

713

7.2

0.5

A v e r a g e DTG ( t h i r d wt

Temp max DTG (K)

Max DTG

(%)

1.3

A v e r a g e DTG (%/min) ( f i r s t a n d s e c o n d wt

T h i r d wt l o s s

0.9

696

1.5

A v e r a g e DTG (%/min) ( s e c o n d wt l o s s )

Temp max DTG (K)

Max DTG

1.1

1.0

787

1.9

22.9

1.2

0.9

712

2.7


600


Fire

FIRE AND starting

POLYMERS

i n t h e Room

For t h e a n a l y s i s , a s t e a d y - s t a t e f i r e was assumed. A s e r i e s o f e q u a t i o n s was t h u s u s e d t o c a l c u l a t e v a r i o u s temperatures and/or heat r e l e a s e r a t e s per u n i t s u r f a c e , b a s e d on a s s i g n e d i n p u t v a l u e s . T h i s s e r i e s o f e q u a t i o n s i n v o l v e s f o u r c o n v e c t i v e h e a t t r a n s f e r and two c o n d u c t i v e heat t r a n s f e r processes. These a r e : (a) c o n v e c t i v e t r a n s f e r f r o m f i r e t o u p p e r room l a y e r (b) c o n d u c t i v e t r a n s f e r t h r o u g h s u s p e n d e d c e i l i n g t o plenum f l o o r (c) convective transfer from suspended ceiling to plenum a i r (d) c o n v e c t i v e t r a n s f e r t o p l e n u m c e i l i n g (e) c o n d u c t i v e t r a n s f e r t h r o u g h c o n c r e t e p l e n u m c e i l i n g slab ( f ) c o n v e c t i v e t r a n s f e r t o a i r a b o v e plenum (ambient temperature) The h e a t r e l e a s e r a t e n e c e s s a r y f o r f l a s h o v e r was c a l c u l a t e d , f r o m t h e e q u a t i o n g i v e n by Q u i n t i e r e e t a l . [31]. The s e r i e s o f e q u a t i o n s i s t h e n s o l v e d , w i t h t h e assumption t h a t the temperature i n c r e a s e f o r f l a s h o v e r i s 500 Κ ( l e a d i n g t o an u p p e r l e v e l t e m p e r a t u r e o f T : 795 K) and t h e p l e n u m t e m p e r a t u r e f o r d e c o m p o s i t i o n o f t h e PVC p r o d u c t s i s 573 K. The r e s u l t s i n T a b l e I I I show t h a t a much more i n t e n s e f i r e i s r e q u i r e d , i n a l l c a s e s , t o c a u s e t h e PVC p r o d u c t s t o u n d e r g o d e h y d r o c h l o r i n a t i o n t h a n t o t a k e t h e room t o f l a s h o v e r . T h u s , t h e h e a t r e l e a s e d by this fire at flashover is insufficient to d e h y d r o c h l o r i n a t e t h e PVC p r o d u c t s i n t h e plenum, f o r any of the s c e n a r i o s . T h e r e f o r e , t h e o c c u p a n t s o f t h e room w i l l succumb b e f o r e t h e r e i s an e f f e c t due t o t h e p l e n u m PVC p r o d u c t s . I t i s of i n t e r e s t t o c a l c u l a t e , too the time r e q u i r e d f o r b o t h t h e f i r e i t s e l f and t h e t h e r m a l d e c o m p o s i t i o n o f t h e p l e n u m PVC p r o d u c t s t o p r o d u c e a l e t h a l a t m o s p h e r e . Table I I I p r e s e n t s such r e s u l t s f o r the f i r e , f o r heats of c o m b u s t i o n o f 20 k J / g and 40 k J / g , a r a n g e t y p i c a l o f most fires. In o r d e r t o c a r r y out t h i s c a l c u l a t i o n i t i s assumed t h a t t h e smoke i s d i s t r i b u t e d i n s t a n t a n e o u s l y throughout the volume being c o n s i d e r e d , one or four room-plenums. The barriers r e p r e s e n t e d by walls or transport processes are ignored. The t o x i c p o t e n c y u s e d f o r t h e f i r e i s a m i n i m a l v a l u e , an L C o f 40 mg/1 for a 30 min e x p o s u r e i n t h e NBS smoke t o x i c i t y t e s t , i n t h e n o n - f l a m i n g mode. T h i s c o u l d be r e p r e s e n t a t i v e o f a v a r i e t y o f m a t e r i a l s ( e . g . wood) and i s w i t h i n t h e n o r m a l range of t o x i c p o t e n c i e s . In order to calculate the "time to lethal c o n c e n t r a t i o n " t h e c o n c e n t r a t i o n o f smoke ( p e r u n i t t i m e ) is f i r s t calculated. Then t h e t o t a l amount o f smoke ( i n c o n c e n t r a t i o n p e r u n i t t i m e ) i s c a l c u l a t e d f r o m t h e mass o f m a t e r i a l (and, i n t h e c a s e o f t h e PVC p r o d u c t s , t h e percentage of the weight of the product t h a t can be v o l a t i l i s e d , a s s e e n f r o m t h e STA r e s u l t s ) . To t h e r a t i o UL

