Soot fires in chimneys and smokepipes in Ottawa houses, 1956-57

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NATIONAL RESEARCH COUNCIL OF CANADA D I V I S I O N OF BUILDING

RESEARCH

SOOT F I R E S I N CHIMNEYS

AND

SMOKEPIPES

I N OTTAWA HOUSES,

1956-57

Report No.

170

of the

D i v i s i o n

of

B u i l d i n g

Researoh

O t t a w a Maroh

1959

PREFACE

The D i v i s i o n has been p r i v i l e g e d t o have t h e f u l 1 oo-operation of t h e Ottawa F i r e Department i n any f i r e s t u d i e s o a r r i e d out i n t h e Ottawa

a r e a . When

i t

was d e s i r e d , a s p a r t of a study of ohimneys, t o examine i n d e t a i l oases of ohimney f i r e s t h e Department arranged n o t only t o provide information on chimney f i r e s i n Ottawa a s t h e y ocourred, but a l s o a s s i s t e d

i n

the subsequent f i e l d v i s i t s . The r e s u l t s of f i e l d o b s e r v a t i o n s , t o g e t h e r with information obtained from l a b o r a t o r y examination of t y p i c a l ohimney d e p o s i t s a r e now r e p o r t e d .

The a u t h o r was formerly a Researoh O f f i o e r w i t h the Building S e r v i c e s S e o t i o n and i s now t a k i n g post graduate s t u d i e s a t t h e Rensselaer Polytechnio I n s t i t u t e i n Troy, N.Y.

Ottawa

SOOT FIRES I N CHIMNEYS

AND

SMOKEPIPES

I N O!M'AWA HOUSES, 1956-57

Many house f i r e a i n Canada o r i g i n a t e from soot f i r e s i n chimneys and smokepipes. F i r e s t a t i s t i c s published a n n u a l l y by p r o v i n c i a l f i r e marshals g i v e t h e number of suoh f i r e a

and l o s s e s r e s u l t i n g from them but do n o t i n d i o a t e s t r u c t u r a l d e t a i l s of houses, chimneys, and h e a t i n g systems.

High m a t e r i a l temperatures and severe thermal s t r e s s e s i n masonry chimneys a r e caused by burning soot. I n s e v e r a l c o u n t r l e s temperatures i n chimneys d u r i n g such f i r e s have

been measured and t h e performance of t h e chimney w a l l s has been studied.

Chimneys and smokepipes could be b u i l t t o w i t h s t a n d s a f e l y soot f i r e temperatures i f c o n s t r u c t e d s p e c i f i c a l l y f o r such operation. Such construc t i o n f o r masonry domestic3 chimneys has not been considered r a t i o n a l , because of high c o s t and

aoceptanoe of r i s k of a soot f i r e , I n f a o t , f r e q u e n t l y t o lower c o s t , q u a l i t y of c o n s t r u c t i o n h a s a l s o been lowered, To ensure t h a t ohimneys and smokepipes a r e b u i l t t o conform a t l e a s t t o minimum s t a n d a r d s of f i r e s a f e t y , s p e c i f i c r e g u l a t i o n s have been

drawn up and included i n b u i l d i n g oodes which b u i l d e r s a r e r e q u i r e d t o observe. I n some i n s t a n c e s , however, no such r e g u l a t i o n s have been observed.

The purpose of t h e i n v e s t i g a t i o n desoribed here was t o de terming t

1. The n a t u r e of soot d e p o s i t e d i n chimneys and smokepipe a

.

2. The t y p e s of chimneys and smokepipes involved i n soot f i r e s .

3.

What f u e l s and h e a t i n g systems were a s s o c i a t e d w i t h soot f i r e a .

4.

The i n f l u e n c e of o u t s i d e ambient temperature on h e a t i n g syatem o p e r a t i o n l e a d i n g t o s o o t f i r e s .

5.

_{I f soot f i r e s i n chimneys and smokepipes were}

Chimney D e p o s i t s The g e n e r a l r e q u i r e m e n t s f o r p r o p e r i g n i t i o n and combustion of f u e l s c a n be summarized a s f o l l o w s : 1, a d e q u a t e s u p p l y of a i r i n i n t i m a t e c o n t a a t w i t h c o m b u s t i b l e f u e l components, 2. a d e q u a t e t e m p e r a t u r e s i n t h e combustion chamber above f u e l i g n i t i o n p o i n t . These c o n d i t i o n s a r e f r e q u e n t l y n o t f u l f i l l e d i n d o m e s t i c h e a t i n g u n i t s . P r o p e r a d m i s s i o n and m i x i n g of a i r and a d e q u a t e tempera-

t u r e s a r e d i f f i c u l t t o m a i n t a i n a t a l l t i m e s u n d e r d i f f e r e n t c o n d i t i o n s o f h e a t i n g - u n i t o p e r a t i o n , p a r t i c u l a r l y w i t h s o l i d f u e l burned on g r a t e s and o i l burned i n v a p o r i z i n g b u r n e r s . If p r o p e r combustion does n o t t a k e p l a c e , u n b u r n t f u e l components may be c a r r i e d i n t o t h e smokepipe and chimney w i t h f l u e g a s and f o r m c o m b u s t i b l e d e p o s i t s .

