Why Do We Disrespect the 4th S of 5S?

By Jon Miller Updated on May 28th, 2020

The 5S method is widely recognized as a fundamental and foundational part of Lean management. Without the basic discipline to remove clutter and distractions, put things back where they belong, and plug our leaks and sources of cutter, we live in chaos. We lose things, we waste time searching or choosing, we cause accidents and spills. When we empower people to apply the 5S method to design their workspace and process, they can identify what they need to work in safe, productive and high-quality ways.

The Most Disrespected of the 5S

When asked “which is the most important of the 5S?” many will answer “self-discipline” or “sustain”? They are not wrong, although the question may be. But rarely do we ask, “which of the 5s is least important?” We answer this question by what we choose to ignore.

The 4th S in the 5S method is seiketsu. The English translation is sanitary, clean, unpolluted. This is the least respected of the 5S words. We change its meaning and as a result, neglect cleanliness.

In terms of activity to make clean and sanitary, there seems to be considerable overlap between the third and fourth S. The third, seiso, translates as “sweep”. It means to make clean. If sweeping is cleaning and the result is cleanliness, why not combine them rather than stating the obvious?

Sort, Straighten, Sweep, Sanitize, Self-discipline

Browse the literature or do a Google search of “what is the 5S method” and one finds abundant and varied explanations of the five words beginning in S. There is general consensus on sorting, straightening or setting in order, sweeping, and self-discipline. But the fourth 4 is commonly misrepresented as standardize, spic and span, schedule, stabilize, or shine. Even some companies we hold in the highest regard for their dedication to continuous improvement boldly declare seiketsu to mean “standardize”.

I have been guilty of this as well over the years. Very few businesses that I consulted with seemed to need a lot of work in workplace sanitization and cleanliness. The 5S method was popular before I arrived on the scene. The prevailing but incorrect translation seemed harmless at the time. After all, the first three S, when done thoroughly, take care of the last two S to a large degree. Why fight a pedantic fight over the definition of the 4th S?

We made a decision when we created our online 5S course to refers to the 4th S as “standardize” rather than “sanitize”. There have been no complaints, nor reports of Lean journeys derailed by unsanitary conditions. No harm done?

Where did Sanitize Come From?

What was the design intent of including seiketsu or “sanitize” as the 4th S? Does it still hold? Should the original meaning be rigorously applied? Or was the change a needed update for modern conditions? The specific origins of the 5S method is not well documented. Those who popularized it were not its creators. We can only speculate how sanitize became the 4th pillar of the 5S.

Factories were much filthier places 70 years ago. Soap and hot running water were not as readily available in post-war Japan. Much of the factory workforce came from the countryside, where people had a higher tolerance for dirt. Medical infrastructure was still being rebuilt. Vaccination regimes were not yet common. Food and medicine were not plentiful. Workers who got sick made others sick. Illness led to absenteeism, which reduced productivity and raised cost. Conditions were such that sanitizing was important.

The CANDO method from the Ford Motor Company predates the 5S method. Many believe it to the model for 5S. Yet is missing a “sanitize” or “cleanliness” element.

Cleaning up
Ongoing improvement

Perhaps this is because during this period, the United States enjoyed a much higher standard of living, health and medical care.

There is additional support for this line of thinking. Where we do find “sanitize” in use as the 4th S, it is often in developing countries where conditions are not ideal, and sanitation remains a priority.

Sanitizing as Prevention at the Source

Cleanliness commands greater importance in some industries. These include food & beverage processing, pharmaceuticals, laboratories, medical products, healthcare and similar fields. In these situations, damage from contamination is not limited to product appearance or function. It can directly affect the health or even life of the customer. However, in these fields the higher requirement for cleanliness is often government-regulated. Sanitizing is already a practice, with or without a 5S method. They practice prevention because the cost of correction is far too high in comparison.

A basic principle of Lean thinking is to find and contain a problem at its source. This prevents its spread. Mask-wearing is common in places like Japan, Hong Kong or Korea not because people fear catching the flu. Their cities are dense. Public transport is ubiquitous. A sense of social responsibility causes individuals to contain their microbes with a mask.

In the West, COVID-19 has revealed a different set of cultural norms. Some of us view the choice to wear a mask is as a sign of fear of catching the virus from others. Likewise, not wearing a mask is as an act of courage, defiance to authority, or defense of personal liberty.

The masks are prevention at the source. Sanitizing is prevention at the source. The source of adherence or non-adherence to these practices is our values.

