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Evaluation of the effectiveness of fire stops in preventing fire spread in
concealed spaces
EVALUATION OF THE EFFECTIVENESS OF FIRE STOPS I N PREVENTING FIRE SPREAD I N CONCEALED SPACES
by W. T a y l o r PREFACE T h i s r e p o r t d e s c r i b e s a series of t e s t s c a r r i e d o u t t o e v a l u a t e t h e e f f e c t i v e n e s s of some f i r e - s t o p m a t e r i a l s i n p r e v e n t i n g t h e e x c e s s i v e movement of f i r e w i t h i n a c o n c e a l e d s p a c e l i n e d w i t h expanded p o l y s t y r e n e i n s u l a t i o n . The tests d e m o n s t r a t e d t h e s a t i s f a c t o r y p e r f o r m a n c e o f a s b e s t o s b o a r d s t o p s and s h e e t metal s t o p s i n c o n t r o l l i n g f i r e movement, b u t some d o u b t r e m a i n s a b o u t t h e t o t a l e f f e c t i v e n e s s o f wood s t o p s .
The i n v e s t i g a t i o n w a s p a r t of a program examining t h e f i r e b e h a v i o u r of foamed p l a s t i c s used a s b u i l d i n g i n s u l a t i o n . The program w a s s p o n s o r e d j o i n t l y by t h e S o c i e t y of t h e P l a s t i c s I n d u s t r y of Canada and t h e N a t i o n a l R e s e a r c h C o u n c i l of Canada. The a u t h o r , D r . W i l l i a m T a y l o r , h e l d t h e p o s i t i o n of DBR P l a s t i c s R e s e a r c h F e l l o w from 1979 t o 1981. O t h e r r e p o r t s p r e p a r e d by D r . T a y l o r d u r i n g h i s s t a y w i t h t h e D i v i s i o n a r e : - E v a l u a t i o n of t h e r m a l b a r r i e r s f o r foam p l a s t i c s i n s u l a t i o n ( I n t e r n a l R e p o r t No. 466)
-
S p r e a d of f i r e i n v e r t i c a l c o n c e a l e d s p a c e s c o n t a i n i n g f o a m e d - p l a s t i c s i n s u l a t i o n : P a r t I . P o l y u r e t h a n e s and p o l y i s o c y a n u r a t e s ( I n t e r n a l R e p o r t No. 468) P a r t 11. Expanded p o l y s t y r e n e s ( I n t e r n a l R e p o r t No. 469)-
S p r e a d o f f i r e i n r e s i d e n t i a l - t y p e wood-frame c o n s t r u c t i o n ( I n t e r n a l R e p o r t No. 471) The D i v i s i o n of B u i l d i n g R e s e a r c h g r e a t l y a p p r e c i a t e s t h e i n t e r e s t and s u p p o r t of t h e S o c i e t y of t h e P l a s t i c s I n d u s t r y i n t h i s program. Ottawa November 1 9 8 1 C . B . Crawford D i r e c t o r DBR/NRCNATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEARCH
OBR INTERNAL REPORT NO. 470
EVALUATION OF THE EFFECTIVENESS OF FIRE STOPS
IN PREVENTING FIRE SPREAD IN CONCEALED SPACES
by W . T a y l o r
Checked by: T
.
Z.
H. Approved by: L.
W.
G.
Date: November 1981 Prepared for: Record p u r p o s e sOne of t h e b a s i c o b j e c t i v e s of f i r e s t o p s ( o r f i r e b a r r i e r s ) s p e c i f i e d i n model b u i l d i n g codes i s t o p r e v e n t u n d e t e c t e d s p r e a d o f f i r e w i t h i n c o n c e a l e d s p a c e s n e a r t h e e x t e r i o r s u r f a c e s of b u i l d i n g s . The f i r e s t o p i s r e q u i r e d t o l e s s e n t h e l i k e l i h o o d o f f i r e e n t e r i n g a concealed s p a c e i f t h e m a t e r i a l l i n i n g t h e s p a c e i s c o m b u s t i b l e o r , i f t h e f i r e h a s p e n e t r a t e d t h e s p a c e , t o p r e v e n t e x c e s s i v e s p r e a d o f f i r e . The p r o p a g a t i o n o f f i r e i n concealed s p a c e s t h a t c o n t a i n c o m b u s t i b l e foamed p l a s t i c i n s u l a t i o n h a s been t h e s u b j e c t of s e v e r a l i n v e s t i g a t i o n s l 9 2 , and v a r i o u s recommendations have been made
c o n c e r n i n g b o t h t h e l i m i t s t h a t should be p l a c e d on t h e f l a n u n a b i l i t y o f t h e i n s u l a t i o n i n t h e c a v i t y and on t h e width of t h e a i r space. L i t t l e work h a s been done t o e v a l u a t e t h e e f f e c t i v e n e s s of t h e f i r e s t o p s p r e s c r i b e d i n t h e N a t i o n a l B u i l d i n g Code o f canadas when t h e recommended c o n d i t i o n s f o r l i m i t i n g t h e s p r e a d o f f i r e i n a c a v i t y w a l l a r e n o t met. Some o f t h e f i r e b a r r i e r m a t e r i a l s approved by t h e Code a p p e a r t o have been s e l e c t e d w i t h wood-frame c o n s t r u c t i o n i n mind and a r e n o t always e f f e c t i v e 3 . The s e r i e s of t e s t s d e s c r i b e d i n t h i s r e p o r t was d e s i g n e d t o e v a l u a t e t h e e f f e c t i v e n e s s o f t h e s e
f i r e - b a r r i e r m a t e r i a l s i n p r e v e n t i n g t h e v e r t i c a l s p r e a d o f a f i r e which h a s p e n e t r a t e d a c a v i t y w a l l l i n e d w i t h expanded p o l y s t y r e n e i n s u l a t i o n .
