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ABSTRACTS AND R E V I E W S 241 since after this time i t is likely that the whole laboratory would be gutted I t is also desirable that any cupboard should be reasonable in cost and should fit m wi th normal laboratory furniture Steere, examimng chemical storage cabmets for fire protection, showed that heat transfer across cabmet walls constructed of 1-in -thick wood was relatively very poor for short periods and recommended such cabinets for the storage of flammable liqmds wi th the volumetric capacity limited to 50 f t ' The Institute of Animal Physiology, Babraham, Cambndge, and the Fire Re- search Station, Boreham Wood, collaborated m the development of a suitable wooden cupboard Two successive prototypes have been tested to destruction, and this note presents the results of an investigation to examine the performance of the second and final prototype in a spillage fire I t wi l l , of course, be necessary to ensure that such furniture satisfies legal requirements and those of any controlling bodies Wilde, D . G . (Safety m Mines Research Establishment, Sheffield, England) "Fire- Retardant Treatments for Mine Timber," The Mining Engineer 132, 281 (1972) Section: A Subjects: Fire retardants, Retardants, Mine timber, Timber, Wood, Roadways m mines, Testing of retardants, Pyrolysis, Testing methods, Coatings Author's Synopsis and Conclusions The maimer and extent of use of timber as a linmg for imne roadways has led to the adoption of some form of fire-retardant treatments i n appropriate cases Impregnated fire-retardant treatments for timber cause mcreased evolution of the nonflammable proportion of the volatile products when wood is decomposed by heat They also cause an increase in the proportion of charcoal that remains after the evolution of volatile products has ceased Fire-retardant surface coatings for timber reduce the heat that is transferred to wood from flames near the surface of the sohd, and inhibit the mixing of the flammable volatile products of decomposition wi th air Fire-retardant treatments can only be fu l ly proved in full-scale fire tnals, small- scale test are useful for "screemng" new formulations for treatments and provide a convement way of checking the quahty of accepted treatments A treatment should prevent timber from contnbuting significantly to the heat and fumes of a fire wi th a total output, varymg at times from 6 M W to 2 M W , m which temperatures m the fumes reach SOO^C, and which last, in all, for about one hour The impregnated treatment, that has virtually exclusive use among treatments of this type m British mines, can achieve such a performance There are a number of fire-retardant surface coatings that are similarly effective
242 F I R E R E S E A R C H No treatment can mdefimtely prevent the burmng of timber; a typical im- pregnated treatment has been shown to lose its effectiveness after twenty-mmutes' exposure to an exceptionally mtense fire Conclvsions 1 Timber hmngs of roadways are pecuharly susceptible to fire, because the wood IS contmuously distributed 2 The flammabihty of wood depends largely on the type of pyrolysis induced by heating Maximum flammabihty results when pyrolysis is rapid, and produces maximum evolution of tar vapour 3 There is evidence that impregnated fire-retardant treatment for wood modifies the chemical processes during pyrolysis of wood, to produce a slow endothermic pyrolysis This results m increased formation of char, which is retamed within the wood, and in enhanced evolution of incombustible gases and vapours 4 Fire-retardant surface coatings for mine timber are based on the prmciple of providing a practicable, stable barrier between wood and the atmosphere surrounding i t 5. As a basis for estabhshing testing methods, i t is suggested that a fire-retardant treatment for miiung timber should prevent, or greatly delay, the igmtion of timber by moderate sized locahzed sources wi th radiation mtensity of not less than 30 kW/m*, and a total output of not less than 10 k W A treatment should also halt, or control, spread of flame in timber exposed to a test fire w i t h an average output of about 2 M W , intermittent outputs of up to 6 M W , and m which timber is exposed to radiation ranging m mtensity up to 80 kW/m» 6. There is virtually only one impregnated fire-retardant treatment for use in Britain, the N C B product known as "Fyrprufe " The mixture is based on ammomum salts Full-scale fire trials have shown that "Fyrprufe" is an effective fire-retardant treatment, capable of controllmg the spread of a well- developed fire into a single layer of treated hardwood cover boards The treatment was also effective in controlhng the burmng of wood in intense fires lasting 3 and 12 minutes, respectively A n experiment carried out in Germany indicated, however, that an impregnated treatment, having the same character as "Fyrprufe," failed to protect timber from an exceptionally mtense fire after 20 minutes After prolonged exposure to fire, impregnated timber burns freely through a charcoal/air reaction 7 Fire-retardant surface coatings for mine timber have, unt i l recently, been based on sodium sihcate Such coatings can be effective, but there are practical problems associated wi th their use in mines that make i t difficult to apply them in a way that results in the desired performance 8 Commercial development of other materials, capable of retarding the igmtion and spread of fire, has ehrmnated many of the difficulties associated wi th sodium silicate coatings 9 Fire-retardant surface coatings exist that are based on polymers and inert filhngs, but they would probably not be admissible under the terms of N C B instructions govermng the combustibility of surface coatings Polymer materials may give rise to toxic fumes, in the event of their being exposed to a fire