To o b t a i n i n f o r m a t i o n on t h e s e d e p o s i t s , samples from

s o l i d - f u e l and o i l - f i r e d d o m e s t i c h e a t i n g u n i t s were examined. D e t a i l s a r e g i v e n i n T a b l e s I t o I V . T a b l e I g i v e s g e n e r a l i n f o r m a t i o n on t h e s o o t samples. Wood f u e l a p p e a r s r e s p o n s i b l e f o r caked-on d e p o s i t s o f t e n w i t h a g l o a s y s u r f a c e , t h e o t h e r s o l i d f u e l s o r c o m b i n a t i o n s of f u e l s g i v e g r a n u l a r d e p o s i t s of v a r y i n g f i n e n e s s , and o i l r e s u l t s i n s o f t amorphous d e p o s i t s . The u l t i m a t e c h e m i c a l a n a l y s i s f o r c a r b o n and hydrogen was o b t a i n e d on s o o t samples ground t o a

powder and d r i e d a t 230°F ( l l O ° C ) .

F l a s h and f i r e p o i n t s of s o o t samples d e t e r m i n e d by C l e v e l a n d open c u p t e s t a r e g i v e n i n Table 11. Although a l l samples a p p e a r e d c o m b u s t i b l e o n l y numbers 2 a n d

3

burned w i t h a v i s i b l e f l a m e . The t e m p e r a t u r e v a l u e s g i v e n must be a c c e p t e d a s a p p r o x i m a t e o n l y s i n c e ,

i n

s p i t e of p r e c a u t i o n s , a t e m p e r a t u r e g r a d i e n t e x i s t e d i n t h e sample between cup and thermocouple.

On t h e b a s i s of o t h e r t e s t s t h i s t e m p e r a t u r e d i f f e r e n c e i s e s t i m a t e d a s l e s s t h a n 30°F. Weight l o s s e s on h e a t i n g a n d a s h c o n t e n t a r e g i v e n i n T a b l e 111. The w e i g h t l o s s a s p e r c e n t a g e o f o r i g i n a l w e i g h t d u r i n g i n i t i a l h e a t i n g a t 221°F (10S0C) f o r 2 h o u r s p r i m a r i l y r e p r e s e n t s m o i s t u r e a l t h o u g h a l o s s o f more v o l a t i l e hydro-

c a r b o n s must be assumed. Subsequent h e a t i n g a t 392OF ( 2 0 0 ' ~ ) and 572OF (300°C) g i v e s a n i n d i c a t i o n o f q u a n t i t y o f more

2 and

3

appear t o c o n t a i n more of t h e s e v o l a t i l e s t h a n do t h e o t h e r s ( s e e a l s o Table I ) . Two v a l u e s of r e s i d u e a r e g i v e n a f t e r h e a t i n g t o 1 6 5 ' 2 0 ~ (900°C) and l922OF (10sO0C). The f o r m e r may s t i l l i n c l u d e some carbon, whereas t h e l a t t e r a l r e a d y may have l o s t some of t h e more v o l a t i l e s a l t s . Both t h e s e v a l u e s d i f f e r t o some e x t e n t from the ones g i v e n

i n

Table I; d i f f e r e n c e s i n d e t a i l of t h e samples may be t h e c a u s e , The l a r g e a s h c o n t e n t s of samples

6, 7

and

8

a r e due t o f i n e d e b r i s swept from t h e masonry chimneys from which t h e y were taken.

Table I V g i v e s v a l u e s of a c i d i t y of aqueous s o l u t i o n s of some of t h e s o o t samples and the a l k a l i n i t y of c o r r e s p o n d i n g a s h , The low pH v a l u e s f o r t h e s o o t , p a r t i c u l a r l y f o r samples

5

and

9,

i n d i c a t e p r e s e n c e of a h i g h l y i o n i z i n g a c i d presumably s u l p h u r o u s a c i d ; o r g a n i o a c i d s may a l s o be p r e s e n t . The s o o t , t h e r e f o r e , h a s c o r r o s i v e p r o p o r t i e s .

The a n a l y s i s of s o o t samples o b t a i n e d from chimneys and smokepipe s s e r v i n g wood, c o a l and o i l - f i r e d h e a t i n g u n i t s

s u g g e s t s t h e p r e s e n c e of a h i g h p r o p o r t i o n of v o l a t i l e hydro- c a r b o n s i n f r e e carbon, y 3 ; . t i c u l a r l y i n s o o t t a k e n from a wood-burning u n i t ( s a m p l e s 2 and

3 ) .

