Science experiments can often be
dangerous, from dealing with corrosive chemicals in the chemistry lab to working with some
deadly virus in the biology lab to handling radioactive substances in the physics lab. Hazards can be found everywhere in the
world of science. Therefore, it is vital that every
experimentalist is versed in how to minimize the chances of anything go wrong.
In this video, we will discuss the
meanings of the terms hazard, hazard severity, and risk. Now, in everyday language, we often use
the words hazard and risk interchangeably. However, they actually mean subtly
different things. So let’s have a look at their
According to the Canadian Centre for
Occupational Health and Safety, a hazard is defined as a potential source of damage, harm,
or adverse health effects on something or someone. In other words, a hazard is an object or
an event or anything else that could cause potential damage. We’ve actually already mentioned a few
hazards in this video earlier on.
Corrosive chemicals often found in a
chemistry lab are an example of a hazard, so are microbes or microorganisms that could be
potentially dangerous to human health grown on Agar plates and so are radioactive materials
commonly found in physics labs. So these are all types of hazard. But even things that you don’t expect to
be hazards can be hazards, for example, a set of stairs. Stairs are hazard because you can trip
over them and injure yourself. So even the most mundane things can
potentially be hazards.
Now we’ve thought about what the word
hazard means, so let’s now think about hazards severity. Hazard severity is basically a measure of
how adverse or how bad the effects of a hazard can be. So for example, coming back to our
radioactive substance, there can be very negative effects such as radiation sickness or even
genetic mutation or contamination of the surrounding environment with radioactive
materials. And so, the severity of this hazard is
Now if we compare this to our set of
stairs, then the stairs also have a relatively high hazard severity, especially when going
down the stairs. Because if somebody was to trip over on
these stairs whilst going down, it is possible that they could fall down the entire flight
of stairs and maybe break some bones and in the worst-case scenario actually die. Later on in the video, we’ll see examples
of hazards which have relatively low severity.
But for now, let’s look at another
definition. The word “risk” is used to describe the
likelihood or probability of an adverse or bad outcome due to a given hazard. Now, this depends on a couple of things,
firstly, what the hazard itself is. So for example, if we come back to our
radioactive substance, we’ll see that if we don’t take the proper precautions, then the
likelihood of something going wrong is quite high because a radioactive substance will
release ionizing radiation which will often do damage to a living organism such as via
genetic mutation. And so, handling something like a
radioactive substance can be a fairly high-risk process.
However, risk does not just depend on
what the hazard actually is, it also depends on the exposure to a hazard. For example, if we take the proper
precautions such as by encasing the radioactive substance in very thick lead, then our
exposure to this radioactive substance is reduced. Equivalently, a block of radioactive
material on the other side of the world is not going to do any damage to us because we
aren’t exposed to it. Therefore, the exposure to a hazard is
equally important when assessing the risk of a hazard.
Perhaps, a better example of this is when
we consider corrosive chemicals in a chemistry lab. If we wear gloves and carry the corrosive
chemical in a tightly sealed container, then the risk of something going wrong is much lower
because we’re not exposed to that chemical. Conversely, if we carry in an open
container whilst running around the lab and the container is nearly overflowing and we’re
not wearing gloves, then the risk is much higher.
So these three terms that we’ve just
learnt about are important to think about when designing an experiment. We need to ensure that the experiment is
conducted in a safe manner as possible, safe not just for humans, but for any wildlife
around the humans as well as any property and even the environment surrounding the
experiment. Let’s now take a look at a few examples
of these terms in action.
Which of the points of the graph of risk
and hazard severity best corresponds to the activity of measuring the temperature of water
being boiled in a beaker that is heated over a Bunsen burner?
Okay, so in this question, we’ve been
told that we’ve got a beaker of water. And this beaker is heated with a Bunsen
burner until the water is boiling. Now, we’re trying to measure the
temperature of this water. So we need to stick a thermometer in the
water as well. Now, let’s start by identifying the
hazards in the setup.
Well, first of all, we’ve got boiling
water which could be spilled and that is a hazard. And secondly, we’ve got a Bunsen burner
which is switched on; that’s also a hazard. So these are the two hazards in our
setup. Now of course, there are more. But these two are the main ones.
So let’s now think about the hazard’s
severity. In other words, if things were to go
horribly wrong, how bad would it be? Well, if somebody was to first of all put
their hand close to the Bunsen burner, then they would get potentially burned by it and that
is actually really severe. And as well as this, because we’re
dealing with boiling water, that could potentially be spilled resulting in scalds and yet
more burning. So for the hazard severity, we can say
that due to the possibility of scalding and burning, the severity is high.