? 0



34.


Effect of Poly (vinyl chloride) Wire Coating

o f t h e t o x i c p o t e n c y t o t h e amount o f smoke i s a d d e d t h e time f o r thermal p e n e t r a t i o n of hot gases through the ceiling and t h e 30 min exposure time t h a t the toxic potency r e f e r s t o . The c a l c u l a t i o n s a r e a l l r e p e a t e d f o r t r a n s p o r t o f t h e smoke o v e r f o u r room-plenums o f t h e same size. Table I I I presents the r e s u l t s of c a l c u l a t i n g the " t i m e t o l e t h a l c o n c e n t r a t i o n " f o r e a c h one o f t h e PVC products investigated. The t o x i c p o t e n c y v a l u e s u s e d f o r a l l t h e m a t e r i a l s a r e b a s e d on 30 min e x p o s u r e s i n t h e NBS cup f u r n a c e t o x i c i t y t e s t , i n t h e N o n - F l a m i n g mode, t h e one most r e l e v a n t t o t h i s s c e n a r i o . I t i s c l e a r t h a t the "time t o l e t h a l c o n c e n t r a t i o n " f o r t h e smoke f r o m any o f t h e PVC p r o d u c t s i n t h e plenum, i n a l l t h e s i x s c e n a r i o s c o n s i d e r e d , i s much l o n g e r t h a n t h e t i m e r e q u i r e d f o r t h e f u e l i n t h e room i t s e l f t o c a u s e a l e t h a l c o n c e n t r a t i o n i n t h e same s c e n a r i o . T h i s i n d i c a t e s c l e a r l y t h a t t h e s e PVC plenum p r o d u c t s w i l l not cause a s e r i o u s f i r e hazard concern u n t i l w e l l a f t e r t h e f i r e i t s e l f h a s r e a c h e d f l a s h o v e r c o n d i t i o n s and has l o n g s i n c e caused l e t h a l c o n c e n t r a t i o n s , both i n t h e room o f o r i g i n and i n o t h e r rooms. I t i s w o r t h s t r e s s i n g t h a t t h e c a l c u l a t i o n s done i n t h i s work h a v e i g n o r e d HC1 d e c a y . T h i s i s very important s i n c e t h e r a t e o f HC1 d e c a y i n s o r p t i v e s u r f a c e s ( s u c h a s concrete or c e i l i n g t i l e ) i s extremely high (half l i v e s of HC1 o f l e s s t h a n 1 min h a v e b e e n c a l c u l a t e d f o r a p l e n u m w i t h such s u r f a c e s [32]). The same c a l c u l a t i o n p r o c e d u r e h a s a l s o b e e n a p p l i e d t o o t h e r p r o d u c t s i n t h e same s c e n a r i o . I n p a r t i c u l a r , i t has been used f o r PTFE w i r e coating i n one of the s c e n a r i o s b e i n g c o n s i d e r e d h e r e [28, 2 9 ] . The results showed t h a t , e v e n i f t h e t o x i c p o t e n c y o f t h e p r o d u c t i n t h e plenum i s e x t r e m e l y h i g h , i t i s e x t r e m e l y u n l i k e l y t o contribute s i g n i f i c a n t l y to f i r e hazard i n the h a b i t a b l e a r e a s i f i t h a s v e r y good f i r e performance. Fire