Although t h e f u e l

c o n d i t i o n and c o m p o s i t i o n and combustion c o n d i t i o n s c o u l d n o t be a s c e r t a i n e d p r e c i s e l y , t h e informa t i o n a v a i l a b l e p o i n t s t o a p r o c e s s of f r a c t i o n a l d i s t i l l a t i o n of f u e l d u r i n g s u s t a i n e d p e r i o d s of low f i r e w i t h c o n d e n s a t i o n and d e p o s i t i o n of r e a d i l y combustible m a t e r i a l i n t h e oold smokepipe and chimney. Furnace o p e r a t i o n l e a d i n g t o s u c h c o n d i t i o n s i s l i k e l y t o p r e v a i l

d u r i n g mild weather i n s p r i n g and f a l l when l i t t l e house h e a t i n g i s r e q u i r e d and h e a t i n g u n i t s a r e o p e r a t e d a t low f i r e .

A l l s o o t samples a p p e a r e d combustible. I n s t i l l a i r a t e m p e r a t u r e a t which b u r n i n g began could be d e t e r m i n e d f o r samples 2 and

3.

No such c l e a r i n d i c a t i o n was observed w i t h t h e o t h e r samples, I n a slow a i r s t r e a m , however, b u r n i n g was observed w i t h a l l samples above 750°F ( 4 0 0 ~ ~ ) .

O b s e r v a t i o n s i n t h e F i e l d

The s e v e r i t y of t h e r m a l l o a d on a chimney o r smokepipe i s d e t e r m i n e d by t h e b u r n i n g t e m p e r a t u r e and d u r a t i o n of t h e

s o o t f i r e . Temperatures of 1250°F

( 6 7 5 ' ~ )

t o 2200°F ( 1 2 0 5 ~ ~ ) i n masonry chimneys have been r e p o r t e d . H i g h e s t t e m p e r a t u r e s of over 2150°F

( l l 7 s 0 C )

were r e c o r d e d i n Norway, of over 1830°F ( 1 0 0 0 ° ~ )

i n

S w i t z e r l a n d and of over 2000°F (1095'C) i n Germany. Maximum t e m p e r a t u r e s were u s u a l l y a t t a i n e d i n under 1 0 m i n u t e s

and were maintained f o r 1 0 t o

60

m i n u t e s , Temperatures i n upper p a r t s of t h e chimney were f r e q u e n t l y h i g h e r t h a n i n lower s e c t i o n s .

The performance of chimneys and smokepipes under t h e s e c o n d i t i o n s v a r i e d w i t h m a t e r i a l s used. Cracking of masonry w a s a u s u a l consequence, Damage v a r i e d from h a i r l i n e c r a c k s

s u s t a i n e d d u r i n g s h o r t - d u r a t i o n f i r e s t o s e v e r e c r a c k i n g and m a t e r i a l d i s i n t e g r a t i o n d u r i n g extreme-temperature f i r e s of l o n g d u r a t i o n , Some p r o t e c t i o n f o r t h e ohimney m a t e r i a l s was a f f o r d e d by s o o t which s w e l l e d when b u r n i n g and formed a l a y e r of porous i n s u l a t i n g m a t e r i a l over t h e i n s i d e s u r f a c e s of t h e chimney, Temperatures on the o u t s i d e s u r f a c e of t h e chimney depended on t h e i n t e n s i t y and d u r a t i o n of t h e s o o t f i r e and t h e c o n d u c t i v i t y of t h e ohimney m a t e r i a l . Temperatures t o

SOO OF

( 2 7 5 ' ~ ) have been mentioned w i t h t h e maximum being a t t a i n e d some time a f t e r the peak of the s o o t f i r e .

To o b t a i n informa t i o n on t h e background of s o o t f i r e s i n chimneys and smokepipes of Canadian houses a f i e l d s t u d y was c a r r i e d out i n t h e C i t y of Ottawa d u r i n g t h e

1956-1957

h e a t i n g season. Apart from convenience of l o c a t t i o n , housing i n Ottawa o f f e r e d s u f f i c i e n t v a r i a t i o n i n t y p e and q u a l i t y of c o n s t r u c t i o n and v a r i a t i o n i n type of h e a t i n g u n i t s and f u e l s used t o make such a s t u d y r e p r e s e n t a t i v e of u r b a n c o n d i t i o n s

i n Canada.

The f i e l d study c a r r i e d out i n c o - o p e r a t i o n w i t h t h e Ottawa F i r e P r e v e n t i o n Bureau l a s t e d 23 weeks, from November 26,

1956

t o May

5,

1957,

L o c a t i o n s of s o o t f i r e s i n chimneys and smokepipes which had been r e p o r t e d t o t h e C i t y F i r e

Department were v i s i t e d and o b s e r v a t i o n s on house and chimney c o n s t r u c t i o n , type of h e a t i n g system and f u e l used were

t a b u l a t e d . The o b s e r v a t i o n s d i s c u s s e d h e r e i n c l u d e

54

c a s e s of s o o t f i r e s i n chimneys o r smokepipes i n v o l v i n g

81

h e a t i n g u n i t s of which seven l e d t o house f i r e s

( 3

c a u s i n g major

damage), 1 0 i n s t a n c e s of house f i r e s caused by o v e r h e a t i n g from smokepipes (no s o o t f i r e s ) and

5

c a s e s of house f i r e s where poor workmanship i n chimney c o n s t r u c t i o n was r e s p o n s i b l e f o r o v e r h e a t i n g of woodwork d u r i n g normal h e a t ing-system

o p e r a t i o n (no s o o t f i r e s ) . Observations of t h e f i r s t group form the b a s i s of t h i s study.

