20. CHEMICALS 96 20. Chemicals There is a wide range of different types of chemicals that occur in industrial sectors. Properties and hazards of chemicals, as well as protection against chemical risk factors vary. Chemicals may be harmful to health or the environment, or may cause fire and explosion risk. Dangerousness of a chemical is based on its properties as well as on the amount and the way the chemical is used. The risks associated with the use of chemicals and effects from chemical exposure are often delayed, they can occur after long term exposure. Therefore knowledge of the chemicals to be used and protection against harmful effects is particularly important. Each employee must go through the Material Safety Data Sheet of the chemical being used with his / her supervisor and ensure appropriate protection, proper handling and first aid measures. Properties of gases typically used in shipyards: Acetylene In its pure state acetylene is colourless, odourless and highly flammable gas. Acetylene has garlic-like odour due to trace impurities (sulphur, hydrogen, arsine, phosphine). Acetylene is slightly lighter than air and will rise. Acetylene is a strong reducing agent and reacts violently with oxidants causing fire and explosion hazard. Oxygen Oxygen is a colourless, odourless, and slightly heavier than air gas. For safety reasons, generally industrial oxygen is odorized (dimethyl sulphide). Oxygen is not flammable but it supports combustion and increases the intensity of fire. Gaseous oxygen reacts violently with many chemicals causing fire and explosion hazard. Oxygen leak causes fire risk especially in closed and confined spaces. Clothes and materials saturated with oxygen ignite easily. Liquefied gas Liquefied gases are gaseous mixtures of hydrocarbons, which are stored and transported in liquid form in gas cylinders and containers. Liquefied gases are highly flammable. Liquefied gas is heavier than air, so in case of possible leak, it settles down at floor or ground and therefore accumulates, e.g. in the vicinity of the wells, foxholes and tanks. When a leaking substance is fluid, liquid gas droplets and air condensing water vapour make the gas cloud partially visible. Flammable range may extend beyond the visible fog cloud. When a leaking substance is gaseous, gas cloud is invisible.
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