Understanding Risk Assessment

When people discuss ‘Risk’ there are a lot of different assumptions made about what that means. For me, the study of risk and risk assessment techniques started in 1995. As a technologist and controls designer, I had to somehow wrap my head around the whole concept in ways I’d never considered. If you’re trying to figure out risk and risk assessment this is a good place to get started!

What is risk?

From a machinery perspective, ISO 12100:2010 defines risk as:

“combination of the probability of occurrence of harm and the severity of that harm”

Risk can have positive or negative outcomes, but when considering safety, we only consider negative risk, or events that result in negative health effects for the people exposed.

The risk relationship is illustrated in ISO 12100:2010 Figure 3:

ISO 12100-2010 Figure 3
ISO 12100-2010 Figure 3


R = Risk

S = Severity of Harm

P = Probability of Occurrence of Harm

The Probability of Occurrence of Harm factor is often further broken down into three sub-factors:

  • Probability of Exposure to the hazard
  • Probability of Occurrence of the Hazardous Event
  • Probability of Limiting or Avoiding the Harm

How is risk measured?

In order to estimate risk a scoring tool is needed. There is no one ‘correct’ scoring tool, and there are flaws in most scales that can result in blind-spots where risks may be over or under-estimated.

At the simplest level are ‘screening’ tools. These tools use very simple scales like ‘High, Medium, Low’, or ‘A, B, C’. These tools are often used when doing a shop-floor inspection and are intended to provide a quick method of capturing observations and giving a gut-feel assessment of the risk involved. These tools should be used as a way to identify risks that need additional, detailed assessment. To get an idea of what a good screening tool can look like, have a look at the SOBANE Déparis system.

Every scoring tool requires a scale for each risk parameter included in the tool. For instance, consider the CSA tool described in CSA Z434:

CSA Z434-03 Table 1As you can see, each parameter (Severity, Exposure and Avoidance) has a scale, with two possible selections for each parameter.

When considering selection of a scoring tool, it’s important to take some time to really examine the scales for each factor. The scale shown above has a glaring hole in one scale. See if you can spot it and I’ll tell you what I think a bit later in this post.

There are more than 350 different scales and methodologies available for assessing risk. You can find a good review of some of them in Bruce Main’s textbook “Risk Assessment: Basics and Benchmarks” available from DSE online.

A similar, although different, tool is found in Annex 1 of ISO 13849-1. Note that this tool is provided in an Informative Annex. This means that it is not part of the body of the standard and is NOT mandatory. In fact, this tool was provided as an example of how a user could link the output of a risk assessment tool to the Performance Levels described in the normative text (the mandatory part) of the standard.

Consider creating your own scales. There is nothing wrong with determining what characteristics (parameters) you want to include in your risk assessment, and then assigning each parameter a numeric scale that you think is suitable; 1-10, 0-5, etc. Some scales may be inverted to others, for example: If the Severity scale runs from 0-10, the Avoidability scale might run from 10-0 (Unavoidable to Entirely Avoidable).

Once the scales in your tool have been defined, document the definitions as part of your assessment.

Who should conduct risk assessments?

Lake YogaIn many organizations, I find that risk assessment has been delegated to one person. This is a major mistake for a number of reasons. Risk assessment is not a solo activity for a ‘guru’ in a lonely office somewhere!

Risk assessment is not a lot of fun to do, and since risk assessments can get to be quite involved, it represents a significant amount of work to put on one person. Also, leaving it to one person means that the assessment will necessarily be biased to what that person knows, and may miss significant hazards because the assessor doesn’t know enough about that hazard to spot it and assess it properly.

Risk assessment requires multiple viewpoints from participants with varied expertise. This includes users, designers, engineers, lawyers and those who may have specialized knowledge of a particular hazard, like a Laser Safety Officer or a Radiation Safety Officer. The varied expertise of the people involved will allow the committee to balance the opinion of each hazard, and develop a more reasoned assessment of the risk.

I recommend that risk assessment committees never be less than three members. Five is frequently a good number. Once you get beyond five, it becomes increasingly difficult to obtain consensus on each hazard. Also, consider the cost. As each committee member is added to the team, the cost of the assessment can escalate exponentially.

