Risk Matrix

A Risk Matrix is a tool used in the Risk Assessment process, it allows the severity of the risk of an event occurring to be determined.

A risk is the total of each of the hazards that contribute to it. The risk of any particular hazard, H, can be defined as its probability, p, multiplied by its consequence, c. In layman's terms: how likely it is to happen and how bad it would be if it happened.

$Hazard\; =\; P\_H\; *\; C\_H$

Therefore the total risk, R, of an event, e, is the sum of the "n" potential hazards that would result in that event:

$R\_e\; =\; sum\_\{i=0\}^\{n\}\; H\_\{i\}$

The Consequences can be defined as:
*Catastrophic - Multiple Deaths
*Critical - One Death or Multiple Severe Injuries
*Marginal - One Severe Injury or Multiple Minor Injuries
*Negligible - One Minor Injury

The Probability is identified as 'Certain', 'Likely', 'Possible', 'Unlikely' and 'Rare'. However it must be considered that very low probabilities may not be very reliable.

An example Risk Matrix would be as follows:

The company or organisation then would calculate what levels of Risk they can take with different events. This would be done by weighing up the risk of an event occurring against the cost to implement safety and the benefit gained from it.

An Example

The risk of being crushed may be made up of the hazard of being crushed by a car hitting you, the hazard of having a piano dropped on you and the hazard of being in the path of a stampede. Each hazard has probability and a consequence. In this example the probability of being hit by a car is much greater than that of being hit by a piano or a stampede. However the consequence of being hit by a car is less than that of finding yourself under a piano.

These are shown in the table below with a few others: