20. CHEMICALS
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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