starting

i n the

Plenum

In t h i s c a s e a c o m p l e t e l y d i f f e r e n t a p p r o a c h was taken. I t was d e c i d e d t o u s e a f i r e m o d e l , o f z o n a l t y p e , t o p r e d i c t smoke f l o w s , t e m p e r a t u r e s and g a s c o n c e n t r a t i o n s . The model c h o s e n f o r t h e s e c a l c u l a t i o n s was t h e NBS Fire and Smoke T r a n s p o r t model ( F . A . S . T . ) , v e r s i o n 18.3 [ 3 3 ] . T h i s model r e q u i r e s t h a t t h e t r a n s p o r t between rooms be i n a h o r i z o n t a l manner. In order t o achieve t h i s , a v i r t u a l room i s n e e d e d and a v e n t i s n e e d e d i n b o t h t h e room and t h e plenum. In order, t h e r e f o r e , t o a n a l y s e a broad v a r i e t y o f d i f f e r e n t f i r e s and s c e n a r i o s , t h e o n l y p r o d u c t u s e d was a low h e a t r e l e a s e w i r e c o a t i n g . The p r o d u c t u s e d f o r t h e s e c a l c u l a t i o n s was a f i r e r e t a r d e d p l a s t i c i z e d PVC w i r e c o a t i n g m a t e r i a l , w h i c h d o e s n o t s p r e a d f l a m e o r c o n t i n u e b u r n i n g u n l e s s an e x t e r n a l source of heat or flame i s d i r e c t e d a t i t . This material was c h o s e n b e c a u s e PVC r e p r e s e n t s t h e most common c a b l e


601

Nelson; Fire and Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1990. 3. 7 3. 7 2. 7

D

5 0

H

o

f

5 0

I f f u e l h a s D e l t a con*> 40 k J / g a n d L C (30 min) Time t o l e t h a l c o n e , ( s ) 224 196 85 73 I f t h e v o l u m e c o n s i d e r e d i n c l u d e s f o u r rooms Time t o l e t h a l c o n e , ( s ) 895 782 339 293

H

Of

of

CT 295 795 0. 86 573 978 1. 40

Alone

GB 295 795 0.89 573 902 1.21

3.7 3.7 2.7

C

i n Room

Fire Fuel

CT 295 795 2.01 573 978 3.27

10.0 10.0 3.0

Β

E f f e c t o f Room

GB 295 795 2. 09 573 902 2. 86

10. 0 10. 0 3. 0

A

Fire

I f f u e l h a s D e l t a con*> Of 20 k J / g a n d L C (30 min) Time t o l e t h a l c o n e , ( s ) 112 98 42 37 I f t h e v o l u m e c o n s i d e r e d i n c l u d e s f o u r rooms Time t o l e t h a l c o n e , ( s ) 448 391 170 147

UL

UL

Susp. c e i l , m a t e r i a l Τ a m b i e n t (K) T a t f l a s h o v e r (K) RHR f l a s h o v e r (MW) Τ plenum (PVC d e c ) (K) T (PVC d e c ) (K) RHR r e q u d (PVC d e c ) (MW)

Room l e n g t h (m) Room w i d t h (m) Room h e i g h t (m)

Scenario

Table I I I .

