From: "Stuart, Ralph" <Ralph.Stuart**At_Symbol_Here**KEENE.EDU>
Subject: Re: [DCHAS-L] Is Swiss cheese helpful for understanding accident causation?
Date: Sun, 2 May 2021 19:41:39 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: D30845B1-92E6-4723-8C55-05C5A0AAF4F4**At_Symbol_Here**
In-Reply-To <6C525C1C-0689-4C5D-93C7-E634BCACEBF4**At_Symbol_Here**>

>On the flip side, the Swiss cheese metaphor is very helpful for understanding risk management

I agree that the Swiss cheese metaphor is useful for talking about layered protection strategies, primarily for educational purposes. For example, I use it talking about Covid risk management strategies (1. testing/vaccines, 2. distancing, 3. mask/ventilation) and how they interact.

However, the Swiss Cheese, like all other accident models I have seen, are based on linear reasoning which requires more information than is generally available about a process that is subject to failure. I believe that both risk assessment processes and accident causation models are limited by applying a procedural approach to a complex system. (The reason we know that it is a complex outcome is that the accident is not predictable, or people will, and do, take steps to avert the accident.) Changing the boundaries of the system being considered often results in very different results of the assessment / investigation. The CSB report on academic laboratory safety is a classic example of this.

Within that context, I believe that these is a lot of safety value added when people discuss a procedure with a view to safety; particularly if the group invovled is diverse and represents both direct participants in the process and support staff they rely on in case of an unexpected event. However, I donČ??t know of any specific discussion format that produces objective or repeatable results when the results of these discussions by similarly qualified people are compared.

Let me know if you have any questions about this.

- Ralph

Ralph Stuart, CIH, CCHO
Environmental Safety Manager
Keene State College
603 358-2859


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