Toxic combustion products

Metal-fluorocarbon reactions yield fluorides and carbonaceous products as the main products, which can be potentially harmful to both humans and the environment. Thus, in the following sections, the formation and release of these materials 

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Acrylonitrile is combustible and ignites readily, producing toxic combustion products such as hydrogen cyanide, nitrogen oxides, and carbon monoxide. It forms explosive mixtures with air and must be handled in weU-ventilated areas and kept away from any source of ignition, since the vapor can spread to distant ignition sources and flash back. 

The use of fire retardants in polymers has become more complicated with the realisation that more deaths are probably caused by smoke and toxic combustion products than by fire itself. The suppression of a fire by the use of fire retardants may well result in smouldering and the production of smoke, rather than complete combustion with little smoke evolution. Furthermore, whilst complete combustion of organic materials leads to the formation of simple molecules such as CO2, H2O, N2, SO2 and hydrogen halides, incomplete combustion leads to the production of more complex and noxious materials as well as the simple structured but highly poisonous hydrogen cyanide and carbon monoxide. 

Elevated Flares See Flares for a general definition. The elevated flare, by the use of steam injection and effective tip design, operates as a smokeless combustion device. Flaring generally is of low luminosity up to about 20 % of maximum flaring load. Steam injection tends to introduce a source of noise to the operation, and a compromise between smoke elimination and noise is usually necessary. When adequately elevated (by means of a stack) this type of flare displays the best dispersion characteristics for malodorous and toxic combustion products. Visual and noise pollution often creates nuisance problems. Capital and operating costs tend to be high, and an appreciable plant area can be rendered unavailable for plant operations and equipment because of excessive radiant heat. 

Pollution Limitations - (i.e., smoke formation, malodorous or toxic combustion products, noise) which may be based on statutory and/or public relations requirements. 

Poisoning from toxic combustion products. In chemical fires, particularly those involving mixtures, an extremely complex mixture of gases and particulates, e.g. smoke may be produced. The composition depends upon the initial compounds involved, the temperatures attained and the oxygen supply, and is hence often unpredictable. Some gaseous compounds may derive from thermal breakdown, i.e. pyrolysis, of the chemicals rather than oxidation as illustrated in Tables 3.9 and 3.10. 

Fire Resistant Elastomers. The poly(aryloxyphosphazene) elastomers offer excellent fire resistance without incorporating halogen in the polymer or as an additive. These polymers are self-extinguishing in air and generate only moderate non-corrosive smoke and a minimum of toxic combustion products upon combustion (50-53). The poly(aryloxyphosphazene) elastomers (APN ) have excellent potential for applications such as... 

All precautions relating to compressed gas cylinders must be enforced—the cylinders must be secured to an immovable object, such as a wall they must have approved pressure regulators in place they must be transported on approved carts etc. Tubing and connectors must be free of gas leaks. There must be an independently vented fume hood in place over the flame to take care of toxic combustion products. Volatile flammable organic solvents and their vapors, such as ether and acetone, must not be present in the lab when the flame is lit. 

Conventional fuels such as firewood, coal etc. are not suitable at high altitudes because of difficulty in ignition, low heat output due to lower oxygen content and low ambient temperature. Gel-based fuels were not found very attractive because of their high degree of inflammability and toxic combustion products. 

Recently, work on nitrogen oxidation in the combustion of a fuel mixed with air has become extensive in connection with pollution of the environment by toxic combustion products (including NO). An good review of this research was done by A. N. Heiherst and I. M. Vincent,7 and by A. Macek for coal combustion.8 Detailed experimental and theoretical work on the formation of nitrogen oxides in turbulent gas flames was performed by P. Moreau and R. Borghi.9... 

The purpose of bench-scale reaction-to-fire tests is to measure the flammability characteristics of materials, i.e., ease of ignition, flame spread propensity, heat release, and production of smoke and toxic combustion products. Some tests are designed to measure only one of these characteristics. Other tests are more sophisticated and can be used to measure several characteristics at the same time. 

Oxygenate Toxic Reduces toxic combustion products but contaminates groundwater... 

Aromatics Toxic Form toxic combustion products... 

DIANP is a colorless liquid, which is soluble in acetone, methanol, dimethylformamide, DMSO, ethyl acetate, and benzene. It is not very soluble in water, ethanol, or butanol. DIANP is used in gun propellants and rocket propellants to reduce flame temperatures, toxic combustion products, smoke, and to increase performance without sacrificing bum rate. DIANP is an excellent substitute for nitroglycerine for gun propellants and rocket propellants. ... 