TEST FACILITY AND PROCEDURE
The t e s t assembly used ( F i g . 1 ) e s s e n t i a l l y comprised a v e r t i c a l
r e c t a n g u l a r d u c t , 5 m h i g h by 1 . 2 5 m wide by 0.115 m d e e p , which was l i n e d on one s i d e w i t h expanded p o l y s t y r e n e i n s u l a t i o n . The i g n i t i o n s o u r c e f o r t h e t e s t s was a n a t u r a l g a s b u r n e r c o n s i s t i n g o f a p i p e , 25 mrn O . D . , w i t h a s e r i e s of 24 r a d i a l h o l e s 4.75 mm i n d i a m e t e r a t 50 mm i n t e r v a l s a l o n g i t s l e n g t h . Gas flow t o t h e b u r n e r was a d j u s t e d t o p r o v i d e a s e r i e s o f f l a m e l e t s w i t h a t o t a l e n e r g y o u t p u t o f 25 kW.
The f i r e s t o p s t o b e t e s t e d were i n s t a l l e d a t t h e m i d - h e i g h t of t h e assembly i n t h r e e d i f f e r e n t a r r a n g e m e n t s a s shown s c h e m a t i c a l l y i n F i g . 2. With a r r a n g e m e n t s A and B , f u l l v e n t i l a t i o n and d r a i n a g e o f t h e c a v i t y was a l l o w e d by means o f 25 mm s l o t s above and below t h e f i r e s t o p . I n A , t h e s t o p p r o j e c t e d 75 mm i n f r o n t o f t h e assembly f a c e ; i n B i t ended f l u s h w i t h t h e f r o n t f a c e . In arrangement C , t h e f i r e s t o p p r o v i d e d a complete c l o s u r e a c r o s s t h e a i r s p a c e , t h u s l i m i t i n g v e n t i l a t i o n b u t n o t d r a i n a g e o f t h e c a v i t y . I n e v a l u a t i n g t h e e f f e c t i v e n e s s o f f i r e s t o p s , a c o n f i g u r a t i o n was r e q u i r e d by which t h e p e r f o r m a n c e o f t h e b a r r i e r , r a t h e r t h a n t h a t o f t h e foam i n s u l a t i o n , would be d e t e r m i n e d . Based on r e s u l t s o b t a i n e d i n t e s t s w i t h a s i m i l a r p o l y s t y r e n e - l i n e d , unstopped c a v i t y s u b j e c t e d t o t h e same i g n i t i o n s o u r c e 4 , t h e c o n f i g u r a t i o n chosen f o r t h i s s e r i e s o f t e s t s i n v o l v e d a n a i r s p a c e 38 mm i n w i d t h , w i t h t h e i g n i t i o n s o u r c e i n t r o d u c e d i n t o t h e c a v i t y v i a a 25 rnm s l o t i n t h e f r o n t f a c e i m m e d i a t e l y above t h e lower h o r i z o n t a l boundary o f t h e a s s e m b l y . With t h i s arrangement s e v e r e f i r e c o n d i t i o n s d e v e l o p e d d u r i n g t h e t e s t and v i r t u a l l y a l l o f t h e i n s u l a t i o n i n t h e c a v i t y was d e s t r o y e d .
TEST MATERIALS
The i n s u l a t i o n m a t e r i a l used t o l i n e t h e t e s t c a v i t y was a r i g i d , c l o s e d - c e l l p o l y s t y r e n e foam w i t h a d e n s i t y o f 32 kg/m3, m a n u f a c t u r e d by t h e
e x t r u s i o n p r o c e s s , i n t h e form o f b o a r d s 2400 mm long by 600 mm wide by 75 mm t h i c k .