Table V g i v e s the r e l a t i o n s h i p of t h e number of s o o t f i r e s t o o u t s i d e a i r temperature and house age group. These former v a l u e s a r e a l s o p l o t t e d i n Fig. 1. O b s e r v a t i o n s

i n d i c a t e d t h a t t h e number of s o o t f i r e s i n chimneys and smoke- p i p e s i n o r e a sed a p p r e c i a b l y i n sub-zero weather when house

h e a t i n g r e q u i r e m e n t s were h i g h and c a l l e d f o r i n t e n s i v e h e a t i n g s y s t e m o p e r a t i o n . The

r

m

j o r i t y of s o o t f i r e s o c c u r r e d i n

h o u s e s o v e r 4 0 y e a r s of a g e , most o f which were o n l y o f p o o r t o f a i r c o n s t r u c t i o n . F i f t y - e i g h t p e r c e n t of t h e h o u s e s were b u i l t a s m u l t i p l e - f a m i l y d w e l l i n g s ( a p a r t m e n t s and rooming h o u s e s 2 5 p e r c e n t , row h o u s e s

14

p e r c e n t , d o u b l e s 1 2 p e r c e n t and d u p l e x e s

7

p e r c e n t ) and 42 p e r c e n t were b u i l - t a s s i n g l e s . N i n e t y p e r c e n t of a l l h o u s e s were of wood-frame c o n s t r u c t i o n , t h o r e m a i n i n g 1 0 p e r c e n t b e i n g of s o l i d b r i c k , c i n d e r b l o c k o r r e i n f o r c e d c o n c r e t e . S e v e n t y p e r c e n t of t h e h o u s e s had basements. Almost w i t h o u t e x c e p t i o n the municipa 1 b u i l d i n g by-

law c l e a r a n c e r e q u i r e m e n t s f o r chimneys and smokepipes had n o t b e e n observed. Wood house f r a m i n g , j o i s t s , f l o o r s and trim were f r e q u e n t l y i n c o n t a c t w i t h t h e chimney masonry;

i n

some h o u s e s w a l l p a p e r o r f i b r e b o a r d fcrmed t h e c h i m n e y ' s o u t s i d e f i n i s h .

Table V I g i v e s ohimney d o t a i l s . It i n d i a a t e s t h a t t h e m a j o r i t y of t h e chimneys inspected were of b r i c k masonry

c o n s t r ~ u c t i o n w i t h n o 1 j n e r . q and t h a t

40

p e r c e n t of all chimneys were s u p p o r t e d by wooden s h e l v e s b r a c k e t e d i n t o t h e s t r u c t x r a l f r a m i n g of t h e b u i l d i n g s most of t e n a t u p p e r - s t o r y l e v e l . Only

55

p e r c e n t of a l l chimneys had c l e a n o u t s ; t h e s e were a l m o s t e n t i r e l y r e s t r i c t e d t o chimneys w i t h f o o t i n g s . S o o t r e m o v a l from the b r a c k e t chimneys was p o s s i b l e , t h e r e f o r e , o n l y t h r o u g h t h e t h i m b l e w i t h t h e srrrokepipe removed. F i f t y p e r c e n t of a l l chimneys were u s e d f o r m u l t l . p l e v e n t i n g . The maximum number of h e a t i n g a p p l i a n c e s i n u s e p e r f l u e was f i v e , a l t h o u g h one chimney had s i x t h i m b l e s , f o u r of which were i n u s e . C o v e r s o v e r unused t h i m b l e s were of s h e e t m e t a l . I n some h o u s e s t h e room woodwork o r w a l l p a p e r f orned t h e c o v e r o u t s i d e f i n i s h .

Khere s o o t f i r e s i n chimneys and smokepipes had l e d t o house f i r e s , s u b s t a n d a r d c o n s t r u c t i o n and p o o r c o n d i t i o n of h o u s e s and chimneys were n o t e d . C l e a r a n c e r e q u i r e n i e n t s had n o t b e e n o b s e r v e d . L i n e r s had n o t b e e n f i t t e d i n any of t h e

chimneys. No o t h e r s p e c i f i c c o n s t r u c t i o n f e a t u r e s , however, a p p e a r e d i n d i c a t i v e of s p e c i a l f i r e haza1.d.

Almost a l l snlokepipes were of s h e e t m e t a l and were u n i n s u l a t e d . The m a j o r i t y were between

15

and 20 f e e t l o n g ; however, s e v e n were 30 t o 4.0 f e e t l o n g and s i x ware o v e r 110

f e e t l o n g .

Table V11 g i v e s t h e t y p e of h e a t i n g u n i t s which were a s s o c i a t e d w i t h s o o t f i r e s i n chimneys and smokepipes. U n i t s which u s e d d u c t l n g f o r h e a t d 5 . s t r i b u t i o n t o t a l l e d o n l y 2 3 p e r c e n t , whereas two g r o u p s of h e a t i n g u n i t s e a c h exceeded t h i s t h i s f i g u r e : - c o o k s t o v e s

47

p e r cent, and s p a c e h e a t e r s 26 p e r c e n t

.