Reduced Smoke and Toxicity. The smoke and toxic products of combustion are a problem of growing concern. Until recently, this problem has been overlooked in developing fire retardants. Future formulations will not only have to limit flame spread, but also limit smoke and toxic combustion products. Addition of smoke suppressants to some formulations may improve some systems. Modification of systems may also be necessary to meet possible code restrictions. More research is necessary in this area to understand the mechanism of smoke production and accumulation. 

Urea-formaldehyde apparently, at least in some formulations, can produce highly toxic combustion products compared to other cellular materials. The University of Utah foimd it only slightly less toxic than phenolic foam, although with nonflaming combustion (830°C) it was found to be the fastest material to incapacitate test animals. Cyanide was found to be the causative agent of death. CO, CO2, and aimnonia are also produced in combustion, all of which are toxic. University of Pittsburgh studies showed UF foam to be only slightly less toxic than PTFE (solid, not foam) (6). 

A 1980 Naval Research Laboratory report provides data on the toxic combustion products evolved by burning polyphosphazene foams, with and without fire retardants. Toxicants produced were CO, CO2, 2-chlorobutane, 1-chlorobutane, benzene, toluene, and trichloroethylene (for foams not coated with fire-retardant paints) (11). 

Since most of the deaths from fires occur in residences, the NFPA proposes the following safety initiatives to improve fire safety (1) increase fire safety education on fire prevention and what to do if a fire occurs (2) install smoke detectors in all homes and check them periodically to ensure they are working properly (3) practice escape plans with the family (4) install residential home sprinklers to prevent fires from spreading once they start (5) develop products for the home that are more fire safe and produce less toxic combustion products (the latter is proposed by the authors) and (6) study the needs of the populations most at risk (the young, the elderly, and the poor) and implement preventive measures. 

To develop a bioanalytical screening test and a mathematical model which would predict whether a material would produce extremely toxic or unusually toxic combustion products. 

Because of the capability of adjusting the mixture ratio to provide non-toxic combustion products, hydrogen meets the fifth criterion. Hydrogen is the only chemical fuel that can meet this criterion. In all respects, hydrogen offers great improvement in environmental safety when compared to any other fuel. 

Pure Natural gas (methane) has little odor so trace quantities of sulfur such compounds, as ethyl mercaptain, are added. These compounds have a powerful odor and serve to warn of a gas leak. They also tend to reduce hydrogen embrittlement of metals. They have been suggested as a solution to the embrittlement problem. Addition of these materials has the shortcoming that these compounds are toxic and can bum to produce toxic combustion products. Unfortunately, the toxicity and polluting combustion products negate the main purpose for the adoption of hydrogen. The use of chemical inhibitors to provide pipeline safety can be avoided by development of other methods. 

Industrial flres are known to cause disasters, affecting both life and property. Literature is rich on this subject If the loss of human life is not caused as a result of convected and radiant heat or direct contact with flames, it may be caused by suffocation due to the inhalation of toxic combustion products or to lack of oxygen. In an explosion workers may by injured by direct impact from debris or by the blast or over-pressure generated by the explosion. Some chemicals are specifically fomulated to explode and are referred to as explosives. Others such as the organic peroxides and some azo and nitro compounds, explode because they are unstable. These may be formed as intomediates in chemical reactions or as the result of a reaction between incompatible chemicals. Table... 

A selective method for determining thiocyanide is based on the quantitative formation of the dithiocyanatodipyridine-copper(ii) complex and its extraction into chloroform. The organic layer is sprayed into an air-acetylene flame and the copper signal at 324.7 nm is measured (detection limit 0.2 mg SCN"1" ). However, the aspiration of chloroform solution into the flame is not recommended since toxic combustion products may be formed. Hence, the organic phase should be evaporated almost to dryness, diluted with ethyl acetate, and the copper atomic signal measured as above (detection limit 0.05 mg SCN 1" ). 

The compatibility of a colorant is assessed not only on the basis of the ease with which it can be mixed with the base resin to form a homogeneous mass but also on the requirement that it neither degrades nor is degraded by the resin. In relation to product functional properties, incompatibihty of a colorant can affect mechanical properties, flame retardancy, weatherability, chemical and ultraviolet resistance, and heat stability of a resin through interaction of the colorant with the resin and its additives. Flame retardancy, for example, may impinge directly on the performance of a colorant. Pressure to produce materials with lower levels of toxic combustion products can involve organic fire retardant additives that interact with the colorant either to negate the effect of the additives or affect the color. 

Heterogeneous catalysts are in a different physical state than the reaction medium, so they are easily separated from the product however, they often work at high temperatures and pressures that are more energy intensive on large industrial scales. An example of a heterogeneous catalyst is a catalytic converter (solid) that catalyzes the transformation of toxic combustion products to less toxic carbon dioxide (CO2), nitrogen (N2), and water (H2O). 

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