34 138

160

69

80 40 mg/1 40

17

CT 295 795 0. β: 573 978 1. o;

2. 5 2. 5 2. 5

F

4 0 mg/1 20

GB 295 795 0.64 573 902 0.88

2.5 2.5 2.5

Ε



5 0

conduit

(100 m; 5 0

5 0

1422

664

mg/L)

1102

(100 m ; L C : 3 2 . 4

1962 1982 644 Time t o l e t h a l c o n e , ( s ) I f t h e v o l u m e c o n s i d e r e d i n c l u d e s f o u r rooms 6675 6695 1402 Time t o l e t h a l c o n e , (s)

PVC ENMT c o n d u i t

mg/L)

584

L C : 37 . 0

564 Time t o l e t h a l c o n e , ( s ) 1465 1485 i n c l u d e s f o u r rooms I f the volume c o n s i d e r e d 1082 Time t o l e t h a l c o n e , (s) 4687 4707

PVC r i g i d

659

mg/L)

3200

(400 m ; L C : 31. 6

639 1928 1948 Time t o l e t h a l c o n e , ( s ) i n c l u d e s f o u r rooms I f t h e volume c o n s i d e r e d 3180 Time t o l e t h a l c o n e , ( s ) 8339 8356

PVC w i r e c o a t i n g



604

FIRE AND POLYMERS

coating material used overall, although the fire characteristics of the particular example chosen a r e b e t t e r t h a n t h o s e o f t h e a v e r a g e p l a s t i c i z e d PVC. Plenum c a b l e s a r e , o f c o u r s e , v e r y o f t e n a l s o made o f f l u o r i n a t e d materials. A t o t a l o f 400 m o f t h e PVC w i r e were assumed t o be p r e s e n t i n a plenum. C a l c u l a t i o n s were made f o r many f i r e s c e n a r i o s . T h e s e v a r i e d i n f i r e s i z e a n d i n t h e burning c h a r a c t e r i s t i c s of the material burning i n the fire. I n v i e w o f t h e good f i r e p e r f o r m a n c e o f t h e w i r e coating itself, i t was p o s s i b l e t o i g n o r e t h e m i n u t e p r o b a b i l i t y o f i t being t h e item f i r s t i g n i t e d . A f r a c t i o n a l f a c t o r i a l d e s i g n was u s e d t o e x a m i n e t h e effects of 9 variables which were thought t o be significant. The v a r i a b l e s were: • F i r e heat • F i r e heat

release rate o f combustion

A set of five variables relating t o s i z e and o r i e n t a t i o n o f v e n t s c o n n e c t i n g p l e n u m a n d room ( t o p s o f p l e n u m v e n t and plenum a n d o f room v e n t a n d room c o i n c i d e ) • • • • •

Width o f Width o f Location Width o f Location

A set orientation surroundings • Vent • Vent

a d u c t c o n n e c t i n g room a n d p l e n u m v e n t i n plenum o f b o t t o m o f v e n t i n plenum v e n t i n room o f b o t t o m o f v e n t i n room

o f two v a r i a b l e s relating to size of single vent connecting room ( b o t t o m s o f v e n t a n d room c o i n c i d e )

and and

width height

T h r e e f i r e s i z e s were c h o s e n : 50, 275 a n d 500 kW, a n d t h e h e a t s o f c o m b u s t i o n p i c k e d , v i z . 20, 40 a n d 57 k J / g , r e p r e s e n t a s p r e a d between t h e n o r m a l h e a t o f c o m b u s t i o n o f most common m a t e r i a l s (20 kJ/g) a n d t h a t o f methane (57 kJ/g) . T h i s c o v e r s a v e r y wide range o f f i r e s and o f combustible materials s t a r t i n g the f i r e . In o r d e r t o c o v e r t h e s e n i n e v a r i a b l e s a d e q u a t e l y , a s t a t i s t i c a l e x p e r i m e n t a l d e s i g n was c a l c u l a t e d . The s t a t i s t i c a l e x p e r i m e n t a l d e s i g n r e q u i r e s t h e u s e o f 15 simulations f o r each plenum size. Simulations were r e p e a t e d u s i n g 3 and 10 p l e n u m s . The N a t i o n a l B u r e a u o f S t a n d a r d s (NBS, now N a t i o n a l I n s t i t u t e f o r Standards and Technology, NIST) f i r e a n d smoke t r a n s p o r t m o d e l , F.A.S.T., v e r s i o n 18.3, was u s e d t o g e n e r a t e t h e i n f o r m a t i o n c o n c e r n i n g t h e temperatures and gas c o n c e n t r a t i o n s . T h i s i s a zone model w h i c h p r e d i c t s t h e f o r m a t i o n o f two l a y e r s i n e a c h compartment. Once t h e c o n d i t i o n s g e n e r a t e d by e a c h f i r e were known, d e c i s i o n s were t a k e n a s t o w h i c h f i r e s w o u l d c a u s e s i g n i f i c a n t decomposition of these cables. Some e x a m p l e s