Fuels u s e d i t 1 t h e s e h e a t i n g u n j - t s a r e l j s t e d i n Table VIII. Most h e a t i n g u n i t s u s i n g d u c t i n g f o r h e a t d i s t r i b u t i o n were s o l i d f u e l - f i r e d , l e s s t h a n h a l f of t h e s e u n i t s b e i n g a u t o m a t i c a l l y c o n t r o l l e d . ; a l l o i l - f j r e d u n i t s had a u t o m a t i c c o n t r o l s . N i n e t y - f i v e p e r c e n t o f a l l c o o k s t o v e s u s e d o n l y wood a s f u e l , o r u s e d i t i n c ~ m b i n z t ~ i o n w i t h a n t b x e c i t e o r b i t u m i n o u s c o a l ; f i r j n g and c o n t r o l . was by hand, J u s t over h a l f of a l l s p a c e l l e a t e r s used s o l i d f u e l f i r e d by hand, w h i l e

t h e r e m a i n d e r u s e d o i l i n evapornative b u r n e r s ; o n l y manual c o n t r o l s were f i t t e d .

A l l s p a c e h e a t e r s , e x c e p t one wood-burning u n i t , and 50 p e r c e n t of a l l cookst;oves were s e r v e d by f l u e s which a l s o

s e r v e d o t h e r h e a t i n g a p p l i a n c e s , I n some h o u s e s smokepipes of two h e a t i n g u n i t s were combjned i n t o one b e f o r e e n t e r i n g t h e chimney. The l o n g e s t of t h e s e j o i n t smokepipes was 11 f e e t ,

The 1 0 house f i r e s a t t r i b u t e d t o o v e r h e a t i n g f r o m smokepipes o r chimneys when no s o o t f i r e s o c c u r r e d were due t o :

I n s u f f i c i e n t c l e a r a n c e a t t h i m b l e where smokepipe p a s s e d t h r o ~ i g h w a l l s o r f l o o r s

7

I n s u f f i c i e n t c l e a r a n c e f r o m smokepipe t o a d j a c e n t c o n l b u s t i b l e m a t e r i a l 2 I n s u f f i c i e n t c l e a r a n c e from m e t a l c o v e r s o v e r unused t h i m b l e s i n chimneys t o a d j a c e n t c o m b u s t i b l e m a t e r i a l 1 I n t h e

5

h o u s e s where f i r e s were a t t r i b u t e d s o l e l y t o p o o r workmanship I.n chimney c o n s t r u c t i o n , b a s i c f i r e - p r o t e c t i o n r e q u i r e m e n t s had n o t been o b s e r v e d ,

I n

one new house, f o r

example, t h e l i n e d b r i c k chimney had o n l y t h r e e masonry w a l l s l e a v i n g t h e b a r e l i n e r i n c o n t a c t w i t h house f r a m i n g a t t h e back.

D i s c u s s i o n of O b s e r v a t i o n s

The n a t u r e of s o o t d e p o s i t e d i n smokepipes and chimneys a p p e a r e d t o depend on:

( i ) t h e f u e l u s e d

( i i ) i n a d e q u a t e a e r a t i o n and low t e m p e r a t u r e s preva i l i n g i n h e a t i n g u n i t combust i o n chambers

( iii ) low i n s i d e s u r f a c e t e m p e r a t u r e s of smoke- p i p e a and chimneys

A n a l y s i s of s o o t s u g g e s t e d t h e p r e s e n c e of a r e l a t i v e l y h i g h p r o p o r t i o n of v o l a t i l e h y d r o c a r b o n s , presunlably be c a u s e of

s u b s t a n t i a l c o n d e n s a t i o n and a d s o r p t i o n by c a r b o n , p a r t i c u l a r l y a t low t e m p e r a t u r e s . I n l a b o r a t o r y t e s t s low i g n i t i o n tempera- t u r e s of s o o t c o u l d be a s s o c i a t e d w i t h h i g h h y d r o c a r b o n c o n t e n t .

The low f i r e p o i n t o b s e r v e d

i n

t h e l a b o r a t o r y , of s o o t from a wood-fired u n i t e x p l a i n s the frequent; r e p o r t t h a t a s o o t f i r e had o c c u r r e d i n what had seemed t o be a c o l d chinlney a f t e r a p e r i o d o f damped-dovm o p e r a t i o n of a wood-burning u n i t d u r i n g a r e l a t i v e l y warm s p e l l , The "low f i r e " o p e r a t i o n of t h e h e a t i n g u n i t had r e s u l t e d i n poor conlbustion and i n c o n s e q u e n t d e p o s i t i o n of r e a d i l y inflammable m a t e r i a l , presumably s i m i l a r t o s a m p l e s 2 and

3,

i n t h e smokepipe and chinmey* A s u b s e q u e n t c a l l f o r

i n c r e a s e d house h e a t i n g would r e s u l t i n nlore i n t e n s i v e h e a t i n g - u n i t o p e r a t i o n and t h u s i n h o t t e r f l u e gas. A s p a r k m i g h t t h e n be enough t o i g n i t e t h e s o o t . Such o p e r a t i o n a p p e a r s t o be common a t t h e end of t h e h e a t i n g s e a s o n w i t h mkld d a y s and c o l d n i g h t s .

