Comparison of flame-spread ratings by radiant panel tunnel furnace and Pittsburgh Corning apparatus

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Comparison of flame-spread ratings by radiant panel tunnel furnace

and Pittsburgh Corning apparatus

NATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEARCH

COMPARISON OF FLAME -SPREAD RATINGS BY RADIANT PANEL, TUNNEL FURNACE,

AND PITTSBURGH CORNING APPARATUS

by A. R o s e F i r e Study No. 22 of the D i v i s i o n of Building R e s e a r c h Ottawa June 1969

COMPARISON O F FLAME -SPREAD RATINGS B Y RADIANT PANEL, TUNNEL FURNACE,

AND PITTSBURGH CORNING APPARATUS

A. Rose

T h e s t a n d a r d North A m e r i c a n f l a m e - s p r e a d t e s t s of building m a t e r i a l s a r e those s e t f o r t h in ASTM Methods E 84 ( I ) , the s t a n d a r d tunnel t e s t ; E 162 ( 2 ) , the radiant panel t e s t ; and E 286 ( 3 ) , the

8-foot tunnel t e s t . T h e s e t e s t s r e q u i r e expensive and complex

equipment and techniques of calibration, and through the y e a r s e f f o r t s have been m a d e t o devise s i m p l e , inexpensive equipment that would give r e s u l t s c o m p a r a b l e t o those obtained with the t h r e e m a j o r methods.

Among the m o r e r e c e n t developments, the a p p a r a t u s that s e e m e d t o have the g r e a t e s t potential w a s t h a t introduced i n 1966 by M. M. Levy of P i t t s b u r g h Corning (4). T h i s simple f l a m e

-

s p r e a d testing device, called the "30/30 apparatus" because of the s i z e of s a m p l e and the slope of i t s supports ( F i g u r e s 1 , 2 , 3 ) , evolved during development w o r k on foamed p l a s t i c s f o r the Company, but w a s thought t o have wider application i n the field of building m a t e r i a l s .

In the f i r s t phase of t h i s work, i t was possible only t o c o m p a r e f l a m e - s p r e a d r a t i n g s obtained with the 30/30 a p p a r a t u s with those f r o m the r a d i a n t panel method a s t h e s e w e r e the two m e a n s available a t t h e

DBR/NRC. R e s u l t s of t e s t s on a few m a t e r i a l s that had been t e s t e d in

E 8 4 tunnel f u r n a c e s a t U n d e r w r i t e r s ' L a b o r a t o r i e s of Canada

(Scarborough) a s well a s on s o m e that had been r u n in the 8-foot tunnel f u r n a c e (3) at the F o r e s t P r o d u c t s L a b o r a t o r y (Ottawa), became available during t h i s stage of the work. T h e s e a r e included, with p e r m i s s i o n , in the r e s u l t s given i n Table I.

In spite of s o m e s e r i o u s d i s p a r i t i e s between r a d i a n t panel and 30/30 r e s u l t s , the usefulness of the l a t t e r a p p a r a t u s w a s sufficiently d e m o n s t r a t e d t o justify f u r t h e r work when the 25-foot tunnel f u r n a c e w a s i n s t a l l e d a t the NRC F i r e R e s e a r c h Section in November 1967. As m a n y a s possible of the original o r closely s i m i l a r m a t e r i a l s w e r e rechecked by a l l t h r e e m e t h o d s in the second phase of the study.

OTHER OBJECTIVES

Although the p r i m a r y purpose of this study w a s a c o m p a r i s o n of f l a m e - s p r e a d r a t i n g s by the t h r e e m e t h o d s in question, i t was a l s o c a r r i e d out t o build up a backlog of information using the 25-foot

tunnel f u r n a c e method on Canadian building m a t e r i a l s with f l a m e - s p r e a d r a t i n g s i n the 35 t o 200 range. Only a few lining m a t e r i a l s i n this r a n g e a r e l i s t e d i n the "Building Construction" section of the "List of M a t e r i a l s and Equipment" published by U n d e r w r i t e r s ' L a b o r a t o r i e s of Canada. The f l a m e

-

s p r e a d classification l i m i t s e s t a b l i s h e d f o r v a r i o u s occupancies in the National Building Code (1 965) a r e 25, 75 and 150 (5). An upper l i m i t of 1 50 f o r lining m a t e r i a l s in single -family dwellings i s being c o n s i d e r e d by r e g u l a t o r y bodies and thus the r e s u l t s i n T a b l e s Il and IU f o r wood- f i b r e ceiling t i l e s , h a r d b o a r d s and p a r t i c l e b o a r d s a r e of i n t e r e s t .

Information was a l s o r e q u i r e d a s a b a s i s f o r informed selection of m a t e r i a l s f o r the f u l l - s c a l e c o r r i d o r t e s t s being c a r r i e d out by the DBR F i r e R e s e a r c h Section (6). In m a n y of the e a r l i e r c o r r i d o r t e s t s f l a m e - s p r e a d r a t i n g s of b o a r d s t r e a t e d with f i r e - r e t a r d a n t s a l t s o r coatings w e r e r a d i a n t panel v a l u e s and not always i n good a g r e e m e n t with E 84 r a t i n g s established l a t e r .

THE PITTSBURGH CORNING APPARATUS

A s i n the l a r g e - s c a l e tunnel f u r n a c e methods, Levy used suitably conditioned r e d oak a s the "100 standard" and a s b e s t o s - c e m e n t board a s the "zero standardIt i n the 4-minute t e s t . He did not specify any p a r t i c u l a r humidity o r t e m p e r a t u r e range, but i t was a s s u m e d t h a t the conditions w e r e 48 t o 52 p e r cent R.H. and 68 t o 72 deg F. (Typical calculations of f l a m e - s p r e a d r a t i n g s and a r e d oak c a l i b r a t i o n r u n a r e given i n Appendix A.

1

The p r a c t i c a l upper limit of the t e s t i s a f l a m e - s p r e a d rating (FSR) of about 135; although Levy includes r a t i n g s a s high a s 150.

Typical h a r d b o a r d s and p a r t i c l e b o a r d s with r a t i n g s i n t h i s r a n g e produce f l i c k e r i n g f l a m e f r o n t s which a r e difficult to r e a d a s they a p p r o a c h the end of the box. E s t i m a t i o n of the t i m e r e q u i r e d t o r e a c h the 22- o r 23-in. m a r k w a s not found s a t i s f a c t o r y a s a method of establishing r e l a t i v e r a t i n g s

above 140.

