Fire toxicity asphyxiant gases

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. 

COz is a nonflammable gas, therefore it does not present a tire or explosion hazard. The gas is generally considered toxic but will displace oxygen in the air, since it is 1.5 times heavier that air it wall settle and air supplies will be pushed out of the area. The CO2 gas is considered an asphyxiation hazard to personnel for this reason. Since the gas is odorless and colorless it cannot be easily detected by human observation in normal environments. Fire protection CO2 gas is normally stored under high pressure as a liquid and expands 350 times its liquid volume upon release. 

EXPLOSION and FIRE CONCERNS nonflammable gas NFPA rating (none) can contain variable quantities of the low-sulfur fluorides (e.g., sulfur pentafluoride) which are highly toxic very reactive chemically, and corrosive in nature materials can hydrolyze on contact with water to yield highly toxic and very corrosive hydrogen fluoride may act as a simple asphyxiant when pure and in high concentrations incompatible with disilane may be explosive hazardous decomposition products include monosulfur fluoride, tetrasulflir fluoride, sulfuryl fluoride, sulfurous fluoride, sulfuric fluoride, decasulfur difluoride and other toxic fluoride compounds if cylinders are involved in a fire, keep cool with water spray. 

There is no doubt that without nitrogen (or other inert gas) many more people would be killed by fire or explosion. Nevertheless we have paid a heavy price for the benefits of nitrogen. Many people have been asphyxiated by it. In one group of companies in the period 1960-1978, 13 employees were killed by fire or explosion, 13 by toxic or corrosive chemicals, and 7 by nitrogen. It is our most dangerous gas. 

Carbon dioxide and certain halon compounds have a specialized application for fires in electrical equipment where a non-conducting medium is important. All are toxic to a degree, and operate either by smothering the fire or by a chemical reaction which inhibits combustion. Gas extinguishers must not be used in a confined space because of the toxic risk or the risk of asphyxiation. 

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). 

The toxic properties of chemicals can be found in a reference such as Hazardous Chemicals Desk Reference (Sax and Lewis 1987), which lists a number of chemicals alphabetically by name. For instance, n-butane is classified (by the Department of Transportation) as a flammable gas, is moderately toxic via inhalation, causes drowsiness, is an asphyxiant, poses very dangerous fire hazard when exposed to heat, flame, or oxidizers, and is highly explosive when exposed to flame. Information about safety and environment is also provided and updated by websites maintained by government agencies, such as the U.S. EPA, the National Institute of Occupational Safety and Health, and the National Safety Data Sheet. 

SAFETY PROFILE Mildly toxic by inhalation. Causes drowsiness. An asphyxiant. Very dangerous fire hazard when exposed to heat, flame, or oxidizers. Highly explosive when exposed to flame, or when mixed with [Ni(CO)4 + O2]. To fight fire, stop flow of gas. When heated to decomposition it emits acrid smoke and fumes. 

Properties Colorless gas insol. in water m.w. 100.02 m.p. -142 C b.p. -78.4 C Toxicology LC50 (inh., rat, 4 h) 40,000 ppm mildly toxic by inh. asphyxiant questionable carcinogen tumorigen TSCA listed Precaution Flamm. exposed to heat or flame dangerous fire risk explosive limits 11-60% inhibited monomer will explode if ignited uninhibited form will explode above 2.7 bar ... 

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