34.


Effect ofPoly (vinyl chloride) Wire Coating

o f s u c h c a s e s were t h e n r u n , where i t was assumed, f o r simplicity, that the PVC generated, initially, only hydrogen chloride (HC1). The r a t e o f HC1 generation i n c o r p o r a t e d i n t o e a c h example was c a l c u l a t e d b a s e d on t h e temperatures a c h i e v e d i n t h e plenum, a s p r e d i c t e d by F.A.S.T. HC1 d e c a y was i g n o r e d , a s a f i r s t a p p r o x i m a t i o n , j u s t a s i t had been i n t h e o t h e r s e t o f c a s e s .


R e s u l t s And

Discussion of F i n a l

Case

T a b l e s IV-VI p r e s e n t t h e main r e s u l t s c a r r i e d o u t w i t h 1, 3 and 10 p l e n u m s . d i v i d e d i n two c a t e g o r i e s : (i)

(ii)

of the s i m u l a t i o n s Most c a s e s c a n be

the f i r e i s v e r y i n t e n s e but runs out and s e l f - e x t i n g u i s h e s f a i r l y q u i c k l y ;

of

oxygen

the f i r e continues burning f o r a long time, p l e n u m t e m p e r a t u r e s a r e f a i r l y low.

but

A number o f a d d i t i o n a l c a s e s were a l s o t r i e d , i n w h i c h t h e r e was a d i r e c t o p e n i n g between t h e p l e n u m and the surroundings. None o f them p r o d u c e d any s i g n i f i c a n t amount o f smoke f l o w i n g i n t o t h e room: t h e n e t flow t h r o u g h t h e o p e n i n g was a l w a y s o u t w a r d , s o t h a t no a i r e n t e r e d t h e system t o r e p l e n i s h t h e oxygen. These cases are not being r e p o r t e d i n d e t a i l here, i n the i n t e r e s t of s p a c e economy. Only those f i r e s i n category ( i ) cause s u f f i c i e n t l y h i g h plenum t e m p e r a t u r e s t o a l l o w d e c o m p o s i t i o n o f t h e PVC. PVC w i l l s t a r t d e c o m p o s i n g a t c a . 473 K, and w i l l decompose r a p i d l y a t t e m p e r a t u r e s a b o v e 523 Κ o n l y . In a l l t h e c a s e s s t u d i e d w i t h t e n plenums, which represent a heating, v e n t i l a t i n g and a i r conditioning s y s t e m , t h e f i r e was of category ( i i ) . Even i n t h o s e c a s e s were t h e u p p e r l e v e l plenum t e m p e r a t u r e e x c e e d e d 523 K, t h i s n e v e r o c c u r r e d f o r a p e r i o d o f more t h a n 2 min. Virtually a l l the fires resulted in a CO concentration in the room upper level which was s u f f i c i e n t l y h i g h t o cause s e r i o u s concern. However, i n a l l s i n g l e plenum c a s e s , t h e s i z e o f t h e l o w e r l e v e l ( c o l d l a y e r ) i n t h e room and i t s CO c o n c e n t r a t i o n s were s u c h t h a t e s c a p e was v i r t u a l l y a l w a y s p o s s i b l e . A t o t a l o f c a . 60 s i m u l a t i o n s were r u n and i n t h e vast majority of them PVC decomposition plays a negligible, i f any, role. I n o n l y two o f t h e single plenum s i m u l a t i o n s was there a high enough plenum temperature f o r PVC d e c o m p o s i t i o n t o t a k e p l a c e o v e r a p e r i o d o f more t h a n 1 min. T h o s e w o r s t c a s e s , v i z . # 2, and # 13, were a n a l y s e d f u r t h e r , by c o n s i d e r i n g v a r i o u s r a t e s o f PVC d e c o m p o s i t i o n (HC1 g e n e r a t i o n ) , d e p e n d i n g on upper l e v e l temperatures.


