Publisher’s version / Version de l'éditeur:
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la
première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
Internal Report (National Research Council of Canada. Division of Building
Research), 1963-05-01
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
NRC Publications Archive Record / Notice des Archives des publications du CNRC :
https://nrc-publications.canada.ca/eng/view/object/?id=b691cbb1-aeb8-4397-b97d-c4611c0fd4e2 https://publications-cnrc.canada.ca/fra/voir/objet/?id=b691cbb1-aeb8-4397-b97d-c4611c0fd4e2
NRC Publications Archive
Archives des publications du CNRC
For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.
https://doi.org/10.4224/20337881
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Forest fire retardants
NATIONAL RESEARCIi COUNCIL CANADA
DIVISION O F BUILDING RESEARCH
F O R E S T F I R E RETARDANTS b y K. S u m i
ANALYZED
I n t e r n a l R e p o r t No. 2 7 4 of t h e Division of B u i l d i n g R e s e a r c h OTTAWA M a y 1963P R E F A C E
T h e F i r e R e s e a r c h Section of the Division of Building R e s e a r c h in 1959 began studies of the u s e of r e t a r d a n t s and
s u p p r e s s a n t s for f o r e s t f i r e control. T h e s e studies w e r e under
-
taken following a r e q u e s t f r o m the Associate Committee on F o r e s t F i r e P r o t e c t i o n on which provincial and f e d e r a l f o r e s t r y agencies a r e r e p r e s e n t e d .T h e r a n g e of p o s s i b l e s t u d i e s i s broad. T h o s e m a d e t o date and now r e p o r t e d have been l a r g e l y exploratory, involving consideration of the gener a1 p r o b l e m , examination of l a b o r a t o r y evaluation p r o c e d u r e s and investigation of one type of r e t a r d a n t .
T h e author, a c h e m i c a l engineer, is a r e s e a r c h o f f i c e r with t h e F i r e R e s e a r c h Section, having r e s p o n s i b i l i t y f o r work on f i r e extinguishment.
Ottawa, May 1963
N. B. Hutcheon, Assistant Director.
FOREST F I R E RETARDANTS by
K. Sumi
The Division of Building R e s e a r c h of the National R e s e a r c h Council commenced studies in 1959 concerning the development of effective r e t a r d a n t s and s u p p r e s s a n t s for u s e in f o r e s t f i r e control. T h e s e studies w e r e undertaken following a r e q u e s t f r o m the A s s o c i a t e Committee on F o r e s t F i r e P r o t e c t i o n of the National R e s e a r c h Council that indicated potential u s e s for which new r e t a r d a n t s and s u p p r e s s a n t s
should b e considered:
( 1 ) t o r e t a r d t h e p r o g r e s s of f i r e by p r e p a r i n g f i r e l i n e s a t s o m e distance in advance of a f o r e s t f i r e ;
( 2 ) t o extinguish f i r e by d i r e c t application on a f i r e f r o n t ; and
( 3 ) t o p r o t e c t "high-value" a r e a s by making t h e s e a r e a s l e s s susceptible t o ignition.
( 1 ) . F i r e r e t a r d a n t and f i r e s u p p r e s s a n t a r e defined a s follows
.
A " r e t a r d a n t 1 ' i s used t o t r e a t t h e fuels at o r ahead of the f l a m e front s o that the combustion p r o c e s s i s 'modified when f i r e r e a c h e s the t r e a t e d fuel.A " s u p p r e s s a n t t t i s used t o extinguish the flaming or glowing p h a s e s of combustion by d i r e c t application t o t h e burning fuel.
R e t a r d a n t s a r e r e q u i r e d for the p r e p a r a t i o n of f i r e l i n e s and t r e a t m e n t of high-value a r e a s , and s u p p r e s s a n t s a r e r e q u i r e d for d i r e c t application on a f i r e front. An agent e f f e c t i v e a s both a r e t a r d a n t and a s u p p r e s s a n t would b e ideal.
T h e initial investigation was limited to r e t a r d a n t s . A review of l i t e r a t u r e on r e t a r d a n t s , the development of a l a b o r a t o r y t e s t , and experimental w o r k dealing with one type of r e t a r d a n t for possible u s e in f o r e s t f i r e control a r e described.
SCOPE OF THE PRESENT INVESTIGATION
The s i z e of a f i r e , the density, m o i s t u r e content, a r r a n g e m e n t of available fuel, and wind and weather conditions a l l a f f e c t the p r o g r e s s of a f i r e . In addition, t h e s u p p r e s s i o n methods employed, t h e s i z e of the fire-fighting c r e w and t h e equipment available to t h e m a r e governing f a c t o r s ,
B e c a u s e t h e r e a r e s o m a n y v a r i a b l e s that can influence the p r o g r e s s of a f o r e s t f i r e i t w a s decided t o l i m i t t h e scope of the p r e s e n t investigation t o the examination of a potential r e t a r d a n t f o r a specific f o r e s t situation. T h e conditions under which the new r e t a r d a n t s w e r e examined a r e given below.
