Abstract-This paper presents observations on the toxicity of gases produced by materials under three different combustion conditions. The difficulty of the general problem of toxicity is emphasized and the impossibility-at the present stage in the research-of satisfying the increasing pressure to establish toxicity safety regulations is stated.
This paper presents results of tests performed on 35 materials, including woods, synthetic and textile materials, which have been submitted to thermal degradation at three different combustion temperatures. In addition, the interpretation and limitations of toxicological test results are discussed more generally. INTRODUCTION -~Although fire fighting techniques have greatly developed and improved over the years and although the way in which buildings are designed as well as the types of materials available to build them have undergone a rapid evolution, the problem of toxicity caused by the burning of building materials, including furniture and decorating elements, remains a very important one.Referring only to a small country like Belgium the list of fire disasters since 1955 is impressive: This leaves out of consideration the family home fires in which one or several people die, as was the case in Deurne in November 1977 where a mother and five children died, or in Herstal in May 1978, costing the lives of five people. The number of such losses every year is serious and although such fires have less impact on the public, they are very important as it has been found that the majority of toxicity victims are to be found in fires in dwellings and that two-thirds of the fatalities are met in the room where the fire started.1 These statistics indicate a rapid incapacitation in which the victims fail to make use of possible excape routes. These facts are relevant to the elaboration of a test method imitating as closely as possible the early stages of fire during which the toxicological hazards play the most important role. The need for a biological assessment of the toxic hazards of fire has become generally acknowledged, and in recent years a great deal of research has been accomplished along these lines in a number of countries including Belgium, Germany, France, Japan, UK, USA etc. It is beyond the scope of the present paper to make reference to the numerous publications which have recently appeared in an increasing number of new journals covering the topic of combustion toxicology.Due to the complexity of the fire situation there are many different approaches possible when trying to establish a procedure for a small-scale test which explains the number of different methods in use at present. They can, in fact be divided into two categories, both systems having advantages and disadvantages as follows :1. In the first category, the animals are placed directly in the degradation chamber2 which may raise problems such as heat stress, oxygen depletion etc. 2. In the second category, degradation of the sample takes place in one apparatus (a moving tube system being used in most of the European c~u n t r i e s~-~) and the effluent products are transferred, with or without dilution, to animal chambers. This raises the problem of the effect of transfer on the composition of the toxic atmosphere.As far as the animal evaluation is concerned, methods Methods of the first type seem preferable in relation to the problem of acu...
The combustion or pyrolysis of perfluorinated resins, under cer tain laboratory conditions (e.g., the "NIST" smoke toxicity test), produces fumes which are 2-3 orders of magnitude more toxic than the smoke from common plastics or wood. To determine whether these materials show the same high level of toxicity under realistic fire conditions, a series of twenty full-scale test burns was carried out at the facilities of the Laboratory for Heat Transfer and Fuel Technology, State University of Ghent, Belgium. A metal tray holding up to 30 kg of 25-pair telecommunications cable in sulated and jacketed with fluorinated materials (Teflon® FEP and/or Teflon® PFA) was exposed to fires involving 110 kg wood cribs, or energetically equiva lent amounts of diesel fuel or polyurethane foam. The burn facility was an 8' × 12' × 8' high (2.4 m × 3.7 m × 2.4 m) masonry room connected to a 43- foot (13 m) corridor. Smoke flowed out of the burn room, down the corridor, and into a smoke collection stack. Near the end of the corridor, a portion of the smoke was extracted, diluted and cooled, and passed through one of a series of stainless steel exposure chambers, each containing ten male Sprague-Dawley rats. Temperature and fuel weight loss were measured at regular time inter vals in the burn room, as were smoke temperature and composition (CO, CO2 and fluorine analysis), as it passed down the hallway and into the smoke collec tion stack. Carbon monoxide, oxygen, fluorine content and temperature of the smoke were also monitored in the animal exposure chambers. Fires were allowed to burn for 30-40 minutes. Animals were exposed to smoke