Fire smoke carbon monoxide

Figures 19.19 through 19.21 present smoke, carbon monoxide, and carbon dioxide yield for all the PA6-based materials, respectively. Pure PA6 generally produces the lowest smoke and carbon monoxide, while PA6/NC and PA6/NC (UBE) yield slightly higher values. This is one of the main advantages of nanocomposites, as they do not result in increasing the production of smoke and toxic gases in comparison with most fire retardants. It is important to note that adding FR (both PA6/NP...

Fire can have a tremendous effect on human life, immediate surroundings, and even on the environment. Fire produces carbon monoxide, carbon dioxide, solid carbon particles, and smoke. Heat and high temperature make a fire highly dangerous for the employees of any industry. Death may occur as the concentration of the oxygen in air decreases in case of fire. Therefore, personnel are advised to escape before the fire expands and the temperature rises beyond 65°C. 

Occurrence. Carbon monoxide is a product of incomplete combustion and is not likely to result where a flame bums in an abundant air supply, yet may result when a flame touches a cooler surface than the ignition temperature of the gas. Gas or coal heaters in the home and gas space heaters in industry have been frequent sources of carbon monoxide poisoning when not provided with effective vents. Gas heaters, though properly adjusted when installed, may become hazardous sources of carbon monoxide if maintained improperly. Automobile exhaust gas is perhaps the most familiar source of carbon monoxide exposure. The manufacture and use of synthesis gas, calcium carbide manufacture, distillation of coal or wood, combustion operations, heat treatment of metals, fire fighting, mining, and cigarette smoking represent additional sources of carbon monoxide exposure (105—107). 

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. 

Reduced air preheat and reduced firing rates lower peak temperatures in the combustion zone, thus reducing thermal NO,. This strategy, however, carries a substantial energy penalty. Emissions of smoke and carbon monoxide need to be controlled, which reduces operational flexibility. 

The personal security of our citizens also benefits directly from science and technology. Our police forces are equipped with light, strong bulletproof vests made of modem synthetic materials, and fire rescue personnel wear protective clothing made from temperature-resistant polymers. The smoke detectors and carbon monoxide detectors in our homes are based on chemical processes that detect dangerous substances. Personal security is enhanced in the broadest sense by water purification and by the chemical testing procedures that assure us of clean water and food. 

It is well known that hydrogen cyanide can be liberated during combustion of nitrogen containing polymers such as wool, silk, polyacrylonitrile, or nylons (1, 2). Several investigators have reported cyanide levels in smoke from a variety of fires (3, 4, 5). The levels reported are much below the lethal levels. Thus the role of cyanide in fire deaths would seem to be quite low. However, as early as 1966 the occurence of cyanide in the blood (above normal values) of fire victims was reported (6). Since then many investigators have reported elevated cyanide levels in fire victims (7-13). However, it has been difficult to arrive at a cyanide blood level which can be considered lethal in humans. In this report the results of cyanide analysis in blood of fire victims are reported as well as the possibility that cyanide may, in some cases, be more important than carbon monoxide as the principal toxicant in fire smoke. 

The fact that the main direct cause of death in fires has always been the toxicity of combustion products was already discussed in the National Fire Protection Association (NFPA) Quarterly in 1933 [34]. Smoke contains mainly two types of toxic gases asphyxiants and irritants, but the individual toxic gas associated with the largest fire hazard is carbon monoxide (CO). 

In ideal combustion 0.45 kgs (1 lb.) of air combines with 1.8 kgs (4 lbs.) of oxygen to produce 1.2 kgs (2.75 lbs.) of carbon dioxide and 1.02 kgs (2.25 lbs.) of water vapor. Carbon monoxide, carbon dioxide, nitrogen and water vapor are the typical exhaust gases of ordinary combustion processes. If other materials are present they will also contribute to the exhaust gases forming other compounds, which in some cases can be highly toxic. Imperfect combustion will occur during accidental fires and explosion incidents. This mainly due to turbulence, lack of adequate oxidizer supplies and other factors that produce free carbon (i.e., smoke) particles, carbon monoxide, etc. 

Smokes from hydrocarbon fires consist of liquid or solid particles of usually less than one micron in size, suspended in the combustion gases, which are primarily nitrogen, carbon monoxide and carbon dioxide, existing at elevated temperatures. At normal temperatures carbon is characterized by a low reactivity. At high combustion temperatures, carbon reacts directly with oxygen to form carbon monoxide (CO) and carbon dioxide (CO2). 