T h e F i r e
The f i r e to be considered is a s m a l l s u r f a c e f i r e , defined a s "a f i r e that b u r n s s u r f a c e l i t t e r , other l o o s e d e b r i s of the f o r e s t f l o o r , and s m a l l vegetation. "(2) T h e c r e w available for extinguishing the f i r e or r e t a r d i n g i t s s p r e a d i s s m a l l , and l a r g e m e c h a n i c a l equipment i s not available.
T h e F o r e s t F l o o r
T h e depth of fuel on t h e f o r e s t floor i s not g r e a t , and a ground f i r e below the r e t a r d a n t is not, t h e r e f o r e , a s e r i o u s p r o b l e m . Ground f i r e is defined a s "a f i r e t h a t c o n s u m e s the o r g a n i c m a t e r i a l beneath t h e s u r f a c e l i t t e r of the f o r e s t floor. "(2) T h i s limitation was imposed b e c a u s e t h e r e l a t i v e effectiveness of different t y p e s of
r e t a r d a n t s i s dependent on the depth of fuel. Specific P u r p o s e of the Agent
The potential u s e of an agent a s a r e t a r d a n t for t h e p r e p a r a t i o n of f i r e l i n e s should b e considered.
The m o s t common method of p r e p a r i n g a f i r e line i s t o r e m o v e all fuel in advance of the f i r e in o r d e r t o b r e a k the fuel continuity in the f o r e s t . In constructing a f i r e line a c r e w will cut bushes, s m a l l t r e e s and logs along a given line, and dig o r r e m o v e
s u r f a c e l i t t e r alorig a s t r i p a foot o r m o r e in width down to m i n e r a l soil. Water o r r e t a r d a n t s , when available, can be used a s an
a l t e r n a t i v e method of p r e p a r i n g a f i r e line o r in conjunction with t h e method described. Hand tools a r e widely used f o r the p r e p a r a t i o n of f i r e l i n e s b e c a u s e l a r g e m e c h a n i c a l equipment such a s plows and b u l l d o z e r s a r e often not available. It i s under such c i r c u m s t a n c e s that t h e potential u s e of r e t a r d a n t s o f f e r s s o m e p r o m i s e .
LITERATURE R E VIEW
a subject of r e s e a r c h f o r over 100 y e a r s ( 1 ) , although t h e i r application to f o r e s t f i r e control did not r e c e i v e a g r e a t deal of attention until r e l a t i v e l y recently.
Since 193 1, however, the
U.
S. F o r e s t S e r v i c e h a s been engaged in l a b o r a t o r y and field s t u d i e s to examine the potential u s e of v a r i o u s c h e m i c a l s for f i r e suppression. Chemicals that have beenexamined include potassium c a r b o n a t e , calcium chloride, monoammonium phosphate, diammonium phosphate, l i m e , t a l c , c e m e n t , wetting
agents, sodium calcium b o r a t e and bentonite.
Use of new agents against actual f i r e s i s s t i l l v e r y limited. T h e r e a r e v a r i o u s r e a s o n s for t h i s :
( 1 ) t h e cost of c h e m i c a l s and t h e expense of t r a n s p o r t i n g them, ( 2 ) t h e difficulties encountered in handling c h e m i c a l s and using
new agents with conventional equipment, and
( 3 ) t h e r e l a t i v e l y s m a l l difference in effectiveness of t h e new agents a s compared with water alone.
Water i s a good s u p p r e s s a n t and a u s e f u l r e t a r d a n t , but for f o r e s t f i r e control i t h a s c e r t a i n limitations; i t s effect a s a r e t a r d a n t for t h e p r e p a r a t i o n of f i r e l i n e s i s only t e m p o r a r y , and i t is u s u a l l y needed in l a r g e quantities for extinguishing f o r e s t f i r e s . T h i s need for l a r g e quantities of water i s often a s e r i o u s p r o b l e m , b e c a u s e water is not always r e a d i l y , available in m a n y f o r e s t locations.
T h e s e a r c h , t h e r e f o r e , for new r e t a r d a n t s m o r e p e r s i s t e n t than w a t e r and for s u p p r e s s a n t s that will put out m o r e f i r e p e r unit of weight h a s been receiving i n c r e a s i n g attention in r e c e n t y e a r s .
Developments in this field include t h e u s e of a v i s c o s i t y additive t o i m p r o v e t h e f i r e fighting c h a r a c t e r i s t i c s of w a t e r , and the u s e of a gel of alginate ( e x t r a c t e d f r o m seaweed) and calcium chloride
a s a r e t a r d a n t . I n t e r e s t in a s u p p r e s s a n t that contains a v i s c o s i t y additive r e s u l t s l a r g e l y f r o m s t u d i e s c a r r i e d out by Grove and h i s a s s o c i a t e s at the S y r a c u s e University R e s e a r c h I n ~ t i t u t e ' ~ ) . T h e u s e of diammonium phosphate solution thickened with a v i s c o s i t y additive is at p r e s e n t receiving s o m e consideration for potential u s e a s both a r e t a r d a n t and a s u p p r e s s a n t . Various t h e o r i e s have been advanced in a t t e m p t s t o explain t h e behaviour of different t y p e s of r e t a r d a n t s on t h e combustion of wood(4); but b e c a u s e of t h e l a c k of e x p e r i m e n t a l work to e s t a b l i s h p r o p e r l y the validity of t h e s e t h e o r i e s , the m e c h a n i s m of the influence of r e t a r d a n t s ' i s highly speculative.
