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IDENTIFYING THE RISKS
Note: The following description
is not intended to be a definitive technical description.
A simple definition of Risk is:
Risk = Probability x Consequences
The Risk is the risk of the worst case
incident happening. This is a very simple definition and serves to illustrate the basis
for ensuring the dangerous goods can be transported safely.
Probability is the liklihood of an event happening.
Consequences is the effect that event has on people, property and the environment.
Probability is a
function of:
- the stability of the
product
Many products and materials will burn but are not classified as dangerous goods. The
reason is that it is very difficult to get these products to start burning. Hence there is
a low probability of the material being dangerous.
- the type and quality
of the container
The probability of an release of dangerous goods is directly affected by the materials
container. The container separates the dangerous goods from the outside environment.
Small containers are inherently stronger than large ones.
- the conditions of
transport
- Clearly, if a package is subject to extremes of
temperature and pressure as an example, these are more likely to have an adverse effect on
the the integrity of the container.
Some factors to consider when
evaluating the Consequences are:
- the chemical and
physical properties of the material.
-
- Explosions are actually very fast chemical
reactions. A lot of energy is released very quickly. The consequences of such a
release can be severe. Gases and liquids are fluids. That means they flow. The result is
that they have the ability to "carry" their potential hazards over a much wider
area, "spreading" their hazards. The consequences are therefore that much
greater.
-
- the amount of material
present
-
- In most cases, the more of a hazardous substance you
have, the greater the consequences of an incident. This is because there is more potential
energy available. Note that in some cases however, more material actually reduces the
probability of an incident occuring. For example, a tank containing a flammable liquid is
safer when almost completely full than when half empty since it is the vapour above the
liquid which is flammable not the liquid itself.
You may want to consider why a full tank has a higher probability of an incident than one
that is not quite full.
- the environment of the
material
-
- Some materials do not themselves cause incident but
have the capability of turning others which are normally considered non-dangerous into
hazardous situations. For example, calcium carbide reacts with water to produce acetylene
gas, which is highly flammable. It is therefore essential that this chemical is kept dry
at all times. Other chemicals, eg sodium nitrite, are oxiders, this means that they
contribute oxygen which can make ordinary chemical reactions go a lot faster with a huge
increase in the amount of energy released.
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