605

606

FIRE AND POLYMERS T a b l e IV.

Sim.


# 1 (1) 2 (1) 3 (1) 4 (2) 5 (1) 6 (1) 7 (1) 8 (1) 9 (2) 10 (2) 11 (2) 12 (1) 13 (1) 14 (2) 15 (2)

Simulations with a single

Timel >473K min

Time2 >523K min

1

0

plenum

D e p t h maxRm CO maxRm Τ max i n room ppm Κ m 1.7

(11)11,280

(11)

33 8

2

1 (614)

1.8

(11)

4,987

(11)

33 4

1

1 (621)

1.1

(11)

6,150

(11)

34 6

0.9

( 6)12,150 ( 8) 3 0 1

0

0

1

1 (618)

1.1

(10)

6, 121 (11)

34 1

1

1 (622)

1.2

( 9)10,960 (11)

34 4

1

1 (618)

1.2

(11)

2,297

(11)

34 2

1

1 (573)

1.3

(10)

4,808

(11)

34 9

0

0

0.9

( 7) 1,849

( 9) 3 0 3

0

0

1.8

(11)

5,724

( 8) 3 0 0

0

0

1.2

(8) 1,837

( 9) 3 0 4

1

1 (630)

1.6

(11)

6,983

(11)

34 6

2

1 (563)

1.9

(11)

4, 101 (11)

33 5

0

0

1.0

( 7) 1,122

( 9) 3 0 3

0

0

1.4

(10)

3,846

( 8) 3 0 3

Legends: T i m e l : p e r i o d u p p e r l e v e l plenum temperature e x c e e d s 473 K; Time2 : idem f o r 523 Κ (maximum, i n K) ; D e p t h max: maximum smoke l a y e r d e p t h ( t i m e r e a c h e d , i n min) ; Rm CO max: maximum room u p p e r l e v e l [CO] ( t i m e r e a c h e d , i n min) ; Rm Τ max: maximum room u p p e r level temperature (time reached, i n min).

The d e h y d r o c h l o r i n a t i o n r a t e s o f PVC c o n s i d e r e d were [3, 2 9 ] : (a) f o r t h e r a n g e (b) f o r t h e r a n g e (c) f o r t h e r a n g e

473 - 523 K: 0.3 %/min 523 - 563 K: 1.0 %/min above 563 K: 2.3 %/min

Furthermore, f o r lower l e v e l temperatures w e l l below mininum PVC d e c o m p o s i t i o n t e m p e r a t u r e , i t was assumed t h a t no more t h a n 20 % o f t h e c a b l e l e n g t h , v i z . 80 m, was


34.

T a b l e V. Sim.

#


Effect ofPolyvinyl chloride) Wire Coating


1 (1) 2 (1) 3 (1) 4 (2) 5 (1) 6 (1) 7 (1) 8 (1) 9 (2) 10 (2) 11 (2) 12 (1) 13 (1) 14 (2) 15 (2)

Timel >473K min

S i m u l a t i o n s w i t h t h r e e plenums Time2 >523K min

D e p t h maxRm CO maxRm Τ max i n room ppm m Κ

2

2 (541)

1.6

( 2)15,470

(11)

36 4

2

1 (614)

1.8

(11)

4,987

(11)

33 4

1

1 (621)

1.1

(11)

6,150

(11)

3 46

0.9

( 6)12,150

0

0

( 8) 3 0 1

1

1 (618)

1.1

(10)