T h e behaviour of s e v e r a l different types of r e t a r d a n t s i s d i s c u s s e d below in the light of p r e s e n t knowledge:
1. ) T r e a t m e n t with c h e m i c a l s that m e l t at s o m e elevated t e m p e r a t u r e and coat t h e combustible m a t e r i a l with a liquid o r g l a s s y l a y e r .
-
T h e m e c h a n i s m of the effect of this type of r e t a r d a n t i s believed t o b e prevention of t h e e s c a p e of volatile combustion products f r o m the woodand any a c c e s s of oxygen t o the wood. Mixtures of b o r a x and b o r i c acid a r e considered to a c t in t h i s way.
2.
) T r e a t m e n t with chemicals t h a t i n t u m e s c e , i. e. f o r m f o a m s stable a t elevated t e m p e r a t u r e s .-
T h i s m e c h a n i s m i s s i m i l a r t o thep r e c e d i n g example. M a t e r i a l s that i n t u m e s c e m a y b e m o r e effective than g l a z e s ; the foam s e r v e s a s a b a r r i e r t o a i r and f l a m e and
provides t h e r m a l insulation. F i r e r e t a r d a n t paints that i n t u m e s c e with heat a r e considered to a c t in t h i s way.
3. ) T r e a t m e n t with c h e m i c a l s t h a t decompose o r change s t a t e t o a b s o r b enough heat t o prevent t h e combustible m a t e r i a l f r o m r e a c h i n g ignition t e m p e r a t u r e .
-
Water a c t s in this way. Few s u b s t a n c e s have endothermic h e a t s of t r a n s i t i o n o r of decomposition c o m p a r a b l e t o the heat ofvaporization of w a t e r . P r o t e c t i o n i s a t b e s t t e m p o r a r y , b e c a u s e
exhaustion of the supply of water l e a v e s t h e wood subject to combustion a s before.
4. ) T r e a t m e n t with r e t a r d a n t s t h a t m a y dilute the combustible g a s e s
sufficiently to r e n d e r the m i x t u r e non -flammable in a i r .
-
G a s e s considered effective diluents a r e water vapour and carbon dioxide. 5. ) T h e u s e of chain-br eaking inhibitors.-
A r e c e n t t h e o r y s u g g e s t s t h a t inhibition of flaming of the gaseous products could b e due to the influence of a suitable gaseous c a t a l y s t r e l e a s e d by decomposition of t h e r e t a r d a n t . T h e c a t a l y s t s usually considered a r e halogens and halogenated hydrocarbons.6. ) The influence of r e t a r d a n t s t h a t chemically affect the combustion of solid fuels.
-
Effective f i r e r e t a r d a n t s a r e believed t o a l t e r t h e decomposition r e a c t i o n s ( o r r a t e s of r e a c t i o n ) o c c u r r i n g in the solid ( 5 )7. ) T h e influence of c h e m i c a l s on glow r e t a r d a n c e .
-
Various t h e o r i e s have been advanced in a t t e m p t s t o explain this phenomenon. L a b o r a t o r ystudies a t the
U.
S. F o r e s t P r o d u c t s L a b o r a t o r i e s have indicated that ammonium phosphates and phosphoric acid a r e effective against both flaming and glowing.Discussion
A r e v i e w of l i t e r a t u r e indicated that it would b e advisable to l i m i t the p r e s e n t investigation t o one of the seven t y p e s of r e t a r d a n t s d i s c u s s e d above. It was decided to examine c h e m i c a l s that i n t u m e s c e o r puff up on exposure to h e a t o r f l a m e in o r d e r t o c r e a t e an insulating l a y e r over t h e m a t e r i a l to be p r o t e c t e d . Intumescent paints a r e
known t o b e effective in r e t a r d i n g s u r f a c e s p r e a d of f l a m e (when applied t o building m a t e r i a l s ) , but t h e potential u s e of this type of r e t a r d a n t f o r f o r e s t f i r e c o n t r o l does not appear t o have been given sufficient consideration.
Knowledge of formulations of intumescent paints i s available in the l i t e r a t u r e , but paints a r e expensive for u s e solely a s r e t a r d a n t s for f o r e s t f i r e control. Additives that produce good paint c h a r a c t e r i s t i c s a r e not n e c e s s a r y for the p u r p o s e under
consider ation, and t h i s investigation will b e directed t o w a r d s developing v a r i o u s f o r m u l a t i o n s of c h e m i c a l s that produce a s i m i l a r intumescent effect and in a s s e s s i n g t h e i r potential a s f i r e r e t a r d a n t s .
DEVELOPMENT O F TEST PROCEDURE
E a r l y in the investigation i t b e c a m e obvious that a l a b o r a t o r y t e s t would be d e s i r a b l e for s c r eenin.g p o s s i b l e f i r e r e t a r d a n t s ,
although field e x p e r i m e n t s would b e n e c e s s a r y for final a s s e s s m e n t . Such f a c t o r s a s uniformity of fuel bed, m o i s t u r e content of fuel and direction and speed of wind a r e b e s t controlled in t h e labor ator y.