C o n d i t i o n s i n t h e f l u e o f a masonry chimney a r e p a r t i c u - l a r l y f a v o u r a b l e t o a soo",ire, The r e l a t i v e i n s u l a t i o n of s o o t and masonry and geometry of t h e s p a c e r e d u c e h e a t l o s s e s t o t h e o u t s i d e , s o t h a t once i g n i t i o n h a s t a k e n p l a c e b u r n i n g i s l i k e l y t o c o n t i n u e . The g a s f l o w t h r o u g h t h e chimney p r o v i d e s s u f f i c i e n t a e r a t i o n of t h e b u r n i n g m a t e r i a l . The p r o c e s s i s cunlula t i v e ; a s t h e chimney t e m p e r a t u r e r i s e s t h e d r a f t i n c r e a s e s c a u s i n g g r e a t e r a i r f l o w t h r o u g h t h e chimney, t h u s promoting more v i g o r o u s b u r n i n g of s o o t and s p r e a d of f i r e t o a d j a c e n t u n i g n i t e d d e p o s i t s . S o o t a c i d i t y d o e s n o t i n f l u e n c e t h e s e v e r i t y of a s o o t f j . r e , a n d a c i d i c c o r r o s i o n of m e t a l smokepipes e v e n w i t h t h e h e a t i n g u n i t ; s h u t down may c a u s e t h e i r weakening and s u b s e q u e n t c o l l a p s e d u r i n g a p e r i o d of t h e r m a l s t r e s s . S m a l l c o o k s t o v e s a n d s p a c e h e a t e r s b u r n i n g s o l i d f u e l ( p a r t i c u l a r l y i f wood) on g r a t e s o r o i l i n e v a p o r a t i v e b u r n e r s formed t h e m a j o r i t y of h e a t i n g u n i t s a s s o c i a t e d w i t h smokepipe and chimney f i r e s . C o n t r o l of t h e s e u n i t s t o m a i n t a i n p r o p e r combustion c o n d i t i o n s , p a r t i c u l a r l y a t low f i r e , i s f r e q u e n t l y d i f f i c u l t . I n s u f f i c i e n t a e r a t i o n of t h e f u e l and low combustion- chamber t e m p e r a t u r e s may c a u s e o n l y p a r t i a l combustion w i t h

s u b s e q u e n t d e p o s i t i o n of c o m b u s t i b l e m a t e r i a l i n smokepipes and chimneys. C o n t r o l d i f f i c u l t i e s may be a g g r a v a t e d f u r t h e r b y m u l t i p l e v e n t i n g if t h i s c a u s e s d r a f t problems and f a u l t y u n i t

o p e r a t ion. Heavy d e p o s i t s of s o o t were o b s e r v e d i n some i n s t a n c e s ( ~ i g . 2

1.

The f i e l d i n v e s t , i g a t i o n i n d i c a t e d t h a t t h e m a j o r i t y of s o o t f i r e s i n chimneys and smokepipes o c c u r r e d i n houses over 40 y e a r s of a g e , These houses a p p e a r e d t o be m o s t l y of i n i t i a l low c o s t and poor c o n s t r u c t i o n . C l e a r a n c e r e q u i r e m e n t s from chimneys and smokepipes t o a d j a c e n t combustible c o n s t r u c t i o n u s u a l l y had n o t been observed by t h e b u i l d e r s , and chimney c o n s t r ~ i c t i o n i n many houses appeared t o be s u b s t a n d a r d by p r e s e n t b u i l d i n g r e q u i r e m e n t s . The o c c u r r e n c e of s o o t f i r e s , however, d i d n o t n e c e s s a r i l y depend on poor q u a l i t y of chimney

o r house c o n s t r u c t i o n .

D e t e r i o r a t i o n of some of the o l d e r chimneys was s e v e r e . S p a l l i n g of b r i c k s and mortar decay had r e d u c e d v e r y c o n s i d e r a b l y t h e degree of s a f e t y t h a t t h e s e chinmeys c o u l d p r o v i d e . Where t h e y were i n c o n t a c t w i t h wood, h i g h f i r e danger e x i s t e d , and if s o o t f i r e s o c c u r r e d f i r e c o u l d r e a d i l y s p r e a d t o t h e b u i l d i n g . F i g u r e s 3 , 4 i l l u s t r a t e s u c h chimneys. A l l s u f f e r e d from tnasonry d e t e r i o r a t i o n and a l l were i n c o n t a c t w i t h t h e house framing.

Lack of adequa t e c l e a r a n c e t o c o m b u s t i b l e house c o n s t r u c t i o n i s common w i t h b r a c k e t chfmneys and c a u s e s t h e i r r e l a t i v e l y h i g h f i r e - h a z a r d p o t e n t i a l . The t y p i c a l method of s u p p o r t of two

such chimneys and smokepipe c o n n e c t i o n i s shown

i n

Fig.