B e c a u s e p r o g r e s s of the f l a m e f r o n t i s o b s e r v e d through the

opening i n the u p p e r end of t h e box ( F i g u r e 3), obscuration o r obliteration of t h e 1 -inch-interval m a r k i n g s by heavy smoke o r smoke d e p o s i t s m a y l i m i t the u s e f u l n e s s of the a p p a r a t u s , a s i s often the c a s e when testing p l a s t i c s and painted products. Expedients f o r overcoming t h i s difficulty will be d i s c u s s e d l a t e r .

Although Levy c l a i m e d s a t i s f a c t o r y c o r r e l a t i o n between the values obtained using the 30/30 a p p a r a t u s and those with the E 84 tunnel f u r n a c e , m o s t of h i s E 84 values f o r wood-based m a t e r i a l s w e r e b a s e d on published r a t i n g s r a t h e r than on the r e s u l t s of p a r a l l e l r u n s on m a t c h e d s a m p l e s , and unfortunately s o m e of t h e s e published values a r e open t o question. F o r t h i s r e a s o n the p r e s e n t study w a s designed t o c o v e r a s broad a range of m a t e r i a l s a s possible.

T H E D B R T U N N E L F U R N A C E

The DBR tunnel f u r n a c e ( F i g u r e s 4, 5) w a s patterned a f t e r t h a t i n s t a l l e d a t the r e s e a r c h c e n t r e of the National Gypsum Company at Buffalo, N. Y. Some modifications we r e unavoidable because of s p a t i a l l i m i t a t i o n s and the n e c e s s i t y of connecting the f u r n a c e t o an existing 6000-cfm exhaust fan.

The o r i g i n a l exhaust s y s t e m m a d e m a n u a l control of the d r a f t a t the specified l e v e l v e r y difficult o v e r the 10-minute c o u r s e of the t e s t when the m a t e r i a l s being t e s t e d w e r e of high fuel value, such a s

h a r d b o a r d s and p a r t i c l e b o a r d s . T h i s difficulty, although i t unquestionably reduced the r e l i a b i l i t y of t h e "smoke density" (SD) values i n Table 11-B, is probably not a s g r e a t a s o u r c e of e r r o r in the r e s u l t s l i s t e d under "flame s p r e a d classification1' (FSC) o r "fuel contributed" ( F C ) . Red oak flooring is the "100 standardtt f o r a l l t h r e e values, hence any i n c r e a s e i n the absolute value of the smoke d e n s i t y due to a reduction in tunnel d r a f t and a i r velocity during the c o u r s e of a c a l i b r a t i o n t e s t on oak would be m a t c h e d by a proportionate i n c r e a s e f o r o t h e r m a t e r i a l s .

T h i s difficulty w a s o v e r c o m e by the installation of a 16-inch- d i a m e t e r b a r o m e t r i c d a m p e r between the manually -operated control d a m p e r and the exhaust fan. Control of the d r a f t w a s f u r t h e r improved

by the addition of a pneumatically -controlled d a m p e r between the b a r o m e t r i c d a m p e r and the f a n . T h e s e modifications w e r e m a d e before the t e s t s

r e p o r t e d in Table 111-B w e r e begun. The a v e r a g e absolute value f o r the smoke d e n s i t y f o r r e d oak flooring w a s reduced about 50 p e r c e n t , but the c o m p a r a b l e SD values f o r such m a t e r i a l s a s unfinished $-in. Douglas fir plywood and p a r t i c l e b o a r d R i n T a b l e s 11-B ( s a m p l e s 46 and 47) and 111-B ( s a m p l e 85) a r e i n r e a s o n a b l e a g r e e m e n t .

T h e effect of v a r i a t i o n s in tunnel d r a f t and a i r velocity on SD values h a s been thoroughly covered i n the c o u r s e of smoke obscuration

Standardization with Red Oak and Influence of F u e l Rate

In t h e calibration of the tunnel f u r n a c e with 13/ 16-in. r e d oak flooring, the t i m e in which the f l a m e f r o n t i s r e q u i r e d t o r e a c h the end ( a net advance of 19. 5 f e e t ) i s 5. 5 f 0.25 m i n u t e s . The

t i m e i s d e t e r m i n e d by the attainment of a t e m p e r a t u r e of 980 deg F a t the vent-end thermocouple, which i s located 1 foot f r o m the end of and 1 in. below the sample. With due allowance f o r the variability of the oak and the inevitable e r r o r s in m e a s u r e m e n t , the t i m e s

obtained in the m o s t r e l i a b l e r u n s w e r e found t o be strongly dependent on the g a s feed-rate t o the T e e - b u r n e r . T o k e e p the "red oak time" within the p e r m i s s i b l e r a n g e it i s n e c e s s a r y t o c o n t r o l the fuel input (including t h a t of t h e pilot b u r n e r ) within the l i m i t s 4385 f 35 ~ t u / m i n .

o r 4.362 *O. 035 s t a n d a r d cubic f e e t of n a t u r a l g a s p e r minute a t 1005 Btu p e r s t a n d a r d cubic foot. It w a s n e c e s s a r y to r e p l a c e the o r i g i n a l p r e s s u r e r e g u l a t o r i n the g a s t r a i n with a m o r e p r e c i s e device, and t o u s e a 314-in. needle valve f o r fine adjustment of the g a s r a t e t o compensate f o r changes in b a r o m e t r i c p r e s s u r e .

When the a v e r a g e fuel r a t e during a 1 0-minute t e s t r u n deviated significantly f r o m 438 5 ~ t u / m i n . within the s e l i m i t s , a n "equivalent r e d oak time" w a s used i n calculating f l a m e s p r e a d c l a s s i f i c a t i o n s over 100, t h a t is, w h e r e the f l a m e front r e a c h e d the end of the tunnel i n l e s s than 5.5 m i n u t e s (Appendix B).

In the c a s e of m a t e r i a l s o t h e r than r e d oak, the t i m e t o r e a c h the 25-foot m a r k i s d e t e r m i n e d visually. The difficulty of deciding on the t i m e f o r the f l a m e f r o n t t o r e a c h t h i s point i s i n c r e a s e d by fouling of the windows by smoke in m a n y c a s e s . The r e s e a r c h staff a t the National Gypsum Company suggested the addition of a s m a l l window in the f l o o r of the f u r n a c e just beyond the 25-foot m a r k . In the DBR/NRC f u r n a c e the s e a l e d window w a s inclined s o a s t o sight on the 25-foot m a r k , the s a m p l e s used being actually 2 5 f t 3 in. i n length.

