Fires, accidental

The term accidental fire refers to all fires other than those which have been deliberately or maliciously started. There are a wide range of causes of fires within the workplace. These will to a certain extent reflect the use to which the workplace Is put. It Is also useful to consider causes of fires In vehicles as In many organisations a workplace may be a vehicle, such as In the case of a long distance lorry driver working for a haulage company. 

Using the current statistics available it can be seen that that the common causes of major accidental fires in the workplace fall under the broad headings of  

Outside deliberate fire setting, fires that are caused by electrical appliances and installations are the most common cause of fires in both industry and the home. There are a variety of different ways that electricity flowing through equipment and installations can cause a fire, these include  

Overloaded wiring - where the electric current flowing in the wires exceeds the rating of the cables. The wiring 

Electrical arcing (or sparking) - this generally occurs where wiring insulation has been damaged by an external occurrence perhaps due to poor location (e.g. under floor coverings). This deterioration to the insulation allows the copper conductors inside the cable to touch one another briefly, or to just make contact with the metal case of an appliance. 

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The calculated detonation velocity in room temperature acetylene at 810 kPa is 2053 m/s (61). Measured values are about 1000-2070 m/s, independent of initial pressure but generally increasing with increasing diameter (46,60—64). In a time estimated to be about 6 s (65), an accidental fire-initiated decomposition flame in acetylene at ca 200 kPa in an extensive piping system traveled successively through 1830 m of 76—203-mm pipe, 8850 m of 203-mm pipe, and 760 m of 152-mm pipe. 

Chun, M. K. et. al., 1989, User s Manual for FTRIN - A Computer Code to Estimate Accidental Fire and Radioactive Airborne Releases in Nuclear Fuel Cycle Facilities, NUREG/CR 30 (PNL-4S 32). PNL, February. 

Half-lives span a very wide range (Table 17.5). Consider strontium-90, for which the half-life is 28 a. This nuclide is present in nuclear fallout, the fine dust that settles from clouds of airborne particles after the explosion of a nuclear bomb, and may also be present in the accidental release of radioactive materials into the air. Because it is chemically very similar to calcium, strontium may accompany that element through the environment and become incorporated into bones once there, it continues to emit radiation for many years. About 10 half-lives (for strontium-90, 280 a) must pass before the activity of a sample has fallen to 1/1000 of its initial value. Iodine-131, which was released in the accidental fire at the Chernobyl nuclear power plant, has a half-life of only 8.05 d, but it accumulates in the thyroid gland. Several cases of thyroid cancer have been linked to iodine-131 exposure from the accident. Plutonium-239 has a half-life of 24 ka (24000 years). Consequently, very long term storage facilities are required for plutonium waste, and land contaminated with plutonium cannot be inhabited again for thousands of years without expensive remediation efforts. 

The influence of metal species like copper has been investigated on the product pattern and yield of PBDD/F (Fig. 7) (ref. 11). This study is relevant to accidental fires of polymeric materials of electronic devices which are associated with various metals like copper. As a result of the presence of the metal species substantial amounts of both PBDF and PBDD are formed. 

The father of this system was the so-called fault tree that was developed for the U.S. missile program. The developers ran into the problem of testing the electric circuits of the Minute Man missiles. No one wants a nuclear warhead accidentally fired into space. Yet all the electric circuits had to be tested so that in case of an attack the missiles could be relied on. The fault tree was a method of predicting the probability of an unplanned launch as a result of testing. If the probability were high then either another way would have to be found to test the circuits or more safety devices would have to be installed. 

It is possible, therefore, that early humans may have accidentally made this type of dish when making fire to warm themselves or for cooking. Could such accidentally fired objects have given prehistoric humans the idea of modeling clay by hand and then firing it into pottery Any such hypothesis... 

Incendiaries are cheap and little training is needed for their preparation and use. Used in very carefully executed operations, the act of sabotage may be concealed in the ashes of an accidental fire. 

The highest possible heat flux from the sun is not possible of igniting common solids. However, magnification of the sun s rays through a fish bowl was found to have ignited thin draperies in an accidental fire. 

Since accidental fire spread mostly occurs under natural convection conditions within buildings and enclosures, some examples of configurations leading to opposed or wind-aided types of spread are illustrated in Figure 8.3. Flame spread calculations are difficult... 

Other accidents could have introduced early cultures to the hallucinatory effects. While harvesting the plant for seeds (for oil) or fiber, accidental fires could have produced a resinous smoke, which was then inhaled. The smoke would have also appealed to the magicoreligious practices of native shamans (30). The smoke itself is inherently evocative of visions and mystery—a natural medium for shamanism It contained a property that could induce a form of trance it was readily consumed by the cleansing power of fire its smoke rose to the abode of the gods and it allowed dreams to be materialized. 

Hazardous substances present in the process are identified on the basis of their flammability, explosiveness and toxicity. The flammability of gases and vapours of flammable liquids is a great concern in the process industries. The result of an ignition can be a fire or an explosion or both. Accidental fires and explosions of flammable mixtures with air often follow the escape of combustible materials or inlet of air into process equipment. 

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. 

All possible precautions must be taken to exclude the chance of accidental fire or explosion by prohibiting smoking and carrying of matches or any other means of producing light in the magazines. 

Zelinski V, Eorenz W, Bahadir M. 1993. Brominated flame retardants and resulting PBDD in accidental fire residues from private residences. Chemosphere 27(8) 1519-1528. 

Cyanide has many sources natural (plant-Cassava), industrial (cyanide salts and nitriles), and accidental (fires). The target organ is the brain death is from respiratory arrest. Cyanide blocks cytochrome a-a3 (cytochrome oxidase) in mitochondria. The toxic level is 1 mg mL-1 in blood. Treatment involves giving dicobalt edetate (chelation). Alternatively, by giving NaNCb, levels of methemoglobin are increased, and this binds cyanide. Detoxication is catalyzed by the enzyme rhodanese, and this pathway may be increased by giving NaS207. 

TATB is an explosive which is resistant to high temperatures, and therefore used in high-temperature environments or where safety from accidental fires is important. TATB is extremely insensitive to initiation by shock and requires a large amount of booster to initiate it. TATB is therefore regarded as an insensitive explosive and will most likely replace HMX and RDX in future explosive compositions. However, the cost of TATB is five to ten times greater than the cost of HMX. 

Safety devices, to prevent accidental firing or firing before the breech is closed, are normally found on the breech mechanism. These devices consist of levers or latches which function automatically. Detailed description of breech mecha-... 

The processing of satellite imagery has shown that fires are not accidental. Fire probability increases, for instance, with fires in the neighborhood of the point considered. Combined analysis of the characteristics of the spatiotemporal variability of fires has made it possible to substantiate 12 typical regimes for fires as well as the dependence of special features of fires on those of the vegetation cover. Though there... 

The 2003 annual dioxin/furan release to the atmosphere was 2.61 g TEQ. The relative contribution of different source categories to total air emission is shown in Fig. 7.2c. The top four contributing classes of local emission sources were (a) coal fired power boilers plants (45.3%) (b) crematoria (13.4%) (c) aluminium production (secondary) (10.3%) and (d) accidental fires—houses, factories and vehicles (9.6%). These... 

Dioxins (PCDDs) occur as contaminants in many agricultural pesticides and can occur in the environment as a result of pesticide usage, although many other industrial sources and natural sources have been identified. The National Dioxins Program (2004) has revealed that major sources of dioxins in the environment are uncontrolled combustion sources such as bush fires and accidental fires which contribute 70% of the total to the air and 80% to the soil whereas waste disposal and land filling contribute 75% of the total to water. 

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