T h e i d e a l t e s t would be s i m p l e , would yield r e l i a b l e r e s u l t s , differentiate the r e l a t i v e effectiveness of v a r i o u s r e t a r d a n t s and, if p o s s i b l e , s i m u l a t e the manner in which a r e t a r d a n t could be used under f o r e s t conditions.
T e s t Using P i n e Needles
T h e f i r s t method used pine n e e d l e s t o s i m u l a t e t h e f o r e s t floor. About 1, 500 gm of needles w e r e placed on a s b e s t o s cement board
1 ft by 3 ft. T h r e e different v a r i a t i o n s of this t e s t w e r e examined in o r d e r to e s t a b l i s h conditions that would e n s u r e s p r e a d of f i r e f r o m one end of the bed t o t h e other. F i r s t , the bed was inclined approximately 5 t o 20 deg and t h e needles w e r e ignited a t the bottom of the inclined plane. T h i s technique was used t o s i m u l a t e t h e effect of wind.
Second, t h e bed of needles w a s placed horizontally and a i r was blown over it f r o m one end. T h e f i r e w a s ignited a t the l e e w a r d end s o that
t h e m o v e m e n t of a i r (about 1, 0 0 0 ft p e r m i n ) would s p r e a d t h e f i r e t o t h e o p p o s i t e end. T h i r d , t h e bed of n e e d l e s w a s l e f t h o r i z o n t a l and a given quantity of h e p t a n e w a s b u r n e d in a t a n k a d j a c e n t t o one end of t h e bed of n e e d l e s . T h e f i r e s p r e a d f r o m t h e end a d j a c e n t t o t h e t a n k of h e p t a n e t o the o p p o s i t e end.
A m e a s u r e d a m o u n t of r e t a r d a n t w a s p l a c e d on 1 s q ft of t h e b e d of n e e d l e s e q u i d i s t a n t f r o m t h e e n d s in o r d e r t o e x a m i n e t h e s u i t a b i l i t y of t h e t e s t p r o c e d u r e with t h e v a r i a t i o n s r e p o r t e d above. S u i t a b i l i t y w a s judged on t h e b a s i s of r e p r o d u c i b i l i t y of d u p l i c a t e t e s t s and t h e a b i l i t y of the m e t h o d t o a s s e s s the e f f e c t i v e n e s s of
d i f f e r e n t r e t a r d a n t s in r e d u c i n g t h e s p r e a d of f i r e . T h e t i m e r e q u i r e d f o r f i r e t o a d v a n c e t o d i f f e r e n t p o s i t i o n s of t h e bed of n e e d l e s w a s r e c o r d e d f o r u s e i n a s s e s s i n g e f f e c t i v e n e s s . T h e r e t a r d a n t s u s e d t o e x a m i n e t h e s u i t a b i l i t y of t h e t e s t m e t h o d included w a t e r , a wetting a g e n t solution and bentonite s l u r r y .
R e l i a b i l i t y of d u p l i c a t e t e s t s w a s p o o r . In g e n e r a l , f i r e s p r e a d by b u r n i n g t h e n e e d l e s b e n e a t h a r e t a r d a n t , i n d i c a t i n g t h a t the d e g r e e of c o m p a c t i o n of t h e n e e d l e s influenced t h e r e s u l t s m u c h m o r e than t h e n a t u r e of t h e r e t a r d a n t . T h u s , t h e u s e of p i n e n e e d l e s t o s i m u l a t e t h e f o r e s t f l o o r w a s r e j e c t e d . T e s t Using Wood F i b r e b o a r d A s e c o n d method f o r a s s e s s i n g t h e r e l a t i v e e f f e c t i v e n e s s of r e t a r d a n t s w a s d e v i s e d . A c o m b u s t i b l e m a t e r i a l with s m a l l v a r i a t i o n s i n d e n s i t y w a s c o v e r e d with r e t a r d a n t p r i o r t o a t e s t . T h i s c h a n g e w a s m a d e i n o r d e r t o o v e r c o m e t h e p r o b l e m r e s u l t i n g f r o m v a r i a t i o n s in c o m p a c t i o n of p i n e n e e d l e s . Wood f i b r e b o a r d w a s s e l e c t e d and p l a c e d i n a h o r i z o n t a l p o s i t i o n s o that t h e r e t a r d a n t would b e u n i f o r m d u r i n g t h e t e s t . A given quantity of h e p t a n e w a s b u r n e d a d j a c e n t t o t h e s u b s t r a t e m a t e r i a l t o e n s u r e s p r e a d of f l a m e in t h e a b s e n c e of a r e t a r d a n t . T h i s t e c h n i q u e i s s i m p l e r t h a n t h e a l t e r n a t i v e t e c h n i q u e of blowing a i r o v e r t h e s u b s t r a t e m a t e r i a l d u r i n g a t e s t .