T h i s a r r a n g e m e n t h a s given visual "red oak t i m e s " in excellent a g r e e m e n t with the 980-deg point, and the a g r e e m e n t i s usually good f o r o t h e r unpainted wood-based m a t e r i a l s . Nine of the twenty m a t e r i a l s in Table 11-B with FSC1s of 100 o r higher w e r e run a f t e r the installation of t h i s window.

Ignition T i m e

The ignition t i m e , I T , ( T a b l e s 11-B and III-B) i s not a r e q u i r e d observation in E 84 t e s t s . B e c a u s e of the p a r t i c u l a r window construction

employed in the DBR tunnel f u r n a c e i t i s s o m e t i m e s difficult to d e t e r m i n e . Other tunnel f u r n a c e o p e r a t o r s r e c o r d i t a s an index of e a s e of ignition, and t h i s was done whenever possible in this study.

The ignition t i m e f o r r e d oak flooring in the DBR tunnel f u r n a c e i s 4 5 t o 60 seconds.

THE RADIANT PANEL APPARATUS

The DBR r a d i a n t panel a p p a r a t u s ( F i g u r e s 6,7) h a s been used o v e r the p a s t seven y e a r s i n the evaluation of a wide v a r i e t y of m a t e r i a l s . It h a s been used i n acceptance testing of m a r i n e deck and bulkhead

m a t e r i a l s , a d h e s i v e s and coatings, a s well a s in investigational work f o r f i r e a u t h o r i t i e s w h e r e the s i z e of s a m p l e available was limited. In the c a s e of s o m e p l a s t i c s and synthetic c a r p e t s i t h a s given f l a m e - s p r e a d indexes differing widely f r o m the corresponding E 84 ratings.

A s the construction and operation of the radiant panel a r e d e s c r i b e d i n ASTM E 162, only a d i s c u s s i o n of the method of calculating the t h r e e f l a m e - s p r e a d indexes used in the DBR study will be included in t h i s r e p o r t .

T h e calculation of the s i m p l e a r i t h m e t i c index Isl f o r a s p e c i m e n of fir plywood i s d e m o n s t r a t e d in Appendix C. T h i s index i s the product of a f l a m e - s p r e a d f a c t o r Fs and a heat evolution f a c t o r , Q. Q i s a function of T , the m a x i m u m t e m p e r a t u r e r i s e during the 15-minute t e s t period above t h e b a s e t e m p e r a t u r e r e c o r d e d with a n a s b e s t o s - c e m e n t board in the s a m p l e holder. The t e m p e r a t u r e r i s e i s r e a d by m e a n s of seven thermocouples in p a r a l l e l in the s t a c k above the panel.

The second index, Is,, i s a computer -calculated value based on the s e m i - l o g a r i t h m i c c o r r e c t i o n plot suggested i n Section 8 ( e ) of ASTM E 1 62

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67. It is designed t o give m o r e reasonable approximations when ignition of the

s a m p l e by the acetylene pilot f l a m e i s a b n o r m a l l y rapid o r slow, i. e . , when tg (the t i m e , in m i n u t e s , t o r e a c h the 3-in. m a r k ) i s a b n o r m a l l y high o r low in r e l a t i o n t o t 6 , tg, e t c . , in a plot of d, (the d i s t a n c e t r a v e l e d , in i n c h e s ) a g a i n s t log t. Is, a l s o n o r m a l i z e s the relationship where e r r a t i c

propagation of the f l a m e f r o n t o c c u r s , e. g . , in c a s e s w h e r e rapid flashing p a s t the 3 - , 6 - , o r 9-in. m a r k s i s followed by a m o r e r e g u l a r advance to the 1 2 - and 15-in. m a r k s .

When r a p i d flashing p a s t the 3- o r 6-in. m a r k i s followed by

r e t r o g r e s s i o n and then development of a sustained and n o r m a l l y p r o g r e s s

-

ing f l a m e f r o n t , two independent s e t s of calculations a r e usually m a d e ( s e e s a m p l e s Nos, 48 and 58, Table

11-B).

The t h i r d index Is3 w a s designed by G. Williams-Leir of the DBR F i r e R e s e a r c h Section t o put into effect the principle t h a t 'no s p e c i m e n should be given a higher f l a m e - s p r e a d index than it would have had if the f l a m e front had p a s s e d any m a r k e a r l i e r than it actually did. It follows that index 3 cannot be g r e a t e r than index 1; the difference m a y be z e r o and i s usually small. The t h i r d index g i v e s b e t t e r a g r e e m e n t with the E 84 r a t i n g s in the c a s e s of s o m e unfinished cellulosic m a t e r i a l s but among the m a t e r i a l s considered h e r e i t only b e c o m e s significantly lower than the f i r s t index i n the c a s e of s o m e of the m o r e f l a m m a b l e c a r p e t s and p l a s t i c s .

PREPARATION O F MATERIALS AND SAMPLING PLAN

Whenever factory-finished lining m a t e r i a l s could be conveniently obtained f r o m l o c a l s o u r c e s they w e r e included in the p r o g r a m . B o a r d s not f a c t o r y -finished w e r e r o l l e r -coated with c o m m e r c i a l flat, s e m i - g l o s s o r g l o s s alkyd paints a s r e q u i r e d , except in the c a s e of the ceiling t i l e s l i s t e d in Table

III,

w h e r e a light r o l l e r coat of an intumescent l a t e x paint w a s applied.

Since two 4 - by 8 - f t panels w e r e r e q u i r e d f o r e a c h tunnel f u r n a c e t e s t , the sampling plan used ( F i g u r e 8) p e r m i t t e d the averaging of the r e s u l t s f o r eight r a d i a n t panel and s i x P i t t s b u r g h Corning s p e c i m e n s of e a c h m a t e r i a l . T h i s s c h e m e could not be followed in the c a s e of c a r p e t s , foamed vinyl wall c w e r i n g ( s a m p l e No. 63), prefinished hardboard siding ( s a m p l e No. 56), and ceiling t i l e s ( s a m p l e s Nos, 8 8 t o 95).

A m i n i m u m of four s p e c i m e n s i s r e q u i r e d f o r the r a d i a n t panel and t h r e e f o r the P i t t s b u r g h Corning t e s t , but w h e r e 4 - by 8-ft panels w e r e used, the n u m b e r was i n c r e a s e d to eight and s i x s p e c i m e n s , respectively. T h i s w a s justified by the variability and e r r a t i c f l a m e f r o n t propagation encountered in the c a s e of m a n y painted b o a r d s in both t e s t s .