Training in risk assessment is crucial to success. Ensure that the individuals involved are trained, and that at least one has some previous experience in the practice so that they may guide the committee as needed.

When should a risk assessment be conducted?

Risk Assessment Lifetime Flow Chart
Risk Assessment in the Lifetime of a Product

Risk assessment should begin at the beginning of a project, whether it’s the design of a product, the development of a process or service, or the design of a new building. Understanding risk is critical to the design process. Cost for changes made at the beginning of a project are minimal compared to those that will be incurred to correct problems that might have been foreseen at the start. Risk assessment should start at the concept stage and be included at each subsequent stage in the development process. The accompanying graphic illustrates this idea.

Essentially, risk assessment is never finished until the product, process or service ceases to exist.

What tools are available?

As mentioned earlier in this post, the book ‘Risk Assessment: Basics and Benchmarks” provides an overview of roughly 350 different scoring tools. You can search the Internet and turn up quite a few as well. The key thing with all of these systems is that you will need to develop any software based tools yourself. Depending on your comfort with software, this might be a spreadsheet format, a word processing document a database, or some other format that works for your application.

There are a number of risk assessment software tools available as well, including ISI’s CIRSMA™ and DSE’s DesignSafe. As with the scoring tools, you need to be careful when evaluating tools. Some have significant blind spots that may trip you up if you are not aware of their limitations.

Remember too that the output from the software can only be as good as the input data. The old saw “Garbage In, Garbage Out” holds true with risk assessment.

Where can you get training?

There are a few places to get training. Compliance InSight Consulting provides training to corporate clients and will be launching a series of web-based training services in 2011 that will allow individual learners to get training too.

The IEEE PSES operates a Risk Assessment Technical Committee that is open to the public as well. See the RATC web site.

The Answer to the Scale Question

The Exposure Scale in the CSA tool has a gap between E1 and E2. Looking at the definitions for each choice, notice that E1 is less than once per day or shift, while E2 is more than once per hour. Exposures that occur once per hour or less, but more than once per day cannot be scored effectively using this scale.

Also, notice the Severity scale: S1 encompasses injuries requiring not more than basic first aid. One common question I get is “Does that include CPR*?”. This question comes up because most basic first aid courses taught in Canada include CPR as part of the course. There is no clear answer for this in the standard. The S2 factor extends from injuries requiring more than basic first aid, like a broken finger for instance, all the way to a fatality. Does it make sense to group this broad range of injuries together? This definition doesn’t quite match with the Province of Ontario’s definition of a Critical Injury found in Regulation 834 either.

All of this points to the need to carefully assess the scales that you choose before you start the process. Choosing the wrong tool can skew your results in ways that you may not be very happy about.

*Cardio-Pulmonary Resuscitation

CSA Z1002 Risk Assessment Standard – 60 Day Public Review

Get more information on CSA Z1002. The draft of this document is now available for public review through CSA.

60 Day Public Review Starts Today

CSA (the Canadian Standards Association) has been working on a new risk assessment standard called Z1002 – Occupational Health and Safety Hazard Identification and Elimination and Risk Assessment and Control, since the fall of 2007.

This risk assessment standard is the first of its kind globally and will place the CSA Z100x series of Occupational Health and Safety Management standards at the forefront globally when it is published this year.

This standard is destined to become a Canadian National Standard and will have influence on all the standards in the CSA Catalog that include risk assessment (CSA Z432, CSA Z434, CSA Z460, CSA Z462, etc.)

As of today, the standard is available for public review. This means that you can download a draft copy of the standard for free and have a look at the content of the document. It’s also hoped that you will provide comments on the document that will go back to the technical committee at the end of the Public Review phase on 17-Apr-11 17-Mar-11. Every comment will be reviewed by the Technical Committee. You have the chance to make change in the document before it is published later this year.

Public Review is only open for 60 days, so act quickly! On 17-Apr-11 17-Mar-11 review will close permanently for this edition of the document!

Get The Draft

If you are interested in reviewing and commenting on the draft, please visit:


You can download the draft and you can link to the comments page for the document to provide your thoughts on it.

More Information

Need more information on this standard? Please contact the CSA Project Manager:
Elizabeth Rankin,
ph: (416) 747-2011