T h e t e s t w a s s e t up a s shown in F i g u r e 1. One and a h a l f g a l l o n s of h e p t a n e w e r e f l o a t e d on w a t e r in a f i r e t a n k m e a s u r i n g
2 b y 2 b y 1 ft deep. A m e a s u r e d quantity of f i r e r e t a r d a n t , g e n e r a l l y i n t h e f o r m of an a q u e o u s solution o r s u s p e n s i o n , w a s a p p l i e d a s e v e n l y a s p o s s i b l e on t h e wood f i b r e b o a r d . Heptane w a s ignited and allowed t o burn. As soon a s i t had b e e n c o m p l e t e l y c o n s u m e d t h e f i r e on t h e wood f i b r e b o a r d w a s e x t i n g u i s h e d with w a t e r . T h e r e t a r d a n t w a s then
s c r a p e d off t h e wood f i b r e b o a r d , i f n e c e s s a r y , t o d e t e r m i n e t h e length of c h a r f r o m t h e e d g e n e a r e s t t h e f i r e tank. Length of c h a r w a s u s e d
a s an index of the r e l a t i v e e f f e c t i v e n e s s of a r e t a r d a n t and w a s u s e d t o e x a m i n e whether it p r o v i d e s a m e a n s for a s s e s s i n g r e l a t i v e e f f e c t i v e n e s s of r e t a r d a n t s and y i e l d s c o n s i s t e n t r e s u l t s in r e p e a t e d t e s t s .
R e t a r d a n t s u s e d t o e x a m i n e t h e suitability of t h e t e s t p r o c e d u r e included w a t e r , bentonite s l u r r y , sodium c a l c i u m b o r a t e s l u r r y , a
wetting agent solution, a v i s c o s i t y additive in w a t e r , a m m o n i u m
phosphate solutions, "ABC" t y p e d r y c h e m i c a l extinguishing a g e n t s and a f i r e r e t a r d a n t paint of t h e i n t u m e s c e n t type.
T h e r e s u l t s indicated that t h i s t e s t method i s not sufficiently r e f i n e d for c l a s s i f y i n g f i r e r e t a r d a n t f o r m u l a t i o n s i n t h e i r o r d e r of effectiveness. It i s of a qualitative n a t u r e and a p p e a r s u s e f u l , however, in distinguishing v e r y good and v e r y poor r e t a r d a n t s , a s t h e s e
e x t r e m e s yield good r e p e a t a b i l i t y . In view of t h e r e l i a b i l i t y of r e s u l t s f o r e f f e c t i v e r e t a r d a n t s , t h e t e s t shows s o m e p r o m i s e f o r examining s m a l l d i f f e r e n c e s i n e f f e c t i v e n e s s of t h e s e r e t a r d a n t s . It w a s , t h e r e f o r e , decided t o conduct a s e r i e s of l a b o r a t o r y t e s t s on r e t a r d a n t s a f t e r m i n o r modifications t o the t e s t method.
DEVELOPMENT O F FLRE RETARDANT FORMULATIONS
Studies d i r e c t e d t o w a r d s t h e development of f i r e r e t a r d a n t s of t h e int-umescent type w e r e undertaken. A l a b o r a t o r y t e s t , e s s e n t i a l l y t h e s a m e a s t h a t developed and r e p o r t e d in the p r e v i o u s s e c t i o n ,
w a s s e l e c t e d for s c r e e n i n g out p r o m i s i n g r e t a r d a n t s and examining the effect of modifying t h e f o r m u l a t i o n s . In corljunction with t h i s w o r k a n u m b e r of m a t e r i a l s o r f o r m u l a t i o n s that have b e e n c o n s i d e r e d a s r e t a r d a n t s o r s u p p r e s s a n t s f o r f o r e s t f i r e c o n t r o l w e r e examined, u s i n g t h e s a m e technique i n o r d e r t o obtain s o m e i d e a of the r e l a t i v e e f f e c t i v e n e s s of t h e new f o r m u l a t i o n s .
A t y p i c a l i n t u m e s c e n t f i r e r e t a r d a n t m i x t u r e contains 1. ) a blowing agent, e. g. u r e a ,
2. ) a f i r e r e t a r d a n t s a l t , e. g. d i a m m o n i u m phosphate, and
3. ) a m a t e r i a l affected by blowing agent and i n t u m e s c e s , e. g. glucose.
Two t y p e s of i n t u m e s c e n t f o r m u l a t i o n s w e r e c o n s i d e r e d for t h e p r e s e n t investigation: a w a t e r solution and a d r y powder. It w a s thought that for t h e w a t e r solution type t h e c o n s t i t u e n t s of t h e
i n t u m e s c e n t f o r m u l a t i o n s , should, if p o s s i b l e , be s o l u b l e i n w a t e r . T h e application p r o b l e m i n the field would b e s i m p l e , b e c a u s e
equipment commonly used f o r application of water could be used. In addition, by attempting t o develop formulations that a r e r e l a t i v e l y dilute the coat of m a t e r i a l s could b e reduced. One of t h e r e q u i r e m e n t s of the d r y powder type a p p e a r s t o be an anti-caking p r o p e r t y , which i s i m p o r t a n t f o r t h e handling of the m a t e r i a l in the field r e g a r d l e s s of the method of application.
Method
The f i r e r e t a r d a n t t e s t w a s s e t up a s shown in F i g u r e 1. Two gallons of heptane w e r e floated on 2 in. of w a t e r in a f i r e tank m e a s u r i n g 2 by 2 by 1 ft deep. A p i e c e of wood f i b r e b o a r d , 24 by 15 b y 1/2 in. thick, w a s positioned horizontally adjacent t o one of t h e
s i d e s of t h e tank in such a m a n n e r that i t s upper s u r f a c e was a t the l e v e l of t h e top of the tank.