All l a b o r a t o r y -painted s a m p l e s w e r e d r i e d thoroughly i n f r e e l y circulating a i r , then conditioned f o r a t l e a s t 30 d a y s , again with good ventilation, before testing. Samples f o r the tunnel f u r n a c e w e r e

conditioned a t 35 t o 40 p e r cent R. H., 73 to 75 deg F, and f o r the o t h e r t e s t s a t 48 t o 52 p e r cent R.H., 68 t o 70 deg F.

DISCUSSION O F RESULTS

The d i v e r s i t y of m a t e r i a l s covered in t h i s study p r e c l u d e s any s i m p l e a n a l y s i s of the r e s u l t s . No t e s t i s capable of producing meaningful

Galues f o r a l l types of m a t e r i a l s , p a r t i c u l a r l y i f carpeting, plastic f o a m s and composite products a r e included.

Because r e d oak l u m b e r o r flooring i s the "1 00 standard" i n a l l t h r e e t e s t methods, i t is t o be expected that a g r e e m e n t among t h e m will be good f o r m o s t unfinished cellulosic products. (In the c a s e of the radiant panel t e s t , r e d oak was used t o e s t a b l i s h the original

p a r a m e t e r s i n the development of the equipment by the National B u r e a u of Standards. It is not a s a t i s f a c t o r y m a t e r i a l for r e c a l i b r a t i o n purposes. An o i l - t e m p e r e d $-in. hardboard with Is = 150 was distributed by NBS a s a secondary standard. When the supply of t h i s board w a s exhausted, a new m a t e r i a l with Is = 20 5 was m a d e available. )

(1 ) Wood-based P r o d u c t s

, F o r unfinished cellulosic products containing inorganic f i r e r e t a r d a n t s ( s a m p l e s Nos. 17, 18, 52, 53) the radiant panel t e s t gives inordinately low r a t i n g s i n relation t o E 84 classifications, while the 30/30 t e s t is the r e v e r s e . The intense radiation a t the top of the sample i n the E 162 t e s t often produces pronounced c h a r r i n g without any m e a s u r a b l e f l a m e s p r e a d i n such c a s e s . The high values obtained in the 30/30 t e s t a r e due i n p a r t t o coloration of the flame by the s a l t s p r e s e n t . This opinion is supported by another Canadian u s e r of the device.

In the c a s e of p a r t i c l e b o a r d sample No. 53, a f u l l - s c a l e c o r r i d o r t e s t

( 6 )

strongly supported the 30/30 and E 84 values.

( 2 ) Effects of Coatings

Where conventional low

-

o r s e m i -glos s oil -base paints a r e applied t o wood-based products, the radiant panel indexes a r e always

substantially lower than the r a t i n g s found by the other t e s t s ( s a m p l e s Nos. 44, 49, 51, 65 t o

68,

70, 74, 76, 77, 86). With high-gloss alkyd e n a m e l s , the values a g r e e m u c h b e t t e r f o r b o a r d s over $ in. in thickness ( s a m p l e s Nos. 45, 55, 71). T h i s behaviour d e s e r v e s f u r t h e r comment.

It should be emphasized that in the 4-minute 30/30 t e s t , in which 1

a z-in. a s b e s t o s - c e m e n t board i s placed on top of the sample, cellulosic m a t e r i a l s , even those a s thin a s 1/8 in., a r e seldom penetrated by the impingeing b u r n e r flame. In t h e radiant panel t e s t , which continues f o r

1 5 m i n u t e s if not t e r m i n a t e d sooner because the descending f l a m e f r o n t h a s r e a c h e d the 15-in. m a r k , unfinished $-in. b o a r d s a r e usually pene- t r a t e d by the pilot f l a m e well before the end of the t e s t . The upper t h i r d of t h e s a m p l e m a y , i n the c a s e of h a r d b o a r d s and p a r t i c l e b o a r d s , be

a l m o s t totally consumed. The application of a finish, even a coat of g l o s s alkyd enamel, p r e v e n t s t h i s penetration in m a n y c a s e s ( s a m p l e s No. 22, 40, 42).

In the 10-minute tunnel furnace t e s t ,

5-

and 3/8-in. Douglas f i r plywood and hardboards a r e penetrated by the burner flame. Gloss o r semi-gloss alkyd enamels on +-in. plywood lead to a high FSC because the back of the sample becomes involved for some distance along i t s length (samples Nos. 40 t o 42).

1

Douglas fir plywood, z-in. o r m o r e in thickness, i s usually not penetrated by the flame and is preferable t o thinner panels a s a substrate f o r evaluating the effects of conventional coatings.

The agreement among the three methods in the case of gloss alkyd enamels on $-in. plywood and particleboard in a few c a s e s (samples Nos. 45, 55) m a y be due to the countervailing effects in the radiant panel t e s t of reflectivity and a b a r r i e r action on the one hand and the easy ignitability and high fuel value of the coating on the other.

G r o s s and Loftus of the National Bureau of Standards prefer $-in. oil-tempered hardboard f o r comparisons of the effects of conventional and f i r e -retardant paints in the radiant panel method (8). Their values f o r

Is,

,

in the case of conventional coatings on )-in. hardboard and

plywood, a r e generally in agreement with those obtained in this study

(9).

The m o s t satisfactory agreement among the three methods i s found with factory-finished low-density fibreboard panels and ceiling t i l e s (samples Nos. 57, 58, 87, 88, 92).

(3) Floor Coverings and Foamed P l a s t i c s

The problem of selecting a r e a l i s t i c flame-spread t e s t for floor coverings has become urgent with the introduction in recent y e a r s of highly flammable synthetic carpet m a t e r i a l s . The r e s u l t s in Tables I and 11 emphasize the complexity of the problem.

The r e s u l t s f o r closed-cell polyvinyl chloride foam wall coverings (samples Nos. 28, 63) can be taken a s an example of the disparities to be expected in the plastics field, as emphasized recently by Collishaw (1 0). Results of a full-scale c o r r i d o r t e s t

and a "corner-wall" t e s t c a r r i e d out by J. H. McGuire of the DBR/NRC F i r e Research Section supported the 30/30 and E 84 t e s t s a s being the m o r e realistic for the

P V C

foam m a t e r i a l .

It should be pointed out in f a i r n e s s to the E 162 and 30/30 t e s t s , particularly in the case of PVC foam m a t e r i a l and of some c a r p e t s , that the r a t e of advance of the flame front in the tunnel furnace m a y be very high f o r brief intervals even though the flame fails t o r e a c h the 25-foot mark. This r a t e i s not taken into consideration, except a s p a r t of the

r e c o r d of t e s t , in ratings below 100, but m a y be a useful m e a s u r e of flash hazard.