5.

The p r o x i m i t y of p a i n t e d and d r y woodwork should be n o t e d o

C o n c l u s i o n s

The f o l l o w i n g c o n c l u s i o n s c a n be drawn from t h e above i n v e s t i g a t i o n :

1. Soot samples a n a l y s e d were r e a d i l y c o m b u s t i b l e m i x t u r e s of c a r b o n , hydrocarbons, w a t e r , e t c . w i t h p o s s i b l e i g n i t i o n t e m p e r a t u r e s (dependent on c o m p o s i t i o n ) below 300°F ( 1 5 0 ° c ) . Samples t e s t e d were a c i d i c , 2. Small tnanually c o n t r o l l e d h e a t i n g u n i t s b u r n l n g s o l i d f u e l on g r a t e s o r l i q u i d f u e l i n e v a p o r a t i v e b u r n e r s , p a r t i c u l a r l y when o p e r a t e d w i t h i n a d e q u a t e d r a f t , where more f r e q u e n t l y a s s o c i a t e d w i t h s o o t f i r e s t h a n were o t h e r h e a t i n g u n i t s . Wood f u e l a p p e a r s t h e one t o g i v e l a r g e s t quantities of s o o t w i t h l o w e s t i g n i t i o n t e m p e r a t u r e s . 3. The l a r g e s t number of s o o t f i r e s o c c u r r e d i n very cold mid-winter weather when h e a t i n g - u n i t o p e r a t i o n was most i n t e n s i v e . Many s o o t f i r e s

o c c u r r s d a l s o w i t h s . ~ a l l wood-f i r e d u n i t s i n m i l d weather w i t h l a r g e d a y - n i g h t tempera- t u r e d i f f e r e n c e s , when more i n t e n s i v e u n l t o p e r a t i o n followed a prolonged p e r i o d of low f i r e .

The m a j o r i t y of s o o t f i r e s occllrrad i n sub- s t a n d a r d chimneys and slnokepipes i n low q u a l i t y ~ O U S ~ S ~ Acknowledgment s M r . M r . I n s and The a u t h o r g r a t e f u l l y acknowledges t h e a s s i s t a n c e of D.S. R u s s e l l i n c a r r y i n g out a n a l y s i s of s o o t samples, of E.L. Mulligan i n r e c o r d i n g f i e l d i n f o r m a t i o n , and of Chief p e c t o r P h i l L a r k i n , C h i e f , F i r e P r e v e n t i o n Bureau of Ottawa

. h i s s t a f . f i n making t h e i n v e s t i g a t i o n p o s s i b l e .

Bib1 i ogra phy

Seekamp, H. and

K.

~ 8 h l e r . Brandversuche a n h a u s s c h o r n s t e i n o n a u s mauerwerk und forrnstiicken. B e r l i n ,

1956,

48 p.

Torp, A. Temperatures d u r i n g f i r e s i n chimneys w i t h s h i n i n g s o o t . Chimney Conference, Copenhagen, ~ e p o r t I ( N ) 1,

TABLE I

DETAILS OF SOOT SALPLES

Sample Sampling Heating Fuel P h y s i c a l Chemical Composition of l o c a t i o n u n i t used appearance d r y sample

i n of s o o t

v e n t i n g

%

C *

%

H* Ash

s y s tern

1 Smokepipe Cooks t ove mixed spongy, l i g h t 69 .6 4.09 _{3 06} S t r o n g t a r r y

15'

from wood w e i g h t , caked sme 1 1

u n i t on

- ~

2 Smokep i p e Grav. warm mixed g l o s s y , caked 53 08

7 ' from a i r f u r n a c e wood on, h a r d u n i t

- - - - - -

5.02 12.3 S t r o n g t a r r y s m e l l

3 Smckep i p e Grav. warm mixed g l o s s y , caked

45.9

4 . 8 6 22*9 Same sgs tern a s

41 from a ir f u r n a c e wood on, h a r d No. 2, s t r o n g

u n i t

_-

t a r r y s m e l l

4

Smokepipe Cookstove mixed g r a n u l a r p l u s

58

0 1

4.69

7.0

131 from wood powder

u n i t f i b r e -

board etc.

5

A t _{c h h - Cookstove mixed s l i g h t l y g l o s s y}

56.4

4.

_{7 1}

5.4

_{Same system}

neY wood, g r a n u l a r p l u s a s NO.

4

t h i m b l e f i b r e - l i t t l e powder board etc.