Because many materials release HCN when burned, the combined toxicity of HCN and smoke components—carbon monoxide, carbon dioxide, nitrogen dioxide—have been studied. Combination experiments with fire gases showed... 

As an example, low levels of carbon monoxide (CO), together with ingested alcohol, reduce sensitivity to guaiacol, which has a smokey or burnt odor (Engen, 1986). Smokers take up CO. If they also drink, they could be impaired in their ability to detect smoke from a fire. 

High levels of indoor air pollutants result from the use of either open fires or poorly functioning stoves to bum biomass or coal (Ezzati Kammen, 2001). Women, especially those responsible for cooking, are the ones most heavily exposed. Young children who spend their time close to their mothers also have high exposures (Bruce et al., 2000). Many of the substances in smoke from either biomass or coal burning can be hazardous to humans. The most important are suspended particulate matter, carbon monoxide, nitrous oxide, sulfur oxides (coal), formaldehyde, and PAHs (Bruce et al., 2000 Smith et al., 2000). 

In an attempt to look for alternatives to the use of halogenated fire retardants, which function in the gas phase, an approach has been pursued which controls the polymer flammability by modifying the condensed phase chemistry. Silica gel combined with potassium carbonate have been reported to be an effective fire retardant for a wide variety of common polymers, such as polypropylene, nylon, poly(methylmethacrylate), poly(vinyl alcohol), cellulose, and to a lesser extent, polystyrene and styrene-acrylonitrile.49 The cone calorimeter data shown in Table 8.5 indicate that the PHHR is reduced by up to 68% without significantly increasing the smoke or carbon monoxide levels during the combustion. 

There has been a great recent market demand for halogen-free fire-retardant polymers. Zinc borates are also multifunctional fire retardants in halogen-free polymers. They can promote char formation, reduce the Rate of Heat Release, smoke evolution, carbon monoxide generation, and afterglow combustion. When used in conjunction with metal hydroxides, they can also display synergy in fire test performance. 

The range of toxicity test methods is bound to produce different fire conditions, and hence different toxic product yields. Four test methods (NBS Smoke Chamber, NF X 70-100, Fire Propagation Apparatus [FPA], and SSTF) have been compared, primarily from published data64 66 using the carbon monoxide yields and hydrocarbon yields (not recorded in the NFX tests), which are both fairly good indicators of fire condition, for four materials (LDPE, PS, PVC, and Nylon 6.6), at two fire conditions, well-ventilated and under-ventilated. The CO and hydrocarbon yields are shown in Figures 17.9 and 17.10. 

Related problems must be considered in individual products. Bromine, chlorine, and antimony add to the smoke of a fire, while phosphorus and water do not, and some metal oxides can actually reduce it. Toxicity of combustion gases is a major concern but the main problem is that oxidation of carbon compounds in an enclosed space—indoors— produces carbon monoxide, no matter whether the carbon compounds are wood or plastics. Other problems include the cost of flame-retardants, difficulties in processing, and loss of mechanical or thermal properties. 

The colorless carbon monoxide (CO) is everywhere. Wherever there is combustion there is CO it is the predominant product above 800°C. The concentration of CO might vary from 0.1 ppm in clean atmosphere to 5,000 ppm in the proximity of domestic wood fire chimneys (Fawcett et al, 1992) and is present in significant quantities in cigarette smoke (Hartridge, 1920 Hoffman et al, 2001). The atmospheric lifetime of CO is 1 to 2 months, which allows its intercontinental transport (Akimoto, 2003). 

CO has always been a part of the imiverse. However, atmospheric CO has increased over time. When volcanoes erupted, continents collided, and winds embraced the trees sparking fires millions of years ago, all this contributed to the stock of CO. However, when CO first made a significant presence in the air we breathe, humans lived in the open. A very long time must have passed by before humans inhabited caves or built enclosures for protection from the effects of the weather or the tyranny of predators. In the process, however, humankind invited the unwanted guest -carbon monoxide, the silent killer. So where there is smoke, there is not only fire but also CO in terms of human cost, the latter is more dangerous than the former. Yet it must have taken several thousands of years to tame the fire, and over those years CO has claimed many innocent victims who went to sleep after a hearty meal never to wake up. The knowledge of these mysterious events has been unraveled over time. 

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