T h r e e f i r e - s t o p m a t e r i a l s t h a t a r e l i s t e d i n t h e N a t i o n a l B u i l d i n g c o d e 5 a s s a t i s f a c t o r y were used i n t h e t e s t s : 1 2 . 5 mm a s b e s t o s cement b o a r d ,
18 gauge s h e e t s t e e l and 38 mm s o l i d lumber. TEST RESULTS
1 . Arrangements A and B
The r e s u l t s were g e n e r a l l y s i m i l a r f o r each o f t h e f i r e - s t o p m a t e r i a l s t e s t e d w i t h t h e c a v i t y f u l l y v e n t i l a t e d . I n i t i a l l y , h e a t from t h e s o u r c e b u r n e r c a u s e d m e l t i n g o f t h e expanded p o l y s t y r e n e i n t h e lower p a r t o f t h e
c a v i t y . The melted m a t e r i a l flowed down t h e c a v i t y w a l l s and accumulated on t h e h o r i z o n t a l b a s e of t h e assembly where it was e v e n t u a l l y i g n i t e d by t h e s o u r c e b u r n e r f l a m e s . The a d d i t i o n a l h e a t from t h i s burning m a t e r i a l melted more p o l y s t y r e n e h i g h e r i n t h e c a v i t y which t h e r e b y added f u e l t o t h e f i r e and i n c r e a s e d i t s s i z e . F i n a l l y i g n i t i o n of a l l m a t e r i a l remaining i n t h e c a v i t y o c c u r r e d and a s t r e a m of b u r n i n g polymer poured down t h e w a l l s t o t h e b a s e and o u t o n t o t h e f l o o r o f t h e t e s t a r e a where i t c o n t i n u e d t o burn i n a pool around t h e b a s e o f t h e t e s t assembly. Flames from t h e b u r n i n g foam
i n s i d e t h e c a v i t y were momentarily v i s i b l e a t t h e v e n t i l a t i o n s l o t below t h e f i r e b a r r i e r , b u t appeared t o r e c e d e a s t h e b u r n i n g p o l y s t y r e n e flowed o u t o f t h e c a v i t y . Heavy b l a c k smoke evolved from t h e burning m a t e r i a l .
Examinations f o l l o w i l ~ g th e completion of each t e s t r e v e a l e d t h a t , i n a l l c a s e s , a l l t h e expanded p o l y s t y r e n e below t h e f i r e b a r r i e r had been consumed, and o n l y a heavy d e p o s i t o f s o o t had been l e f t on t h e i n n e r w a l l s . Above t h e f i r e s t o p , r e g a r d l e s s of whether o r n o t i t p r o j e c t e d i n f r o n t o f t h e assembly f a c e , t h e o n l y e f f e c t on t h e i n s u l a t i o n was a s m a l l amount of s u r f a c e m e l t i n g and s h r i n k a g e c l o s e t o t h e b a r r i e r ( F i g . 3 ) . T h i s e f f e c t was g r e a t e s t i n t h e c a s e o f t h e s h e e t s t e e l b a r r i e r .
The c o n d i t i o n of t h e f i r e b a r r i e r s was g e n e r a l l y good f o l l o w i n g t h e t e s t , a l t h o u g h t h e s h e e t s t e e l b a r r i e r was s l i g h t l y warped and t h e wood s t o p was s l i g h t l y c h a r r e d on i t s lower s u r f a c e .
The s u c c e s s o f t h e wooden f i r e s t o p i n p r e v e n t i n g t h e f i r e from s p r e a d i n g i n t o t h e upper s e c t i o n of t h e t e s t assembly was p r o b a b l y due t o t h e r a p i d downward movement o f burning m a t e r i a l , once i g n i t i o n of expanded p o l y s t y r e n e i n s i d e t h e c a v i t y took p l a c e . Thus, a l t h o u g h flames were s e e n t o r e a c h t h e f i r e s t o p d u r i n g t h e t e s t , t h e time d u r i n g which t h e y c o n t a c t e d t h e wood was v e r y s h o r t and caused o n l y s u p e r f i c i a l c h a r r i n g .
2 . Arrangement C
Only a s b e s t o s board and s h e e t s t e e l f i r e s t o p s were t e s t e d i n t h i s c o n f i g u r a t i o n .
Without t h e v e n t i l a t i o n of t h e c a v i t y , somewhat l e s s s e v e r e f i r e
c o n d i t i o n s developed. The expanded p o l y s t y r e n e m e l t e d more s l o w l y and t h u s d e l a y e d t h e development of f i r e a t t h e b a s e o f t h e t e s t assembly. The pool f i r e s which e v e n t u a l l y developed on t h e f l o o r around t h e b a s e o f t h e
assembly were a l s o l e s s s e v e r e t h a n w i t h arrangements A and B.
