ASPHYXIANT AND TOXIC GASES

Products of Combustion Heat, hght, smoke, and asphyxiating and toxic gases are produced by fire. In a hot, well-ventilated fire, combustion is usually nearly complete. Nearly all the carbon is converted to carbon dioxide, all the hydrogen to steam, and oxides of various other elements such as sulfur and nitrogen are produced. 

The sections dealing with hazardous materials have been reorganized for consistency with Ref. [2], Two groups of hazardous material are identified asphyxiant and toxic gases, and corrosive and radioactive gases and liquids. 

Asphyxiant and toxic gases may on release affect the nuclear power plant both externally and internally, damaging or impairing safety related systems and... 

Section 7 discusses means of protection for personnel against asphyxiant and toxic gases. This guidance should be followed as appropriate in considering control room habitability issues and other related concerns. 

Release of compressed toxic, anesthetic, explosive, asphyxiating, and corrosive gases locally or beyond the boundaries of a facility Release of radioactive materials... 

Hydrofluoric acid attacks glass, concrete, and many metals (especially cast iron). It also attacks carbonaceous natural materials such as woody materials, animal products such as leather, and other natural materials used in the laboratory such as rubber. Reactions with carbonates, and sulfites and cyanide will produce asphyxiants or toxic gases. Lead, platinum, wax, polyethylene, polypropylene, polymethylpentane, and Teflon will resist the corrosive action of the acid. In contact with metals with which it will react, hydrogen gas is liberated and hence the danger exists of a spark or flame resulting in an explosion in areas where this may occur. 

Hot gases rise by thermal lift. Hence in the open air they will disperse. Within buildings this is a serious cause of fire escalation and toxic/asphyxiation hazards if smoke and hot gases are able to spread without restriction (or venting) to upper levels. A balanced flue can serve to effectively isolate a combustion process in a gas-fired appliance, but must be sound in construction and unrestricted to avoid leaks. 

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). 

Products of Combustion. Heat, light, smoke, and asphyxiating toxic gases are produced by fire. In a hot, well-ventilated fire, combustion usually is nearly complete. 

A few hydrocarbon derivatives from the alkyl-halide family are 2.2 nonflammable compressed gases. This illustrates the wide range of hazards of the alkyl halides as a group. Some are flammable, some are toxic, and some are nonflammable and nontoxic. They can still act as asphyxiants and displace the oxygen in the air. It is important to remember that the primary hazard of the alkyl halides is toxicity. Some of them are also flammable therefore, all must be assumed to be toxic and flammable until the individual chemical is researched and the actual hazards are determined. It is interesting to note that while the DOT lists tetrafluoromethane as a nonflammable, nonpoisonous gas, the Condensed Chemical Dictionary lists the compound as toxic by inhalation. The NIOSH Pocket Guide to Chemical Hazards does not list the compound. The best source of information about this compound and others may be the MSDS (material safety data sheet). Examples of nonflammable Class 2.2 alkyl halides are tetrafluoromethane and trifluoromethane. 

Compressed gases can expose the worker to both mechanical and chemical hazards, depending on the gas. Hazards can result from the flammability, reactivity, or toxicity of the gas, fi-om the possibility of asphyxiation, and from the gas compression itself, which could lead to a rupture of the tank or valve. 

Most deaths from fires do not result from bums. Bums cause only about one-fourth of fire-related deaths. Nearly two-thirds of all fire-related deaths result from inhalation of carbon monoxide, smoke, toxic gases, and asphyxiation. About one-tenth of the deaths are from mechanical injuries, such as injuries from falls or falling material. 

The utihzation of gases during World War 1 (WWl) was a movement toward total warfare. The way that this was characterized was extremely symbolic, but in the end less important (accounting for only about 4 % of deaths). The first attack was in January 31, 1915, by the Germans on the Eastern Front, but the cold weather prevented the action of the gas which did not affect the Russians (and did not stop the completion of the attack). Moreover, the La Haye Convention of 1899 and 1907 interdicted the utilization of asphyxiant or toxic products in projectiles. These gases were used in containers placed in the front lines of combat to take advantage of the winds blowing over the enany lines. 

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