CONCLUSIONS AND RECOMMENDATIONS (1) The P i t t s b u r g h Corning Apparatus

In a g r e a t m a n y c a s e s involving unfinished l u m b e r and plywood, other wood products coated with conventional paints, factory -finished f i b r e b o a r d ceiling t i l e s , and s o m e carpeting, t h i s device gives r a t i n g s which f a l l between those obtained in the other two t e s t s . In the c a s e of wood products in g e n e r a l , t e s t s using t h i s apparatus tend to n a r r o w the

range of f l a m e - s p r e a d ratings vis-2-vis the tunnel furnace and t o group the FSR values around the 100 m a r k .

Some of t h e difficulties encountered with m a t e r i a l s emitting heavy smoke have a l r e a d y been suggested. A number of expedients w e r e used t o m i n i m i z e t h i s problem, e. g., the i n s e r t i o n of s t a p l e s o r metal-headed m a p pins a t the 1-in. m a r k s f o r c a r p e t s and p l a s t i c s , heavy incising of the l i n e s on painted hardboards, o r punching of an identifying a r r a y of points along t h e s e lines.

The estimation of f l a m e f r o n t advance in the c a s e of v e r y glossy s u r f a c e s o r those of low FSR was improved by the mounting of a 6-watt l a m p and a s m a l l m i r r o r i n the t r i a n g u l a r vent a t the exhaust end of the box ( F i g u r e 1).

The m o s t logical solution t o the p r o b l e m of smoky m a t e r i a l s , g l o s s y o r textured s u r f a c e s , o r low f l a m e - s p r e a d s followed by rapid r e t r o g r e s s i o n , is the installation of a suitably m a r k e d h e a t - r e s i s t a n t window below the s a m p l e support. T h i s is the principal f e a t u r e of the m o r e sophisticated and expensive Monsanto 2-ft tunnel (1 1). To

facilitate reading of f l a m e t r a v e l a n d t o i n c r e a s e p r e c i s i o n i n the range of 2 5 t o 75, t h i s a p p a r a t u s h a s been extensively modified by the Abitibi R e s e a r c h C e n t r e and t h e Ontario R e s e a r c h Foundation, both a t Sheridan P a r k , Ontario.

Lengthening of the P i t t s b u r g h Corning a p p a r a t u s t o p e r m i t e s t i m a t i o n of FSR1s o v e r 1 50 might l e a d t o difficulties with m a t e r i a l s of low f l a m e - s p r e a d , but adding a suitable window might solve t h i s and other p r o b l e m s , and will be t r i e d l a t e r .

( 2 ) The E 84 Tunnel F u r n a c e

Although modifications and improvements i n the design and operation have been c a r r i e d out during the c o u r s e of the p r e s e n t study, t h e r e have been no r e a l opportunities t o c o m p a r e r e s u l t s f r o m the DBR f u r n a c e with those f r o m other installations with the exception of t h r e e types of carpeting and two o t h e r m a t e r i a l s . No c l a i m s f o r the validity of the r e s u l t s of t h i s study (Table

U)

will be m a d e until t h e proposed

round-robin t e s t p r o g r a m involving eight other tunnels has been completed and analysed.

It

is hoped t h a t t h i s can be done by l a t e October 1969.

In anticipation of t h i s p r o g r a m s o m e m i n o r modifications, p a r t i c u l a r l y i n the smoke m e a s u r i n g installation, a r e to be m a d e a s well a s changes i n the T e e - b u r n e r a s s e m b l y t o produce m o r e s y m m e t r i c a l f l a m e

impingement on the s a m p l e and allow e a s i e r determination of the ignition time.

(3)

The Radiant P a n e l Apparatus

Although the d i s p a r i t i e s between the r e s u l t s f r o m t e s t s using the r a d i a n t panel and tunnel f u r n a c e on s u c h common m a t e r i a l s a s painted plywood and h a r d b o a r d m a y a p p e a r t o be c a u s e f o r s e r i o u s concern, i t should be emphasized that t h e s e d i s p a r i t i e s a r e not e n t i r e l y due to d i f f e r e n c e s i n the design of the r e s p e c t i v e a p p a r a t u s e s . The calculation of the f l a m e - s p r e a d classification in tunnel f u r n a c e t e s t s where the f l a m e f r o n t d o e s not r e a c h the 25-ft m a r k , o r r e a c h e s i t i n m o r e than

5. 5 but l e s s than 10 m i n u t e s , i s highly a r b i t r a r y and f a r f r o m r a t i o n a l (Appendix B). It i s the r e s u l t of m a n y y e a r s of c o n t r o v e r s y and

c o m p r o m i s e i n ASTM c o m m i t t e e m e e t i n g s . M o r e logical m e t h o d s of

calculation have been suggested which would lead t o m u c h b e t t e r a g r e e m e n t between r a d i a n t panel and tunnel f u r n a c e r a t i n g s in the range 2 5 t o 100 within which f a l l m a n y of the conventionally painted wood products included i n t h i s study.

The e x c e s s i v e l y low o r high f l a m e - s p r e a d indexes obtained in r a d i a n t panel t e s t s on m a n y of the l e s s common m a t e r i a l s will not l i m i t its continuing u s e in acceptance testing of a i r c r a f t and m a r i n e m a t e r i a l s o r o t h e r specialized products. Where l i m i t e d amounts of m a t e r i a l a r e available i n investigational work, the g r e a t e r range of the radiant panel will give it s o m e advantages o v e r the P i t t s b u r g h Corning a p p a r a t u s . As d e m o n s t r a t e d i n t h i s study, however, m a n y of i t s r e s u l t s will be accepted but with r e s e r v a t i o n s .

REFERENCES

ASTM E 84-68. Surface Burning C h a r a c t e r i s t i c s of Building M a t e r i a l s .

ASTM E 162-67. Surface F l a m m a b i l i t y of M a t e r i a l s Using a Radiant E n e r g y Source.

ASTM E 286-65T. S u r f a c e F l a m m a b i l i t y of Building M a t e r i a l s Using a n 8 - f t ( 2 . 4 4 - m ) Tunnel F u r n a c e .

Levy, M.M. A Simplified Method f o r Determining F l a m e Spread. F i r e Technology, Vob.

3,

F e b r u a r y 1967.

National Building Code of Canada 1965. P a r t 3, Use and Occupancy, p a r a g r a p h s 3.3.1.1 ( 7 ) , 3.3.4. 5 and 3.4.2.12 (1 ).

