In my training, one of the concepts I continually hammer on with laboratory risk assessments is the need to develop a detailed scenario for each potential hazard. Just saying that the operator can drop the bottle of acid forces all the members of the team to make too many assumptions as to what might happen. These will have different basis and different probabilities and different consequences.

The operator moves a flammable gas cylinder by hand without a protective cap on and ….

1. Completes the move without an issue
2. Fumbles the move but is able to retain control of the cylinder
3. Drop the cylinder but nothing fails
4. Drops the cylinder and it leaks but not bad enough to create a hazard
5. Drops the cylinder and it leaks badly enough to ignite but the flame is localized, and no one is burned and nothing damaged
6. Drops the cylinder and it leaks badly enough to ignite and burns him but not too badly (first aid)
7. Drops the cylinder and it leaks badly enough to ignite and burns him badly enough to be hospitalized
8. Drops the cylinder and it leaks badly enough to ignite and burns him to death
9. Drops the cylinder and it leaks badly enough that it detonates and kills him and 3 people nearby

Each of these cass needs a detailed step by step discription of how the incident will occurr to allow it to be evelauated. Typically, one would look at #9 or perhaps #6 and determine what mitigative measures are required (oe exist) to prevent it happening. This allows someone to ask "stupid" questions that challenge the assumptions (which are normally actually vry good questions).

People don't like to do this as it takes tiem and effort. (Often one has to review several scenarios for each haard). But it allows everyoen to be sure they are evaluatign the same case, allows anyone to chanllenge assumptions, and makes it a lot easier to determien an approximate probability to aid I nthe assessment.

Just my input.

Richard Palluzi
BE(ChE), ME(ChE), PE, CSP,FAIChE

Pilot plant and laboratory consulting, safety, design, reviews, and training
www.linkedin.com/in/richardppalluzillc/
www.pilotplants.us

Richard P Palluzi LLC
72 Summit Drive
Basking Ridge, NJ 07920
rpalluzi**At_Symbol_Here**verizon.net
908-285-3782

-----Original Message-----
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Ralph Stuart
Sent: Wednesday, November 2, 2022 1:14 PM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: [DCHAS-L] Assessing risk assessments

I’ve had a number of conversations with chemists at all levels of experience and expertise over the years about what constitutes a prudent risk assessment for a laboratory process.

This week, the Safety of Work podcast discusses this under the title of:
Ep. 101 When should incidents cause us to question risk assessments?
https://safetyofwork.com/episodes/ep-101-when-should-incidents-cause-us-to-question-risk-assessments
It uses a fairly extreme example (the Fukushima nuclear disaster) to identify the limitations of quantitative risk assessment and identifies common traps in conducting these.

The discussion is 61 minutes long, so it is hard to summarize, but two key points that I was glad they highlighted were:
- “...every assumption you make is an obligation... An assumption is something that immediately goes onto your to do list of things that you need to check and ensure. The moment you write down my assumption is that the largest wave is 10 meters. That's an obligation to go out and find good evidence that, in fact, that is right. And if not, replace it with the correct number and redesign accordingly."

and

- “When should incidents cause us to question our risk assessments? ...we should be questioning risk assessments constantly. Incidents should just be a reminder that this is something we should be doing constantly."

The takeaways:
• Uncertainty is always present in risk assessments
• You can never identify all failure modes
• Three things always missing: anticipating mistakes, anticipating how complex tech is always changing, anticipating all of the little plastic connectors that can break
• Assumptions - be wary, check all the what-if scenarios
• Just because a regulator declares something safe, doesn’t mean it is
• Answering our episode question: You must question risk assessments CONSTANTLY

Happily, this podcast also provides a transcript of the discussion (in a second tab on the top of the page), so it is easy to review the ideas of the podcast within devoting the full hour to listening to it sight unseen.

I recommend listening if you need to work with people new to risk assessments.

- Ralph

Ralph Stuart, CIH, CCHO
ralph**At_Symbol_Here**rstuartcih.org

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