A t t h e completion o f t h e t e s t s , i t was a g a i n found t h a t a l l t h e i n s u l a t i o n i n t h e lower c a v i t y had been consumed, b u t t h a t above t h e f i r e s t o p t h e foam was u n a f f e c t e d a p a r t from a l i m i t e d amount o f s u r f a c e m e l t i n g and s h r i n k a g e immediately above t h e s t o p .
CONCLUSlONS
The t e s t r e s u l t s i n d i c a t e t h a t i n a n assembly l i n e d w i t h expanded p o l y s t y r e n e , i n which t h e c o n d i t i o n s a r e such t h a t r a p i d s p r e a d o f f i r e
w i t h i n a c o n c e a l e d s p a c e i s p o s s i b l e , t h e u s e of f i r e s t o p s o f a s b e s t o s cement board o r s h e e t s t e e l , a s p r e s c r i b e d by t h e N a t i o n a l B u i l d i n g Code, i s a n e f f e c t i v e means o f c o n f i n i n g t h e f i r e t o t h e c a v i t y o f o r i g i n . Although l e s s s e v e r e f i r e c o n d i t i o n s developed w i t h a c o n f i g u r a t i o n t h a t p e r m i t t e d d r a i n a g e b u t n o t v e n t i l a t i o n o f t h e s p a c e (arrangement C), t h e f i n a l r e s u l t was t h e same f o r a l l t h r e e f i r e - s t o p c o n f i g u r a t i o n s e v a l u a t e d . I n t h e s e t e s t s t h e wooden f i r e s t o p . w a s a l s o s u c c e s s f u l i n p r e v e n t i n g upward s p r e a d o f f i r e , due t o t h e tendency o f burning p o l y s t y r e n e t o f l o w down t h e c a v i t y and away from t h e s t o p b e f o r e t h e f l a m e s i g n i t e d t h e wood. I n o t h e r s i t u a t i o n s , however, t h e performance o f wooden f i r e s t o p s may n o t be s a t i s f a c - t o r y . For example, a v e r t i c a l b a r r i e r i n t e n d e d t o l i m i t h o r i z o n t a l s p r e a d o f f i r e o r a h o r i z o n t a l b a r r i e r below t h e p o i n t o f f i r e o r i g i n would be v u l n e r a b l e t o i g n i t i o n by burning polymer flowing t o t h e bottom o f t h e c a v i t y . For t h i s r e a s o n t h e u s e o f wood a s a f i r e s t o p i n s p a c e s l i n e d w i t h expanded p o l y s t y r e n e i s n o t recommended.
REFERENCES
1. L i e , T.T. C o n t r i b u t i o n o f i n s u l a t i o n i n c a v i t y w a l l s t o p r o p a g a t i o n of f i r e . Nat. Res. Council Canada, Div. Bldg. R e s . , F i r e Study No. 29,
(NRCC 1 2 8 7 8 ) , Ottawa, Nov. 1972.
2 . D'Souza, M . V . F i r e p r o p a g a t i o n t e s t s w i t h foamed p l a s t i c s i n s u l a t i o n w i t h i n a c a v i t y w a l l . Nat. Res. Council Canada, Div. Bldg. Res., Ottawa, DBR I n t e r n a l Report No. 424, Ottawa, Feb. 1976
3 . T a y l o r , W. Spread o f f i r e i n v e r t i c a l concealed s p a c e s c o n t a i n i n g
f o a m e d - p l a s t i c s i n s u l a t i o n , P a r t I . Nat. Res. Council Canada, Div. Bldg. Kes., DBR I n t e r n a l Report No. 471, Ottawa.
4 . T a y l o r , W. Spread o f f i r e i n v e r t i c a l c o n c e a l e d s p a c e s c o n t a i n i n g
f o a m e d - p l a s t i c s i n s u l a t i o n , P a r t 11. Nat. Res. Council Canada, Div. Bldg. R e s . , DBR I n t e r n a l Report No. 469, Ottawa.
5 . N a t i o n a l B u i l d i n g Code o f Canada 1980, S u b s e c t i o n 3.1.9. Nat. Res. C o u n c i l Canada Assoc. Comm, on t h e N . B . C . , (NRCC 17303), Ottawa.
: . I L----' F L A M E S O U R C E
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A I R S P A C E I N F R O N T O F I N S U L A T I O N F I G U R E 1 C A V I T Y W A L L T E S T R I GI N S U L A T I O N
F l R E S T O P
I N S U L A T I O N
l a ) FULL VEN'TI LATIOIV, (b) FULL VENTILA'fION, FLILL D R A I NAGE FULL DRAINAGE
75 rnrn PROJECTION OF STOP NO PROJECTION OF STOP
(c) N O VEIV'~ILATION, FULL DRA INAGE
F I G U R E 2
A R R A N G E M E N T S F O R F I R E S T O P P I I V G O F V E R T I C A L F L A M E S P R E A D
Figure 3
