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A Systematic Approach to Risk Assessment

Risk assessment is all about probability

Jonathan Klane, M.S.Ed., CIH, CSP, CHMM, CIT

Jonathan Klane, M.S.Ed., CIH, CSP, CHMM, CIT, is senior safety editor for Lab Manager. His EHS and risk career spans more than three decades in various roles as a...

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Risk seems like an easy concept. Asking yourself, "Can I get hurt?" is a good starting point for understanding risk assessment, but it's much more than that. We need structured ways to assess and characterize risk.

What is risk?

Risk is a simple equation using three factors: risk = severity x exposure x probability. Here's a simple question to determine each factor:

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  • Severity: how bad could this be?
  • Exposure: how close am I to the bad thing?
  • Probability: what are my odds of the bad thing harming me?

When distilled into their simplest forms, these factors seem quite straightforward. But far from it—accounting for them can be quite complex and requires careful thought. Some examples can help illustrate what it means to adequately weigh these factors:


One can use the various hazard types and strengths to differentiate severity. For example, some hazard types include flammable, corrosive, infectious, ionizing, etc.

Take the first hazard category of flammability. One can break it down into four primary factors for flammable liquids. These are:

  • Vapor pressure: how much gets into the air?
  • Flash point: how easily will it ignite?
  • Lower explosive or flammability limit (LEL/LFL): how much is needed to explode?
  • Molecular weight: where in the airspace will the vapors travel?

Together, they combine to create a flammability risk profile—the first factor in the risk equation.


Exposure is typically the most straightforward factor to assess. A few questions might be:

  • Am I using the chemical?
  • Am I breathing in infected airborne particles?
  • Am I too close to the radioactive source?

Understanding exposure goes beyond simply identifying proximity to a hazard; it involves a detailed assessment of the duration, frequency, and intensity of contact with the hazard. For instance, a worker's exposure to chemical substances isn't just about being in the same room as the chemicals. It also matters how long they're exposed during a single session, how often these sessions occur, and the concentration of the chemicals in their immediate environment.


Now comes the hard part: probability. The concept of possibility is our brain's default—it's essentially a binary value ("Can this event happen or not?") that we can determine quickly and easily in survival situations. Our ancestors didn't care about the probability of a saber-tooth tiger hiding in the tall grass—they only cared about whether it was there. While thinking in terms of possibility is what comes to us naturally, calculating probabilities can go a long way in reducing risk exposure and avoiding life-or-death decisions. When working in the lab, it's vital to assess the probability of a risk—not just its possibility.

Characterizing and communicating risk

There are many tools and techniques to characterize risk, such as the RAMP framework. A few other examples include:

  • What ifs: "What if there is a spill/fire/power outage/I'm bumped," etc.
  • Pre-mortem: if I die doing this work, what killed me?
  • Storytelling: use lab stories for context, bonding, perceptions, data/details, sharing, etc.

When communicating risk perceptions to others, consider which tool best suits your specific context. Sometimes, storytelling is more effective than pre-mortems, and vice versa. Next, compare your subjectivity with others. How do you each perceive it? Communicating is all about listening first and throughout, then sharing and discussing.

By taking a systematic approach to assessing risk and effectively communicating risk perceptions, your team can arrive at a more holistic and accurate risk perception than anyone can solo.