T h e f i r e r e t a r d a n t , generally in t h e f o r m of an aqueous solution o r suspension, was applied a s evenly a s p o s s i b l e over an a r e a 24 by 12 in.
,
leaving an unprotected s t r i p 24 by 3 in. along the edge of the wood f i b r e b o a r d f a r t h e s t f r o m the tank. T h e heptane was then ignited and allowed t o b u r n until completely consumed.One observation was made to d e t e r m i n e whether the r e t a r d a n t prevented ignition of the unprotected s t r i p of wood fibreboard. If i t did not
ignite a f u r t h e r examination was m a d e , a s follows: the f i r e on t h e s u b s t r a t e m a t e r i a l was extinguished with water a s soon a s the heptane was completely consumed. T h e r e t a r d a n t was then s c r a p e d off and the m e a n distance of c h a r on the wood f i b r e b o a r d , m e a s u r e d f r o m the edge of t h e f i r e tank, was determined. T h e mean d i s t a n c e of char w a s used a s t h e index for a s s e s s i n g t h e effectiveness of a r e t a r d a n t . R e t a r d a n t s
..-
T h e c h e m i c a l s w e r e mixed with 100 m l of w a t e r in the p r o p o r t i o n s given, except in the c a s e of two b r a n d s of d r y c h e m i c a l and one brand of f i r e r e t a r d a n t paint.
Non -intum escent formulations
1) Bentonite ( 5 p e r c e n t )
2) Alkanol WXN ( 1 p e r cent)
-
a wetting agent3 ) Sodium calcium b o r a t e (30 p e r cent)
4) Diammonium phosphate (12 p e r cent)
+
Alkanol WXN ( 1 p e r cent)5) Monoammonium phosphate (18 p e r cent)
+
Alkanol WXN ( 1 p e r cent)6 )
A c o m m e r c i a l ABC type powderI n t u m e s c e n t f o r m u l a t i o n s
T h e i n t u m e s c e n t f o r m u l a t i o n s w e r e developed b y t r i a l and e r r o r , and t h e quantity of c h e m i c a l s u s e d w a s k e p t s l i g h t l y above t h e m i n i m u m r e q u i r e d t o e n s u r e good i n t u m e s c e n c e in t h e p r e s e n t t e s t . 1) A c o m m e r c i a l f i r e r e t a r d a n t p a i n t (100 g m ) 2) U r e a (10 g m )
+
d i a m m o n i u m p h o s p h a t e (30 g m ) t c o r n s y r u p (50 g m ) 3) U r e a (10 g m ) t d i a m m o n i u m p h o s p h a t e (30 g m )+
s u g a r (60 g m ) 4) U r e a (10 g m ) t d i a m m o n i u m p h o s p h a t e (30 g m ) t s u g a r (60 g m )+
c a r b o x y m e t h y l c e l l u l o s e ( 2 g m ) 5) U r e a (10 g m )+
d i a m m o n i u m p h o s p h a t e (30 g m ) t s u g a r (60 g m )+
K e l t e x FF ( 2 g m ) 6 ) U r e a (10 g m ) t d i a m m o n i u m p h o s p h a t e (30 g m ) t s u g a r (60 g m )+
Alkanol WXN 7 ) D i c y a n d i a m i d e (10 g m ) t d i a m m o n i u m p h o s p h a t e (30 g m ) t s u g a r (60 g m ) 8 ) Glycine (10 g m )+
d i a m m o n i u m p h o s p h a t e (30 g m ) t s u g a r (60 g m ) F o r m u l a t i o n n u m b e r s 7 and 8 w e r e e x a m i n e d both in t h e d r y s t a t e and with 100 g m of w a t e r . F o r m u l a t i o n n u m b e r s 2, 3, 4, 5 and 6 w e r e of t h e w a t e r solution type. R E S U L T S AND DISCUSSION I n t u m e s c e n t f o r m u l a t i o n s , in g e n e r a l , a p p e a r e d t o b e m o r e e f f e c t i v e t h a n t h e o t h e r f o r m u l a t i o n s e x a m i n e d on t h e b a s i s of t h e p r e s e n t t e s t s . T h e m o s t e f f e c t i v e i n t u m e s c e n t f o r m u l a t i o n s a p p e a r e d t o b e n u m b e r s 1 and 4 of t h e w a t e r solution type and n u m b e r s 7 and 8 of t h e d r y p o w d e r type. In t h e ? r e s e n t e x p e r i m e n t s t h e quantity of r e t a r d a n t a p p l i e d o v e r a given a r e a w a s i n t e n t i o n a l l y k e p t t o a s m a l l a m o u n t i n o r d e r t o e x a g g e r a t e t h e d i f f e r e n c e s in t h e e f f e c t i v e n e s s of r e t a r d a n t s . Hence, t h e e x p e r i m e n t a l r e s u l t s should n o t b e c o n s t r u e d a s a p o s i t i v e method f o r s c r e e n i n g o t h e r p r o m i s i n g r e t a r d a n t s . T h e y a r e p r o b a b l y a p p l i e d i n g r e a t e r q u a n t i t y o v e r a given a r e a in t h e f i e l d t h a n w a s u s e d i n t h e p r e s e n t e x p e r i m e n t s ,The water solution type of intumescent formulation d i d not appear t o be a s e f f e c t i v e a s the d r y powder type, p r e s u m a b l y b e c a u s e of the choice of wood f i b r e b o a r d a s the s u b s t r a t e m a t e r i a l . Some
of the solution tended to p e n e t r a t e the wood f i b r e b o a r d , with the r e s u l t that intumescence was not a s pronounced a s with the powder type.
