Hazardous Chemicals and Explosives

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1. C 2. D 3. C 4. A 5. A 6. C 7. A 8. C 9. C 10. D Q11 Products made up of polymeric materials are combustible when exposed to fire. As they burn, they tend to char and emits a considerable amount of heat. They melt and decompose into monomers or a mixture of simpler substances. When dealing with fire involving polymeric materials it should be clear that, molten material drips from the source. It can be hazardous to the fire fighters or the environment health and safety professional especially if it is dripping from the ceiling. Thermal decompositions of polymeric material produce vapour that initially diffuses on the surface of the polymer where it mixes with atmospheric oxygen and eventually ignite. In case the material does not drip but remains at the immediate site of combustion, they thermally decompose and ignites spreading the fire (Meyer, 2010).
When polymeric material burn, they decompose producing a considerable amount of gases and vapour. As the decomposition process continues, the gas might migrate and accumulate elsewhere especially near the ceiling. Here, they mix with atmospheric air then ignite causing the flame to spread further. Through a phenomenon called flashover, decomposition of a polymer can be caused by heat conducted, or radiated from another point. Combustible gases produced by thermal decomposition ignites and spread the fire to other room or sections. At flashover, safe exit from a room is not possible, and the living condition of a room are usually unbearable with the rooms temperatures ranging from 600 – 800-degree centigrade (Meyer, 2010).
In addition, the vapour and gases produced by polymeric fire are dangerous and fatal. They include nitrogenous, sulfurous gases. A high concentration of carbon monoxide is also produced. If in an enclosed area, the level of these gases soar to a dangerous level within few minutes. The fire may affect areas far away the source. The hot gases and vapour produced can spread by convection through ventilation systems and other openings and end up affecting people elsewhere in the building. Polymeric fire produces a considerable amount of soot that when inhaled draws toxic gases into the bronchi and lungs (Meyer, 2010).
Of all the three gases produced, Carbon Monoxide(CO) can be the most dangerous to the Environment, Health and Safety or the Fire Services professional responding to the scene. Once inhaled, the gas combines with the haemoglobin in the blood circulation system and converts into carboxyhemoglobin that causes an ineffective delivery of oxygen to the body tissues. At concentration levels of 667 PPM, CO causes a conversion of over 50% of haemoglobin to carboxyhemoglobin, and this may result into fatal (Meyer, 2010)..
When materials made from polyacrylonitrile smolder and burn, they produce a colourless compound called Hydrogen Cyanide. It is an extremely poisonous compound. Although it has a life-threatening nature, few fatalities have been linked to Hydrogen Cyanide at scenes of fire. Additionally, carbon monoxide and carbon dioxide are produced by the oxidation of Carbon atoms, and Hydrogen atoms oxidize producing water while nitrogen atoms oxidize forming nitric oxide and nitric dioxide.
Trinitrotoluene (TNT) as a military explosive due to some of it characteristics that includes:
• Though highly explosive, TNT is insensitive to heat, shock and friction, and this makes it safer to handle. The compound will only detonate when confined or when huge amounts are intentionally activated.
• The compound does not react with atmospheric moisture and even after being stored for a long time, it does not decompose spontaneously.
• TNT can be melted using steam without explosion. This makes it possible for melted TNT to be safely mixed with other explosives or oxidizers to create the desired weapon (Meyer, 2010).