Thinking of Swiss Cheese: Reason’s Theory of Active and Latent Failures

The Theory of Active and Latent Failures was proposed by James Reason in his book, Human Error. Reason stated accidents within most complex systems, such as health care, are caused by a breakdown or absence of safety barriers across four levels within a system. These levels can best be described as Unsafe Acts, Preconditions for Unsafe Acts, Supervisory Factors, and Organizational Influences. Reason used the term “active failures” to describe factors at the Unsafe Acts level, whereas “latent failures” was used to describe unsafe conditions higher up in the system.

This is represented as the Swiss Cheese model, and has become very popular in root cause analysis and risk management circles and widely applied beyond the safety world.

Swiss Cheese Model

In the Swiss Cheese model, the holes in the cheese depict the failure or absence of barriers within a system. Such occurrences represent failures that threaten the overall integrity of the system. If such failures never occurred within a system (i.e., if the system were perfect), then there would not be any holes in the cheese. We would have a nice Engelberg cheddar.

Not every hole that exists in a system will lead to an error. Sometimes holes may be inconsequential. Other times, holes in the cheese may be detected and corrected before something bad happens. This process of detecting and correcting errors occurs all the time.

The holes in the cheese are dynamic, not static. They open and close over time due to many factors, allowing the system to function appropriately without catastrophe. This is what human factors engineers call “resilience.” A resilient system is one that can adapt and adjust to changes or disturbances.

Holes in the cheese open and close at different rates. The rate at which holes pop up or disappear is determined by the type of failure the hole represents.

  1. Holes that occur at the Unsafe Acts level, and even some at the Preconditions level, represent active failures. Active failures usually occur during the activity of work and are directly linked to the bad outcome. Active failures change during the process of performing, opening, and closing over time as people make errors, catch their errors, and correct them.
  2. Latent failures occur higher up in the system, above the Unsafe Acts level — the Organizational, Supervisory, and Preconditions levels. These failures are referred to as “latent” because when they occur or open, they often go undetected. They can lie “dormant” or “latent” in the system for an extended period of time before they are recognized. Unlike active failures, latent failures do not close or disappear quickly.

Most events (harms) are associated with multiple active and latent failures. Unlike the typical Swiss Cheese diagram above, which shows an arrow flying through one hole at each level of the system, there can be a variety of failures at each level that interact to produce an event. In other words, there can be several failures at the Organizational, Supervisory, Preconditions, and Unsafe Acts levels that all lead to harm. The number of holes in the cheese associated with events are more frequent at the Unsafe Acts and Preconditions levels, but (usually) become fewer as one progresses upward through the Supervisory and Organizational levels.

Given the frequency and dynamic nature of activities, there are more opportunities for holes to open up at the Unsafe and Preconditions levels on a frequent basis and there are often more holes identified at these levels during root cause investigation and risk assessments.

The way the holes in the cheese interact across levels is important:

  • One-to-many mapping of causal factors is when a hole at a higher level (e.g., Preconditions) may result in several holes at a lower level (e.g. Unsafe acts)
  • Many-to-one mapping of causal factors when multiple holes at the higher level (e.g. preconditions) might interact to produce a single hole at the lower level (e.g. Unsafe Acts)

By understand the Swiss Cheese model, and Reason’s wider work in Active and Latent Failures, we can strengthen our approach to problem-solving.

Plus cheese is cool.

Swiss Cheese on a cheese board with knife

Call a Band-Aid a Band-Aid: Corrections and Problem-Solving

A common mistake made in problem-solving, especially within the deviation process, is not giving enough foresight to band-aids. As I discussed in the post “Treating All Investigations the Same” it is important to be able to determine what problems need deep root-cause analysis and which ones should be more catch and release.

For catch and release you usually correct, document, and close. In these cases the problem is inherently small enough and the experience suggesting a possible course of action – the correction – sound enough, that you can proceed without root cause analysis and a solution. If those problems persist, and experience and intuition-drive solutions prove ineffective, then we might decide to engage in structured problem-solving for a more effective solution and outcome.

In the post “When troubleshooting causes trouble” I discussed that lays out the 4Cs: Concern, Cause, Countermeasure, Check Results. It is during the Countermeasure step that we determine what immediate or temporary countermeasures can be taken to reduce or eliminate the problem? Where we apply correction and immediate action.

It helps to agree on what a correction is, especially as it relates to corrective actions. Folks often get confused here. A Correction addresses the problem, it does not get to addressing the cause.

Fixing a tire, rebooting a computer, doing the dishes. These are all corrections.

As I discussed in “Design Problem Solving into the Process” good process design involves thinking of as many problems that could occur, identifying the ways to notice these problems, and having clear escalation paths. For low-risk issues, that is often just fix, record, move on. I talk a lot more about this in the post “Managing Events Systematically.”