Substitution of s u g a r f o r c o r n s y r u p in a formulation appeared advantageous b e c a u s e sugar i s m o r e r e a d i l y soluble. T h e addition of 0. 5 p e r cent
of sodium carboxymethylcellulose ( C M C ) s e e m e d t o i m p r o v e t h e r e t a r d a n t , while a s i m i l a r addition of another v i s c o s i t y additive, Keltex F F , did not show such improvement. T h e addition of t h e wetting agent, Alkanol WXN, s e e m e d t o hinder intumescence.
In o r d e r t o d e t e r m i n e t h e ability of a w a t e r solution type
of r e t a r d a n t to i n t u m e s c e on loosely packed m a t e r i a l s a s i m p l e experiment w a s devised. T h e r e t a r d a n t was applied on a bed of pine needles and
f l a m e f r o m a Bunsen b u r n e r was directed on the r e t a r d a n t - t r e a t e d
fuel. T h e r e s u l t s indicated that t h e water solution type does not intumesce sufficiently, p r e s u m a b l y b e c a u s e the l o s s of solute into the fuel bed
i s too great. Solution type r e t a r d a n t s in which i n c r e a s i n g amounts of a viscosity additive w e r e p r e s e n t w e r e examined, but again the r e s u l t s w e r e not v e r y encouraging. T h e u s e , t h e r e f o r e , of t h i s type of
r e t a r d a n t for p r e p a r i n g f i r e l i n e s does not s e e m v e r y suitable on fuel beds such a s pine n e e d l e s , although t h e r e m a y b e other f o r e s t situations w h e r e i t would b e successful.
A d r y powder type of intumescent formulation was m o r e effective when applied t o a bed of pine needles. Its m a i n disadvantage i s t h e probable high cost of m a t e r i a l s , because a r e l a t i v e l y l a r g e
quantity of powder i s r e q u i r e d . Again, it m a y have potential u s e s under c e r t a i n f o r e s t conditions of which the author i s not a w a r e .
The formulation of u r e a , diammonium ~ h o s ~ h a t e and s u g a r \
produced a powder that s e e m e d t o b e hygroscopic. L a b o r a t o r y
examinations w e r e c a r r i e d out after grinding the c h e m i c a l s t o a p a r t i c l e s i z e r a n g e c o m p a r a b l e to that of d r y chemical extinguishing agents
on the m a r k e t . The caking tendency could not be controlled by m e r e addition of s m a l l quantities of a w a t e r r e p e l l a n t m a t e r i a l such a s zinc s t e a r a t e . T h e powder a l s o caked when subjected t o p r e s s u r e in a c o m m e r c i a l s t o r e d p r e s s u r e -type d r y chemical f i r e extinguisher
s o that a f t e r s t o r a g e t h e d i s c h a r g e c h a r a c t e r i s t i c s w e r e v e r y poor. Attempts w e r e m a d e t o r e d u c e the p r o b l e m c r e a t e d by the caking tendency of t h e c h e m i c a l s in the formulations. Other chemicals w e r e considered a s a l t e r n a t i v e s for both s u g a r and u r e a . None of the a l t e r n a t i v e s for s u g a r w a s c o n s i d e r e d s a t i s f a c t o r y , although both
dicyandiamide and glycine showed p r o m i s e a s s u b s t i t u t e m a t e r i a l s f o r the blowing agent, u r e a . Both s e e m e d t o b e l e s s h y g r o s c o p i c than u r e a .
T h e c o s t of a r e t a r d a n t o r a s u p p r e s s a n t m u s t b e c o n s i d e r e d with r e l a t i o n t o i t s e f f e c t i v e n e s s b e f o r e new a g e n t s c a n find s u p p o r t f o r wide u s e in f o r e s t f i r e control. An a t t e m p t will b e m a d e , t h e r e f o r e , t o give s o m e i d e a of the c o s t of t h e m a t e r i a l s involved.