M c G u i r e , J.H. The Spread of F i r e i n C o r r i d o r s . F i r e Technology, Vol. 4, M a y 1968.

U n d e r w r i t e r s ' L a b o r a t o r i e s , Inc. Study of Smoke Ratings Developed i n Standard F i r e T e s t s i n Relation t o Visual

Observations. ULI Bulletin of R e s e a r c h No. 56, A p r i l 1965. G r o s s , D. and Loftus, J . J. Surface F l a m m a b i l i t y of F i r e - R e t a r d a n t and Conventional P a i n t A s s e m b l i e s . F i r e R e s e a r c h A b s t r a c t s and Reviews, Vol. 3, 1961.

G r o s s , D. and Loftus, J. J . F l a m e S p r e a d P r o p e r t i e s of

Building F i n i s h M a t e r i a l s . ASTM Bulletin No. 230, May 1958. Collishaw, A. H. F l a m e Spread T e s t s on F o a m P l a s t i c

M a t e r i a l s . Dept. of the A r m y (USA). Technical Report No. 4-71. October 1968.

V a n d e r s a l l , H. L. The Use of a S m a l l F l a m e Tunnel f o r

Evaluating F i r e Hazard. J o u r n a l of P a i n t Technology, Vol. 39, August 1967.

SOME ABBREVIATIONS USED IN TABLES FSC f l a m e s p r e a d classification,

E

84 F C f u e l contributed,

E

84 SD smoke density, E 84 IT ignition t i m e , E 84 FSR f l a m e s p r e a d rating, P i t t s b u r g h Corning f l a m e s p r e a d f a c t o r , E 162 h e a t evolution f a c t o r , E 162 f l a m e s p r e a d index, E 162

T A B L E I

PITTSBURGH CORNING, RADIANT P A N E L AND TUNNEL FURNACE RATINGS ON MISCELLANEOUS MATERIALS S a m p l e No. M a t e r i a l F S R I s P C E 162-67 F S C I s * E 8 4 - 6 7 E 286-65T F i b r e b o a r d A, + - i n . , 14.7 pcf, unfinished F i b r e b o a r d A, ;-in., f a c t o r y finiah ( l a t e x p r i m e r ) rough s u r f a c e F i b r e b o a r d A, )-in., f a c t o r y f i n i s h ( l a t e x p r i m e r ) s m o o t h s u r f a c e o v e r 140 6 5 H a r d b o a r d , t e m p e r e d $-in. 63.3 pcf (NBS 150 etd)

H a r d b o a r d , t e m p e r e d $-in. (softwood pulp). 65.6 pcf

H a r d b o a r d , t e m p e r e d $-in. (softwood pulp), alkyd p r i m e r , 65.6 pcf

H a r d b o a r d eiding A, 0.367-in., 54.1 pcf, unfinished

H a r d b o a r d eiding B, 0.328-in., unfinished H a r d b o a r d siding C, 0.330 -in. , 58.7 pcf, unfinished

H a r d b o a r d siding C , 0.330-in., white alkyd p r i m e r ( f a c t o r y f i n i s h ) H a r d b o a r d siding D, 0.365-in., 59.0 pcf, unfinished H a r d b o a r d eiding Dl 0.350-in., 62.4 pcf. white g l o s s u r e t h a n e f i n i s h H a r d b o a r d siding Dl 0.353-in., 62.6 pcf, o v e r 140 o v e r 140 o v e r 140 131 g r e e n g l o s s u r e t h a n e f i n i s h P a r t i c l e b o a r d A, 0.750-in., 35.5 pcf, a s p e n p o p l a r f l a k e s P a r t i c l e b o a r d R, 0.760-in. , 46.7 pcf, m i x e d h a r d and softwood c h i p s P a r t i c l e b o a r d S, 0.688-in., 40.0 pcf, a s p e d b i r c h f l a k e s P a r t i c l e b o a r d X, 0.438-in.

,

41.4 pcf, b o r a t e f i r e - r e t a r d a n t t r e a t m e n t , a s p e n o v e r 140

- -

- -

3 5 ULC* 3 5 F P L

Douglas f i r plywood, $-in., f i r e r e t a r d a n t t r e Douglas f i r plywood, $-in., 2 c o a t s

i n t u m e s c e n t f. r . l a t e x paint Q 15-20 ULC

- -

2 5 ULC

-

-

S t r a w r o o f b o a r d , 2-in., f i r e r e t a r d a n t c o r e and p a p e r s u r f a c e s M i n e r a l a c o u s t i c t i l e 5/8-in.. 27 pcf, white f a c t o r y f i n i s h

Douglas f i r plywood, $-in., sanded Douglas f i r plywood, +-in., sanded Douglas f i r plywood, 3/4-in. , sanded. sapwood f a c e

Douglas f i r plywood, 3/4-in., s a n d e d , heartwood f a c e

- - 34 F P L

20-25 ULC

- -

Arnabilis f i r l u m b e r , 1 -in. Red pine l u m b e r , 1 -in.

Wall c o v e r i n g , P V C f o a m , 0.08-in., 1 5 pcf, c e m e n t e d t o g y p s u m b o a r d C a r p e t . wool, s t a p l e d t o 3/8-in. g y p s u m b o a r d C a r p e t , nylon, s a m e backing C a r p e t , c e l l u l o s e t r i a c e t a t e f i b e r , s a m e backing C a r p e t , polypropylene f i b e r , s a m e backing C a r p e t , a c r y l i c f i b e r , s a m e backing 119 o v e r 140 o v e r 140

: _{T y p i c a l l i s t i n g s f r o m "List of M a t e r i a l s a n d Equipment," U n d e r w r i t e r s ' L a b o r a t o r i e s of Canada.}

S c a r b o r o u g h . Ontario.

TABLE 1ZA Sample No. 34 3 5 36 3 7 38 39 40 41 42 4 3 44 45 46 47 48 49 50 5 1 52 5 3 54 55 56 57 58 59 60 6 1 62 63

MATERIALS LLST AND TREATMENT

Material and Treatment

Douglas f i r plywood, f -in., sanded, Lot A

Douglas f i r plywood, $-in., sanded, Lot A (Duplicate) Douglas f i r plywood, :/8-in., sanded, Lot B

Douglas f i r plywood, f-in., sanded, Lot C

Douglas f i r plywood, $-in., sanded, Lot D, thick face veneer Douglas f i r plywood, :/4-in., sanded, Lot E

Douglas fir plywood, 3-in., roller-coated both sides with 2 coats semi-gloss alkyd S, green Douglas f i r plywood, 4-in., same a s 40 (Duplicate)

Douglas fir plywood,

1

-in.