for 30 minutes, after which the surviving animals were observed for a two-week post-exposure period. Selected animals were killed and tested for blood carboxyhemoglobin (COHb) content and tissue samples from the respira tory tract were subsequently examined for histopathological characteristics. Smoke reaching the end of the corridor contained only about one-third of the theoretical amount of fluorine. Additional losses were incurred during dilution and in the animal chamber. The fluorine loss is probably attributable to deposi tion of hydrogen fluoride in the high-humidity conditions associated with com bustion. The exposed animals showed some of the effects previously attributed to combustion products of fluoropolymers, but also showed near-lethal amounts of blood COHb, attributable to carbon monoxide from the principal fuel. Simi lar results were obtained whether the fire fuel was wood or diesel fuel. Use of polyurethane foam as a fuel was found to be unsuitable. The lethal smoke con centration of the cable smoke alone, i.e., without the effects of the carbon monoxide contributed by the principal fuel, is estimated to be 1.6 mg/l, or about 80 times less toxic than would be expected based on the NIST test. This toxicity is within a factor to two of what would be expected if the princi pal toxic agent (in addition to CO) were hydrogen fluoride or carbonyl fluoride. No evidence was found for the highly toxic agent present in the NIST test, which either did not form or existed only transiently in these experiments.
Fire retardants improve reaction to fire characteristics such as ignitability and flame propagation. This paper presents the toxicological results of tests performed on eleven pairs of untreated and treated materials, including woods, synthetic materials and textiles (both natural and synthetic). It is shown that the effects of fire retardants on toxicity results can be variable. In addition, the problem of the use of toxicity results is discussed more generally. INTRODUCTIONToxic effects are to be considered as a part of the general reaction to fire behaviour of a material including other characteristics such as ignitability, flamc propagation, rate of heat release, smoke opacity and corrosivity. All those properties of a material interact to determine the growth of a fire and the resulting damage to life and property.Fire retardant treatments make it possible to improve such characteristics as the ignitability and flame propagation of materials. From the safety point of view the effect of such treatments on the toxicity of the effluent thermal degradation products is also important. In a previous paper' comparison of four pairs of fire retardant and untreated woods and synthetic polymers led to the conclusion that all treated materials were more dangerous than the untreated ones, the difference being of varying degrees of importance. This raises a real problem: is it preferable that a product should flare and spread flames without producing too great amounts of toxic gases, or that the same product having been treated, should smoulder while producing more lethal gases?Since the testing of four pairs of materials does not provide sufficient evidence on which to base more general conclusions the present paper presents results on eleven pairs of materials tested in three different temperature conditions. Previous results at approximately 400", 600" and 800°C' have shown that for a majority of the thirty-five materials tested the temperature of approximately 600 "C was the most critical condition as far as toxicity is concerned. It was therefore decided to reduce the temperature interval and to perform this series of tests at approximately 500", 600" and 700 "C. METHODSThe biological testing method, using Wistar rats, has been described in previous paper^.^-^ It is a so-called MATERIALSThe tested materials are listed below with a reference indication for further presentation and discussion of the results. They include wood products (B), plastics (synthetic) (K) and textiles (both natural and synthetic) (T). Where possible, thickness of the sample in mm (d) and the density of the material in kgm-3 ( D ) are given. All samples had a length of 300mm and their weight is given in Table 1 and diammonium-hydrophosphate (NH4)2HP04, approximately 310 g mP2. T7 = Curtain fabric: 58% cotton; 42% fibranne, approximately 250 g m-2. T8 = T7, treated to become fire retardant with ammonium-salts and sodium-tetraborate or Borax (Na2B407.10H20), approximately 250 g mp2.(10.0 g wood; 1.1 to 1.4 g varnish).33). Table 2 gives an ide...
An attempt has been made to present toxicological results obtained by a biological evaluation method in a simple and comprehensive way. The calculation of a toxicity index which expresses mortality rates as a function of the very important time factor is proposed. Additionally it is shown how such an index could be used to rank a series of twenty materials according to their relative toxicity.
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