I

1

6 Chimney Grav. warm Anthraca- powder 32.8 2.63 38.2 No s m e l l

i a ir c i t e ,

$ f u r n a c e wood

f

! 7 Chimney Grav. warm Anthra- powder 36.2 3 . 4 2906

i a i r c i t e

f urna ce

8 Chimney Warm a i r Anthra- powder

35.5

3.18 35.3

f u r n a c e c i t e , damp

b i t . appearance c o a l

9 _{Smoke p i p e Spa ce- No* 1 f i n e 63.1 2 0 1 5 10.5}

h e a t e r o il powder

1 0 Smokep i p e Space- No. 1 f i n e 58.3 2.52

h e a t e r o i l powder

505

TABLE I1

FLASH AND F I R E POINTS

Sample

Smoking F l a s h F i r e Sample Tern e r a t u r e Point P o i n t

gF OF OF Remarks Heated t o 5S0°F 205 215 Burning w i t h v i s i b l e flame 205 215 Burning w i t h v i s i b l e flame Heated t o 710°F Glowing Heated t o 6 3 0 O ~ Heated t o 720°F Glowing Heated t o 700°F Glowing Heated t o 750°F Glowing Heated t o 700°F Glowing Heated t o 7 6 0 O ~ Glowing

TABLE 111

1iEIGHT LOSS ON HEATING AND A S H CONTENT

%

w e i g h t l o s s on h e a t i n g

%

r e s i d u e a f t e r s u s t a i n e d _{hea t i n a Appearance -}

_-

Sample 22 1°F-1050C 392 OF-200 O C 572°F-3000C 1 6 5 2 O ~ - 9 0 0 ~ ~ 1 9 2 2 ° ~ - 1 ~ 5 ~ 0 ~ of Ash

2 h o u r s 1 h o u r 1 h o u r 2 1/2 h o u r s

4

h o u r s Fused, g r i t t y , some i r o n Fused, g r i t t y , some i r o n Fused, g r i t t y , some i r o n Fused, g r i t t y some s o f t , l i t t l e i r o n F'used, g r i t t y , some s o f t , l i t t l e i r o n Fused, g r f t t y , l i t t l e i r o n S o f t , f l u f f y S o f t , f l u f f y Fused, g r i t t y Fused, g r i t t y

A C I D I T Y O F D E P O S I T S

Sample

pH

of s o o t sample

pH

of ash

pH

of blank Remarks

--

Blank

M s t i l l e d

H20

-

of

TABLE

V

SOOT FIRES I N

CHIMNEYS

AND SMOI-EPIPES

T Week D a t e s Mean Weekly S o o t F i r e s L i s t e d o Number

1956-57

_{O u t s i d e A i r}

Approximate Age of Houses t Tempera t u r e

O F

viiz8r10

11

t o 8 r m - f r - g ~ ~ 5 7 f

E

TABLE

VI

CHIMNEY DETAILS

M a t e r i a l of chimney w a l l s : b r i c k masonry

cemsnt chimney block Chimney l i n o r : chimney l i n e d chimney u n l i n e d Support of chimney: on f o o t i n g s by w a l l b r a c k e t Chimney l o c a t i o n i n b u i l d i n g : i n s i d e o u t s i d e Chimneys w i t h c l e a n o u t Chimneys s e r v i n g more t h a n 1 h e a t i n g a p p l i a n c e Chimneys w i t h unused smokepipe

TABLE V I I

HEATING UNITS ASSOCIATED

WITH

SOOT FIRES

I N CHIMNEYS AND SMOKEPIPES

!Type of Heating Unit Number Peroentage Cooks t o v e s Spa c e h e a t e r a G r a v i t y warm a i r f u r n a c e a C e n t r a l h o t w a t e r b o i l e r s C e n t r a l steam b o i l e r s P i p e l e a s f u r n a c e s F i r e p l a c e s Forced warm a i r f u r n a c e a T o t a l

TABLE VIII

FUEL USED IN HEATING UNITS ASSOCIATED WITH SOOT FIRES IN CWIMNEYS AND SP.'OIZEPIPES

Type of

Fuel

Heat ing uni t s us l.ng duct ing

for heat distribution Cookstoves Spaceheaters Automatic Ma nua 1

control control Ma control nua

1

Ma control nua 1

Anthracite

3

Bi twninous coal

3

Wood

Wood & Anthracite Wood &

bituminous coal Wood & Anthracite

& bituminous coal Oil

-

atomizing burner

-

original system

3

Oil

-

atomizing burner

-

converted 1 system Oil

-

vayourizing burner

r

I I I I I I I

I

I I

MEAN WEEKLY OUTSIDE AIR TEMPERATURE

--- ---

I I I I I I I I

0 2 4 6 8 10 12 14 16 18 20 22 24

WEEK NUMBERS

I

NUMBER OF SOOT FIRES I N CHIMNEYS AND SMOKEPIPES

I

WEEK NUMBERS WEEK NUMBERS 0 1 0 ' W fY

-

LL LL 5 0 0 z

FIGURE

I

I I I I I I I I 1 I I

NUMBER OF WOOD-FIRED COOKSTOVE ASSOCIATED WITH

-

SOOT FIRES

_-

0 . - D B R INT. REPT. 170 - . -

-

0 2 4 6 8 10 12 14 16 18 2 0 22 24

Figure

3 e

_{K O F ~ P F decay in chimney in oantast w i t h wood} house framing

590'7

Ffgure

se

T p i c e l

method of support of b r a c k e t o h i m e y s

s

h

owing h i g h f

ire-hazard

p o t e n t i a l a

DBR INmRMAL REPORT NO, 178