,

roller -coated both side s with 2 coats gloss alkyd L, green Douglas f i r plywood, f-in., Lot F , unfinished

Douglas f i r plywood, +-in., Lot F, 2 roller coats of flat alkyd F, green Douglas f i r plywood, f-in., Lot F, 2 roller coats of gloss alkyd L, green

Particleboard R, 11/16-in., 39.2 pcf, mixed hardwood and softwood chips, urea r e s i n binder Particleboard R, reverse a i d e of 46 (t'bark'' a i d e )

Particleboard K, $-in., 45.0 pcT, 3-layer, cedar chips, u r e a resin binder, unfinished Particleboard K, *-in.

,

48.1 pcl, as above w i t h factory-applied brown p r i m e coat Particleboard K , $-in., 44.4 pcf, a 8 above w i t h parchment paper overlay

Particleboard K, h - i n . , 4 6 . 8 pcf, as above with translucent factory-applied s e a l e r coat

Particleboard X, 7/ 16-h. , 4 1.4 pcf, aspen flakes, u r e a resin binder, borate fire-retardant treatment Particleboard X, as i n 52 but later production (Lot G)

Particleboard X, Lot G, with 2 r o l l e r coats of flat alkyd F, green Particleboard X, Lot G, with 2 roller coats of gloss alkyd L, green

Hardboard siding E , 0.335 in., 62.4 pcf, white semi-gloss urethane finish (cf. Sample 12, Table I) ~ i b r e b o a r d A, )-in., 18 pcf, white latex-clay factory finish

Fibreboard A, f -in., 18 pcf, white latex-clay factory finish. l a t e r production than 57 Fibreboard A, 17.5 pcf, unfinished

Carpet, cellulose triacetate fiber (cf. Sample 31)* Carpet, nylon*

Carpet, acrylic shag*

Wall covering, PVC foam, 0.08 in. thick, 15 pcf, cemented t o 3/8-in. gypsum board.

TABLE LIB

COMPARISON OF FLAME SPREAD TESTS

Sample E 162 Radiant Panel T e s t Pittsburgh Corning E 84 Tunnel Furnace R e m a r k s No. Q Isl IS2 Is3 30/30Apparatus FSC F C SD IT,

FS R sec. over 140 over 140 over 140 over 140

-

- over 140

- -

7 7

137 126 47 59 f-in. fir plywood 145 119 51 7 0 7-in. f . fir plywood

130 104 72 60 3/8-in, f i r plywood 94 108 47 65 1 .

f-in. fir plywaod

119 121 40 64 $-in. fir plywood 84 7 5 29 47 3/4-in. fir plywood 175 96 60 39 165 92 61 28 211 92 52 2 3 93 93 64 48 ;-in. f i r plywood 73 49 72 34 80 73 79 24 91 96 100 60 158 121 109 60 131 115 75

- -

31 28 14

-

-

no flame front 56 35 27

- -

no flame front 46 27 0 6 5 67 40 35 4 5 611 4 5 62 30 72 27 132 150 1000 33 - - 7 41 7 1 1 8 <5 cf. Sample 28 F l a s h flame Sustained flame

TABLE YUA

MATEFUALS LIST AND TREATMENT Sample Material and Treatment

No.

64 Douglas f i r plywood, f -in. unfinished

65 Douglas f i r plywood, +-in. plus one coat flat alkyd F, g r e e n 66 Douglas f i r plywood, $-in. plus two coats flat alkyd F , g r e e n 67 Douglas f i r plywood, $-in. plus t h r e e coats flat alkyd F, g r e e n

68 Douglas f i r plywood, $-in. plus one coat flat alkyd F and one coat semi-gloss alkyd D, g r e e n 69* Douglas f i r lumber, nominal 1 x 4 T & G (3/4 x 3 i in. ) Grade C and better

70 Douglas f i r lumber, plus one coat flat alkyd F, g r e e n

7 1 Douglas f i r lumber, plus one coat flat alkyd F and one coat semi-gloss alkyd D, green 72 Hardboard Y, nominal *-in. (0.230 in. ), screenback type, 62.3 pcf, unfinished 73 Hardboard Y, plus one coat flat alkyd F , green

74 Hardboard Y, plus one coat flat alkyd F and one coat gloss alkyd L, green 7 5 Hardboard Z, nominal f -in. (0.218 in. ) screenback, 61.2 pcf, unfinished 76 Hardboard Z, plus one coat flat alkyd F, green

7 7 Hardboard Z, plus two coats flat alkyd F , green

7 8 Hardboard Z, plus one coat flat alkyd F and one coat gloss alkyd L

Particleboard A, 0. 500 in aspen poplar flakes, u r e a r e s i n binder, 36.8 pcf Particleboard A, plus one coat flat alkyd F , green

Particleboard A, plus one coat flat alkyd F and one coat gloss alkyd L , g r e e n Particleboard B, 0.625 in. aspen flakes, phenolic binder, 40.6 pcf

Particleboard B, plus one coat flat alkyd F , green

Particleboard B, plus one coat flat alkyd F and one coat gloss alkyd L, g r e e n

Particleboard R, 0.500 in., mixed hard and softwood chips, u r e a resin, 44.6 pcf ( s e e Sample 46, Table LIB)

Particleboard R, plus two coats flat alkyd F, g r e e n Fibreboard J , nom. 7/16 in. 17.2 pcf, unfinished

Fibreboard ceiling tile J , 12 x 12 x $ in. plain, white decorative finish

Fibreboard ceiling tile J, plus r o l l e r coat of intumescent latex paint Q (300 s q ft/gal) Fibreboard ceiling tile JR, 12 x 12 x $, "Random" acoustic drilling, white decorative finish Fibreboard ceiling tile JR, plus r o l l e r coat of intumescent latex paint Q (300 sq ft/gal) Fibreboard ceiling tile T, 12 x 12 x f in., plain white decorative finish

Fibreboard ceiling tile T, plus r o l l e r coat of intumescent latex paint Q (300 s q ft/gal)

Fibreboard ceiling tile TR, 12 x 12 x $ in. "Random" acoustic drilling, white decorative finish Fibreboard ceiling tile TR, plus r o l l e r coat of intumescent latex paint Q (300 sq ft/gal)

+

Standard substrate f o r testing f i r e retardant paints for i n t e r i o r combustible surfaces.