A good problem-solving system is built to help people decide when to apply these band-aids, and when to engage in more structured problem-solving. This reliance on situational awareness is key to build into the organization.

Design Problem Solving into the Process

Good processes and systems have ways designed into them to identify when a problem occurs, and ensure it gets the right rigor of problem-solving. A model like Art Smalley’s can be helpful here.

Each and every process should go through the following steps:

  1. Define those problems that should be escalated and those that should not. Everyone working in a process should have the same definition of what is a problem. Often times we end up with a hierarchy of issues that are solved within the process – Level 1 – and those processes that go to a root cause process (deviation/CAPA) – level 2.
  2. Identify the ways to notice a problem. Make the work as visual as possible so it is easier to detect the problem.
  3. Define the escalation method. There should be one clear way to surface a problem. There are many ways to create a signal, but it should be simple, timely, and very clear.

These three elements make up the request for help.

The next two steps make up the response to that request.

  1. Who is the right person to respond? Supervisor? Area management? Process Owner? Quality?
  2. How does the individual respond, and most importantly when? This should be standardized so the other end of that help chain is not wondering whether, when, and in what form that help is going to arrive.

In order for this to work, it is important to identify clear ownership of the problem. There always must be one person clearly accountable, even if only responsible for bits, so they can push the problem forward.

It is easy for problem-solving to stall. So make sure progress is transparent. Knowing what is being worked on, and what is not, is critical.

Prioritization is key. Not every problem needs solving so have a mechanism to ensure the right problems are being solved in the process.

Problem solving within a process

Boscon 2022

I am pretty excited that Boscon, the local ASQ section’s conference is back on and calling for proposals. So for local folks, a good time to share some best practices and case studies.


BOSCON is an annual quality conference hosted by ASQ Boston. BOSCON is the New England signature event where national and international quality professionals hear speakers discuss different quality topics and network with them. The conference focus for 2022 is Navigating Quality Performance in a post-Pandemic World (Risk management, Impact/risk & mitigation of pandemic on companies, Work-life balance, Resource management, Employee Safety, Virtual/ remote workspace, Customer satisfaction, Supply chain).

Tracks and possible focus

  • Technical Quality tool (CAPA, 5S, SPC, Lean 6 sigma, etc);
  • IT/Software (Cybersecurity, cloud, virtual workspace, etc);
  • Pandemic Supply Chain (Lean reconsidered, Change management);
  • Personnel/People (Work-life balance, resource management).

Not interested in presenting, but want to participate as a volunteer?
Contact Snehal Rane  Snehalrane90@gmail.com BOSCON 2022 Chair

B0SCON 2022 PRESENTATION PROPOSAL FORM

We invite you to submit your proposal(s) for BOSCON 2022 oriented towards one of the track areas above.  Please provide a concise and clear description of your session topic and the values it provides to our attendees. 50 minutes are provided for your presentation and any Q&A.

KEY DATES

  • August 15th => Please complete the form referenced below and submit to both Snehalrane90@gmail.com and dmanalan@alum.mit.edu as soon as possible, and no later than August 15th.
  • September 1st => Applicants will be notified if the submitted proposal was accepted, confirmation requires a signed speaker agreement.
  • September 15th => Sign speaker agreement and submit.
  • October 1st => Submit final set of slides by October 1st.

Fill out the form- Word version at

https://1drv.ms/w/s!Aq7kI8QOQQN5hD-FL4JLDqGKF8yc?e=USkE6y

The Supreme Court’s Decision in Dobbs v. Jackson Women’s Health is a Bleak One for the Life Sciences Industry

I think it is no secret that I inherently view Quality as a progressive endeavor, and do not see eye-to-eye with colleagues who are conservative. How anyone can take our anti-Taylorist endeavor and not get to stands like the importance of human rights and the need to center those whose rights are challenged – like women – is beyond me. How can we stand for autonomy and not fight for the autonomy of all.

The silence of quality organizations is deafening.

What I want to write about now is how the roll-back of Roe in Dobbs should be a real clarion call to the life science industry, which needs to stop funding conservative politicians because those politicians do not have our best interests at heart.

The fight over Mifepristone and Misoprostol has already begun. The religious conservatives will go after it, and this reactionary court will need to gut the FD&C and the rest of the regulatory regime behind drugs in this country to let that happen. This will be really bad. It will cause life science companies to pull research, clinical trials, and manufacturing from this country as we will no longer be the gold standard in the life sciences. We will be a joke.

Take action:

  • Give to abortion funds
  • Check your company’s PAC and see exactly who it is giving to and make noise that funding anti-abortion, anti-science politicians is not acceptable
  • Support your colleagues. If you are male-identifying realize that most of your colleagues just got gut-punched today. Support them.