And finally, let’s think about the
risk. Now, risk is to do with the estimated
probability of something going wrong: how likely is it that something bad will happen? Well in this situation, if we’ve got a
beaker of water that’s boiling on a Bunsen burner, assuming that everything else has been
set up correctly, such as the tripod on which the beaker is balancing, then the only thing
that the experiment has to do in order to measure the temperature is to put the thermometer
into the beaker of water.
Now they can do this when the water is
boiling which is slightly dangerous or they could have done this before the water was even
boiling, even before the Bunsen burner was switched on. Therefore, it’s likely that the order in
which the scientist set up this experiment is that they fill the beaker with water, put the
thermometer into the beaker, set up the tripod and the beaker on top of it, and only then
switch on the Bunsen burner. Once all of that is done, the only thing
that the scientist has to do is to read the temperature on the thermometer.
This means that they don’t have to touch
the setup whilst the water is boiling. And hence, the likelihood of anything
getting knocked over or them touching the Bunsen burner is really low. They’re basically not exposing themselves
to the hazard: neither the boiling water, nor the Bunsen burner. The only thing they’re doing is looking
at the thermometer from far away. And hence, the risk can be said to be low
because of the low exposure to the hazards.
So let’s now look at this graph that
we’ve been given at the question. On the vertical axis, we’ve got
increasing hazard severity as we go up. And on the horizontal axis, we’ve got
increasing risk as we go across. So for this science experiment, we’ve
said that the severity is high and the risk is low. That means that we’re looking for a point
that is high up on the hazard severity axis, but low down on the risk axis.
We can draw dotted lines across and up
from both of these points on the two axes and see that the point at the intersection of
these two dotted lines is point 𝐴. In other words, point 𝐴 is the one which
shows high hazard severity, but low risk. And so, our answer to this question is
that point 𝐴 corresponds to the activity of measuring the temperature of water being boiled
in a beaker that is heated over a Bunsen burner.
Okay, let’s look at another similar
example: which of the points on the graph of risk and hazard severity best corresponds to
the activity of measuring the weight of a cup of water that is filled to the brim by a
high-speed flow of water?
Okay, so in this question, we’ve got a
cup that is filled to the brim with water by a very high-speed flow of water. We’re trying to measure the weight of the
water which we can do by measuring its mass first and remembering that the weight of an
object is found by multiplying the mass of that object by the acceleration due to gravity on
Earth 𝑔. So we can place this cup on a weighing
In order to answer this question, what we
need to do is to assess the risk and the hazard severity of this entire experimental
setup. So let’s start by considering the hazards
in this experiment. Well, one potential hazard is the water
itself. It could get everything wet for
example. And in this experiment, it seems to be
the main hazard.
So let’s think about the hazard
severity. The hazard severity is how bad the
effects would be if something were to go wrong and in this case if the water went
everywhere, such as for example on the hands of the scientist doing this experiment or on
the mass balance or on the books that the scientists is using to record the results of this
experiment. Then, the water will make everything
However, this is not a particularly
severe situation. All that will happen is a few things get
wet and nothing more. There’s nothing corrosive or dangerous or
explosive or harmful or damaging. And so, we can say that the severity of
the hazard in this experiment is low.
Finally, let’s consider risk. Now, risk is talking about the likelihood
or probability of something going wrong or in other words the probability of the hazard
being allowed to actually be hazardous. Well, in this question, we’ve been told
that a high-speed flow of water is filling the cup and the cup is filled to the brim.
This means that it’s very likely that the
water will overflow because it’s difficult to control the water and ensure that it fills the
cup up to the brim without overflowing especially because it’s a high-speed flow of
water. So the risk is actually quite high in the
situation even though the severity is low. In other words, the probability of
something going wrong is high. But the damage that that thing going
wrong will do is low.
So looking at our graph now, we’ve got a
graph of hazard severity on the vertical axis and risk on the horizontal axis. We want to find the point of the graph
that is high risk, but low severity. So let’s move along the risk axis and go
to a higher risk position and move up the hazard severity axis but only a little bit because
we want a low hazard severity. So we can then draw a dotted line across
from the hazard severity axis and up from the risk axis.
The point that intersects both of these
two lines is point 𝐸. And hence, that is the answer to our
question. The point on the graph that corresponds
to the activity of measuring the weight of a cup of water that is filled to the brim by a
high-speed flow of water is point 𝐸.
Alright now, let’s summarize what we’ve
learnt in this lesson. In this video, we defined a hazard as a
potential source of damage, harm, or adverse health effects on something or someone. As well as this, we saw that hazard
severity is related to help adverse the effects of a hazard can be. Thirdly, we saw that risk is defined as
the likelihood or probability of an adverse outcome due to a given hazard. And finally, we looked at hazard severity
against risk graphs which can be very useful when planning an experiment and insuring that
it’s as safe as possible.