T h e m a i n c o n s t i t u e n t s of one of the powder f o r m u l a t i o n s w e r e d i ~ ~ a n d i a m i d e , d i a m m o n i u m phosphate and icing s u g a r . T h e c o s t s of c h e m i c a l s w e r e :
Dic yandiamide 15 cents/lb
Diammonium phosphate 15 cents/lb
Icing s u g a r 12
-
1/2 c e n t s / l b F o r a powder f o r m u l a t i o n containing d i c y a n d i a m i d e : diammonium p h o s p h a t e : i c i n g s u g a r in a weight p r o p o r t i o n of 1 : 3 : 6t h e c o s t p e r pound of m i x t u r e would b e about 15 c e n t s . In t h e f i r e r e t a r d a n t t e s t s c a r r i e d out in the p r e s e n t investigation, a p p r o x i m a t e l y
100 gm of t h i s f o r m u l a t i o n p r o d u c e d a r e a s o n a b l y e f f e c t i v e i n t u m e s c e n t r e t a r d a n t f o r p r o t e c t i n g 2 s q ft. T h u s , t h e c o s t of c h e m i c a l s would b e a p p r o x i m a t e l y 1.6 c e n t s p e r s q ft o r $1.60 p e r 100 s q ft. Actual c o s t for u s e in the f o r e s t would be c o n s i d e r a b l y g r e a t e r , b e c a u s e t h e above calculation w a s based on l a b o r a t o r y e x p e r i m e n t s f o r which t h e powder w a s applied u n i f o r m l y on a flat h o r i z o n t a l s u r f a c e . Neither t h e c o s t of p r o d u c i n g t h e powder m i x t u r e n o r t h e p o s s i b l e inclusion of a n t i - c a k i n g and free-flowing a g e n t s w e r e c o n s i d e r e d . P r i c e s of c h e m i c a l s used in t h e calculation m a y riot h a v e b e e n t h e l o w e s t p o s s i b l e , but
t h i s d i f f e r e n c e m a y be s m a l l in r e l a t i o n t o production c o s t .
In t h e p r e s e n t l a b o r a t o r y s t u d i e s glycine a p p e a r e d t o b e the m o s t p r o m i s i n g of t h e blowing a g e n t s examined. T h e f o r m u l a t i o n in which glycine i s one of the c o n s t i t u e n t s was not u s e d in the c a l c u l a t i o n , h o w e v e r , b e c a u s e t h e p r i c e of t e c h n i c a l g r a d e glycine w a s not a v a i l a b l e t o t h e a u t h o r .
Two b r a n d s of ABC t w e d r y c h e m i c a l extinguishing a g e n t s , which have been on t h e m a r k e t f o r t h e p a s t few y e a r s , w e r e examined f o r potential u s e a s r e t a r d a n t s . T h i s t y p e of powder i s a r e c o g n i z e d u s e f u l s u p p r e s s a n t f o r extinguishing s m a l l C l a s s A f i r e s , defined a s f i r e s involving o r d i n a r y c o m b u s t i b l e m a t e r i a l s s u c h a s wood and p a p e r . T h e ABC t y p e of d r y c h e m i c a l which w a s examined did not s e e m t o
f o r m u l a t i o n s t h a t w e r e developed a p p e a r e d t o be s u p e r i o r a s r e t a r d a n t s t o t h e ABC t y p e p o w d e r s , a c c o r d i n g t o the t e s t s c a r r i e d out in t h e
p r e s e n t investigation. It i s believed t h a t e f f o r t s t o develop a n intumescent type d r y c h e m i c a l f o r u s e a s a s u p p r e s s a n t d e s e r v e s s e r i o u s c o n s i d e r a t i o n .
CONCLUSIONS AND RECOMMENDAT IONS
L a b o r a t o r y s t u d i e s t o date i n d i c a t e t h a t r e t a r d a n t s t h a t
i n t u m e s c e when s u b j e c t e d t o f i r e show p r o m i s e of p o t e n t i a l u s e i n f o r e s t f i r e control. T W O t y p e s of s u c h f o r m u l a t i o n s s u g g e s t e d for consideration a r e :
( a ) A w a t e r solution type, e. g . , a r e t a r d a n t c o n s i s t i n g of u r e a ,
diammonium phosphate, s u g a r and w a t e r . A thickening agent such a s sodium c a r b o x y m e t h y l c e l l u l o s e could b e added t o t h i s solution. ( b ) A powder type, e . g . , a r e t a r d a n t c o n s i s t i n g of glycine, diammonium
phosphate and s u g a r . Anti -caking and f r e e -flowing a g e n t s could b e added t o f a c i l i t a t e both handling and application.
T h e two t y p e s of f o r m u l a t i o n s s u g g e s t e d f o r c o n s i d e r a t i o n w e r e found t o b e m o r e effective a s r e t a r d a n t s under t h e conditions of t e s t d e s c r i b e d i n t h i s r e p o r t than t h e ABC t y p e of d r y c h e m i c a l a t p r e s e n t on t h e m a r k e t . T h e powder t y p e of f o r m u l a t i o n , i f developed a s a s u p p r e s s a n t , m i g h t a l s o have p o t e n t i a l u s e f o r s i t u a t i o n s other than f o r e s t f i r e control. ACKNOWLEDGEMENTS T h e author w i s h e s t o thank M e s s r s . C. W o l f g r a m , E .
11,
Mulligan and E . W. O r a c h e s k i f o r a s s i s t a n c e in t h e conduct of the e x p e r i m e n t a l work.R E F E R E N C E S
1. Wilson, C, C . , P a p e r p r e s e n t e d a t the Annual Meeting of t h e W e s t e r n F i r e R e s e a r c h C o m m i t t e e , V i c t o r i a , B. C.
,
D e c e m b e r 6, 1960. 2. Davis, K. F . , F o r e s t F i r e C o n t r o l and Use. McGraw-Hill, 1959,5 8 4 ~ . 3. G r o v e , C. S .