6,121

(11)

341

1

1 (622)

1.2

( 9)10,960

(11)

34 4

1

1 (618)

1.2

(11)

2,297

(11)

34 2

1

1 (573)

1.3

(10)

4,808

(11)

34 9

0

0

0.9

( 7) 1,849

( 9) 3 0 3

0

0

1.8

(11)

5,724

( 8) 3 0 0

0

0

1.2

(8)

1,837

( 9) 3 0 4

1

1 (630)

1.6

(11)

6,983

(11)

3 46

2

1 (563)

1.9

(11)

4,101

(11)

33 5

0

0

1.0

( 7) 1,122

( 9) 3 0 3

0

0

1.4

(10)

3,846

( 8) 3 0 3

Legends as i n T a b l e IV. decomposed s i m u l t a n e o u s l y . The l i n e a r d e n s i t y o f c a b l e c o a t i n g u s e d i s 70 g/m. In both of these s i m u l a t i o n s , w o r s t c a s e s c e n a r i o s , ( T a b l e V I I ) i t i s c l e a r t h a t t h e HC1 c o n c e n t r a t i o n d o e s n o t i n t r o d u c e much a d d i t i o n a l h a z a r d t o t h a t due t o t h e f i r e i t s e l f , s i n c e t h e l e t h a l p o t e n c i e s o f HC1 a n d o f CO a r e v e r y s i m i l a r [ 1 , 11, 13, 34, 3 5 ] . An investigation of those cases, among the 3 plenum s i m u l a t i o n s , w i t h t h e h i g h e s t p o t e n t i a l f o r e f f e c t s b y PVC y i e l d s t h e same i m p l i c a t i o n s . The main reason for this i s that the products c o n c e r n e d h a v e good f i r e p e r f o r m a n c e . T h e y h a v e v e r y low h e a t r e l e a s e c h a r a c t e r i s t i c s , s o t h a t t h e y do n o t a d d s i g n i f i c a n t l y t o t h e energy o f t h e f i r e and, f u r t h e r m o r e , w i l l n o t s p r e a d f l a m e i n t h e a b s e n c e o f an e x t e r n a l e n e r g y source, so t h a t they h a r d l y i n c r e a s e t h e f u e l supply f o r the f i r e .


607

608

FIRE AND POLYMERS

Sim.

# —

Table VI.

Simulations with

Timel >473K min

Time2 >523K min

t e n plenums

D e p t h maxRm CO maxRm Τ max i n room


m 1 (4) 2 (1) 3 (1) 4 (2) 5 (1) 6 (1) 7 (1) 8 (1) 9 (2) 10 (2) 11 (2) 12 (1) 13 (1) 14 (2) 15 (2)

Κ

ppm

0

0

2.1

( 4)15,050

( 8) 3 3 6

0

0

1.8

(11) 4,987

(11)

33 4

0

0

1.1

(11) 6, 150 (11)

34 6

0

0

0.9

( 6)12,150

( 8) 3 0 1

0

0

1.1

(10) 6,121

(11)

34 1

0

0

1.2

( 9)10,960

(11)

34 4

0

0

1.2

(11) 2,297

(11)

34 2

0

0

1.3

(10) 4,808

(11)

34 9

0

0

0.9

( 7) 1,849

( 9) 3 0 3

0

0

1.8

(11) 5,724

( 8) 3 0 0

0

0

1.2

1,837

( 9) 3 0 4

0

0

1.6

(11) 6,983

(11)

34 6

0

0

1.9

(11) 4,101

(11)

33 5

0

0

1.0

( 7 ) 1, 122 ( 9 ) 3 0 3

0

0

1.4

(10) 3,846

(8)

( 8) 3 0 3

Legends as i n T a b l e IV. Table VII. Simulation

#

R e s u l t s o f Some S i m u l a t i o n s w i t h PVC T/2 Γ7Ϊ3 372 Room Upper L a y e r R e s u l t s

CO § 2 m i n (ppm) 4 , 325 HC1 @ 2 m i n (ppm) 20 CO @ 5 m i n (ppm) 4 , 325 HC1 @ 5 m i n (ppm) 20 CO @ 10 m i n (ppm) 4 ,564 HC1 § 10 m i n (ppm) 202 Max Temp (K) 335 Max Smoke l a y e r (m)

3,13

1, 221 0 1, 593 108 3, 828 668 335 1.8

3, 314 0 5, 204 112 5, 204 112 327 1.9

2 , 957 93 3, 156 126 5, 282 696 353 2.0

562

497

583

9 9

Max P l e n Temp (K)

615


34.