**

All ceiling t i l e s (i. e. Nos. 88 t o 95) w e r e mounted on 3/4 x 1 5/8-in. Douglas f i r framing in accordance with Appendix A1

.

,

ASTM E 84-68.

TABLE IIIB

COMPARISON OF FLAME SPREAD TESTS

S a m ~ l e E 162 Radiant Panel T e s t Pittsburgh Corning E 84 Tunnel Furnace R e m a r k s

NO. Q Is1 I s 2 I s 3 30/30 Apparatus- FSC FC SD IT,

FSR sec. over over over over over over over over over over cf. s a m p l e s 4 3 to 45. Table IIB Douglas f i r l u m b e r Hardboard Y Hardboard Z P a r t i c l e b o a r d A P a r t i c l e b o a r d B P a r t i c l e b o a r d R F i b r e b o a r d J Tile J F i r e - r e t a r d a n t paint Tile J R F i r e - r e t a r d a n t paint Tile T F i r e - r e t a r d a n t paint Tile T R F i r e - r e t a r d a n t paint

Figure 2

-

Pittsburgh Corning apparatus with flow meter and typical sample.

Figure 3

-

Top view of Pittsburgh Corning apparatus showing burner, viewing port, and light.

Figure 4

-

DBR tunnel furnace f r o m vent end. A: photocell and lamp assembly f o r smoke measurement; B: instrument panel and

controls; C: pyrometer for measuring floor temperatures.

Figure 5 Close -up of tunnel furnace. A: cover; B: port f o r measuring a i r velocity.

e Figure

6

-

Radiant panel apparatus.

A A: sample and holder;

B: stack,

"4

_--

_, -- ..--

Figure 7

-

Radiant panel apparatus.

A: the radiant panel; I

B: switches for timing I I

PANELS

-

4

'

X

8 '

E 162 SAMPLES

-

6

X

18

I/*"

PITTSBURGH CORNING SAMPLES (C)

-

4

5/gW

X

2g5/8"

FIGURE

8

SAMPLING P L A N

APPENDIX A

Calculations f o r the Pittsburgh Corning 30/30 T e s t Samples conditioned a t 48 t o 52 p e r cent

R.H.,

68 to 70 deg F.

Propane flow t o F i s h e r 3-902P B u r n e r

-

-

1050 cc/min (90 ~ t u / m i n ) F l a m e spread on $-in. asbestos-cement board: 3 in. (blank)

Calibration: Sample No. 38

Time, s e c 3/4-in. kiln-dried

z-in.

I f i r plywood, r e d oak (7.0% M. C. ) Lot

D

F l a m e Travel, in. 20 40 6 0 80 100 120 140 160 180 200 220 240

Avg. max. flame s p r e a d F l a m e No. FSR (by definition) (Coefficient

=

9 7 11 12.5 1 3 14 15. 5 15 16. 5 16.5 18 17.5 18.5 19 18.5 19 19.5 19.5 19 20.5 18 20.5 18.5 20.5 19.0 20.5 16.0 17.5 112 123 Average 117

APPENDIX B

1

Calculations f o r E 84 Tunnel T e s t on Sample No. 38, ,-in.

Fir Plywood, Lot D, and o t h e r C a s e s Sample conditioned a t 4070 R. H.

,

73 t o 75 deg F

G a s flow r a t e

=

4.399 s c f m

=

4408 ~ t u / m i n . , c o r r e c t e d f o r b a r o m e t r i c p r e s s u r e

Initial floor temps. : 105 and 95 deg F (14. 5 and 24-ft points) F i n a l floor temps: 340 and 298 deg F. Max t e m p (10-min. m a r k ) :

-1250 deg

F

Ignition time: 64 s e c F l a m e spread: 5 ft a t 1.50 rnin 8 ft a t 1.80 rnin 11 ft a t 2.30 rnin 1 3 f t a t 2. 50 rnin 1 5 ft a t 3.00 rnin 16 ft a t 4.25 rnin Visual end point: 4.50 rnin T i m e t o 980 deg F: 3.88 rnin

Equivalent r e d oak time: 5.3 5 rnin 53 5 T h e r e f o r e FSC

=

-

=

119 4.50

-

F u e l Contributed (75 d e ~ F b a s e line) A r e a under t e m p e r a t u r e c u r v e 32.40 sq in. A r e a , blank fuel c u r v e

Net a r e a , $-in. f i r plywood

Net a r e a , r e d oak flooring 14.10

1710

-

121 F C (fuel contributed)

=

-

-

14.10

Smoke Densitv A r e a under smoke c u r v e

Blank c o r r e c t i o n (1 0-min. run) 1

Net a r e a , z-in. f i r plywood Net a r e a , r e d oak flooring

3.01 sq in. 0.45

-

2. 56 6.40 2 5 6 SD (smoke density)

=

-

= 40 6.40

-

Other Cases (flame s ~ r e a d )

(1) F o r m a t e r i a l s on which the flame spreads 19$ ft in m o r e than 5$ but not m o r e than 10 min.

,

the flame -spread classification shall be 100 t i m e s 5Q min. divided by the time, t, that the

1

flame spreads 19; f t plus the difference of 100 minus this result, i. e.

,

FSC

=

50

+

275/t.

(2) F o r m a t e r i a l s on which the flame spreads l e s s than 19$ ft and then c e a s e s t o advance, o r recedes, in a 10-min. t e s t period:

(a) when the extreme flame distance, d, i s m o r e than 13$ f t

and l e s s than 195 ft the classification shall be 100 t i m e s 51 min t i m e s the distance, d, divided by 19; ft t i m e s 10 min.

,

plus

i

the difference of 100 minus this result, i. e.

,

FSC

=

50

+

1.41 d

(b) When the extreme flame distance, d, i s 1 3 i ft o r l e s s the classification shall be 100 t i m e s the distance d divided by 194 ft, i.e.

APPENDIX

C

Calculations f o r the Radiant Panel T e s t on Sample 38,

_-

Specimen 1-D of $-in. Fir Plywood, Lot D.

Sample conditioned a t 48 to 52 per cent R. H., 68 t o 70 deg

F.

T i m e s to reach successive 3-in. marks: t3 = 0.732 min.

t,

=

1.191

=

1.675 t12

=

2.490 tl,

=

4.006

Maximum temperature attained in stack: 319 deg C

Base temperature with asbestos-cement board: 202 deg C.

Isl =

Fs.Q

=

138.1

Is, =

143.1

Is, =

134.2

Averages for four specimens:

IS1 =

130.2 Is, = 133.0