Restoring Sanitize as the 4th S

Does it even matter? Is it acceptable to make up our own definitions of these terms? Perhaps so, as long as the overall gist of our activity is to “remove the unnecessary, arrange the necessary, keep it clean, and make this routine”. For those of us whose workplaces are much more sanitary than in past centuries, it may seem backwards to adhere to terminology rooted in early 20th century factory conditions. Turning on a black light may change your mind.

It’s true that sweep and sanitize are close in activity and meaning. But there is an important difference. The 3rd S sweeps away macro filth and clutter. The 4th S wipes away, washes or disinfects microbes. Microbes are invisible to the naked eye. The explicit method and practice of sanitizing keeps us aware of these contaminants.

These days we are relearning the basic lesson that sanitizing saves lives. The medical world acknowledged a century and a half ago that handwashing by surgeons prevents death by infection. Many of us are just now picking up the habit of washing our hands with soap and water for twenty seconds. Perhaps it’s time to pay the 4th of the 5S more respect by restoring sanitize to our vocabulary of Lean practices.

  1. James

    May 25, 2020 - 9:18 am

    Timely comments, of course, but it certainly made me want to read on…
    Nicely put.


    May 27, 2020 - 11:22 am

    While the CANDO method from the Ford Motor Company predates the 5S method, it was Hiroyuki Hirano who developed 5S within his overall approach to production systems.
    SEIKETSU (Standardize)
    This aspect of the 5S focuses on Standardization, making the first three S’s (SEIRI, SEITON and SEISO), a constant routine. The emphasis here is on visual management, an important aspect to attain and maintain standardized conditions to enable the individuals always act quickly.
    Taiichi Ohno, considered to be the father of Toyota Production System said “Without Standards there can be no improvement” He also said that “Standards should not be forced down from above but rather set by the production workers themselves”.
    Steps in SEIKETSU are:
    • Identify the way different people are doing an activity
    • Discuss and choose the best way
    • Make this the standard method once everyone accepts it
    • Convert this into a written Standard giving it a reference Code number
    • Ensure that everyone does the same work only as per the Standard
    • After accepting as the Standard, review it from time to time and improve it as necessary
    • Identify the weaknesses in the Standard and upgrade it
    SEISO (Shine) places emphasis on cleaning so that things are clean, in other words, carrying out cleaning as a form of inspection, ie getting rid of waste and foreign material.
    Steps in SEISO are:
    • Identify which parts, areas, zones, etc. are to be cleaned each shift/twice daily, daily, weekly, monthly etc.
    • Plan for systematic daily or periodic cleaning
    • Ensure cleaning material and cleaning tools are available at an accessible place
    • Identify and remove the root causes of such defects/dust/dirt
    Cleaning, Sanitization, Disinfection and Sterilization can all be grouped under SEISO.
    Cleaning removes dust, dirt, grime and some germs. Sanitization reduces the micro organisms to a safe level.
    Disinfection is the highest practical level of decontamination. Kills Microorganisms on inanimate objects that can cause infection.
    Sterilization is the process of making something free from bacteria or other living organisms. Common methods of Sterilization include Physical and Chemical methods.
    Therefore, let us please retain the intent of SEIKETSU, which is to Establish procedures and schedules to ensure the repletion of the first three ‘S’ practices.

    • Jon Miller

      May 29, 2020 - 10:03 am

      Hello Rama

      Thanks for your comment. It somewhat makes my point about the misunderstanding / disrespect of the 4th S. As a professor and researcher, Hirano who wrote about and popularized 5S. He did not invent 5S, nor systematize it. His take on 5S has become mainstream, and is at least in part responsible for changing the meaning of “cleanliness” to “standardize”. Maintaining a neat and orderly condition certainly fits within the broad definition of “cleanliness”. But it leaves out the sanitary aspect of the word and shifts that focus into the third S.

      • Christian Pezo

        May 29, 2020 - 10:18 am


  3. Amit Lunia

    May 30, 2020 - 6:18 am

    Well I would combine both of the above point of views and use the term “Seiketsu” to mean Standardise clean up, Seiketsu will ensure compliance to the new standards of cleanliness , by maintaining cleanliness, and avoid periodic large-scale cleanup projects,
    A good description is given at https://world-class-manufacturing.com/5S/Seiketsu.html
    In fact I would say , My statement is taken from this site

    • Jon Miller

      May 30, 2020 - 10:23 am

      Thanks for your contribution Amit. That’s a good webpage.
      What’s sometimes lost when the 4th S is stated as “standardize” is that it becomes mechanical or procedural. The idea may be to sustain a neat, clean and organized condition. But this must come from internal motivation and awareness of the importance of cleanliness, purity, sanitariness. Otherwise we struggle to make people comply with standards with which they may not agree, or whose purpose they may not understand.

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