Conclusions F i r e s s t a r t i n g i n a room may e v e n t u a l l y g e t t r a n s f e r r e d t o a p l e n u m a b o v e i t . However, by t h e t i m e t h e e f f e c t s o f such a fire cause PVC products (rigid c o n d u i t , ENMT c o n d u i t and w i r e c o a t i n g ) i n t h e plenum t o b u r n , t h e room has a l r e a d y r e a c h e d f l a s h o v e r c o n d i t i o n s . Furthermore, t h e smoke g e n e r a t e d by t h e room f i r e f u e l c a u s e s much f a s t e r t o x i c c o n c e r n t h a n t h a t f r o m t h e PVC p r o d u c t s i n t h e plenum. Fires starting i n a plenum communicated to the o u t s i d e are u n l i k e l y t o cause concern i n h a b i t a b l e areas. If the plenum i s isolated from the o u t s i d e , a fire starting i n i t i s more l i k e l y t o cause a hazardous s i t u a t i o n i n t h e room b e l o w i f t h e p l e n u m i s c o m m u n i c a t e d w i t h o t h e r plenums. The u s e o f f i r e s a f e PVC w i r e c o a t i n g p r o d u c t s i n a plenum, d i d n o t c o n t r i b u t e , in virtually any of the s i m u l a t i o n s r e p o r t e d here, to a s i g n i f i c a n t i n c r e a s e i n t h e f i r e h a z a r d due t o t h e f i r e i t s e l f . This conclusion i s v a l i d b o t h f o r t h e c a s e s where t h e f i r e s t a r t s i n t h e room and f o r t h e c a s e s where t h e f i r e starts i n the plenum.

References 1. 2. 3. 4. 5.

6. 7.

8.

H i r s c h l e r , M.M. General P r i n c i p l e s of F i r e Hazard and the Role of Smoke T o x i c i t y , T h i s volume. C u l l i s , C.F. and H i r s c h l e r , M.M. The Combustion of Organic Polymers, Oxford U n i v e r s i t y Press, Oxford, 1981. H i r s c h l e r , M.M., Europ. Polvmer J., 22, 153 (1986). H i r s c h l e r , M.M., F i r e Prev. 204, November, p. 19 (1987). Smith, Ε.Ε.,in Ignition, Heat Release and Non-combustibility of M a t e r i a l s , A.S.T.M. STP 502 (Ed. A.F. Robertson), p.119, Amer. Soc. T e s t i n g Mater., P h i l a d e l p h i a , PA (1972). H i l a d o , C.J., Flammability Handbook f o r P l a s t i c s . 3rd.Edn, Technomic, Lancaster, 1982. H i r s c h l e r , M.M. and Smith, G.F. Determination of F i r e P r o p e r t i e s of Products by Rate of Heat Release C a l o r i m e t r y : Use of the N a t i o n a l Bureau of Standards Cone and Ohio State U n i v e r s i t y Instruments, i n Proc. F i r e Retardant Chemicals Assoc. Fall 1987 Conf., F i r e Safety Progress i n Regulations, Technology and New Products, Monterey, CA, Oct. 18-21, p.133 (1987). H i r s c h l e r , M.M. and Smith, G.F., Eastern States Comb. I n s t . F a l l Tech. Mtg, Nov. 2-6, 1987, pap. 63, Gaithersburg, MD, Combustion I n s t i t u t e , P i t t s b u r g h , PA (1987).


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22.

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November 1, 1989


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