Japanese Practical Concepts on Human Error Prevention: 3H, 4M, and 5S
Authors: Nakata Toru 
Published: June 2023

Environment of Quality Control and Safety Management in Japanese IndustriesThe Japanese customers are, in general, very strict on product quality. They can select products from many competitors, so they will not buy products with minor flaws. In addition, high-technology products are required to have very high reliability, so defects on products are critical. Human errors are not allowed in the production. Historically, Japanese economy has been concentrated on mass-manufacturing since 19th century. In the past, the quality control (QC) of Japanese companies was very weak in general. Most of the Japanese think the low quality resulted in unreliability of weapons in the World War II. After the war, most of Japanese companies adopted scientific QC methods from the United States, which is based on statistical analysis to reduce uncertainty in the productions. Japanese companies have developed other methods to manage product quality and workplace safety, which seem very original concepts developed among Japanese industrial society after the war. This paper introduces the Japanese concepts for QC and safety managements, named "3H", "4M" and "5S". Their theoretical backgrounds are also explained. Risks Prediction with 3H-4MIn safety management, it is very important to predict possible incidents beforehand. In Japanese industrial society, many people use the concepts of 3H and 4M for the purpose. “3H” stands for a triple of Japanese adjectives of “Hajimete” (“for the first time”), “Hisashiburi” (“in quite a while”), and “Henkou” (“change”). In most of incidents, the features of 3H are very likely to appear in the story. The Japanese engineers therefore consider 3H features as bad indications that evoke the accidents. “4M” means major four aspects in production processes, namely “Man”, “Machine”, “Material”, and “Management” [1]. (Some engineers may use the variation of “5M” adding “Method” into the four.) In some Japanese companies, supervisors responsible for safety are trained to doubt whether any of 4M is contaminated with baleful features of 3H. For example, supervisors pay special attention on “a new worker”, “a use of a machine in quite a while”, “a change of the instruction rule”, and other 4M with 3H features. This attitude concentrated on risks of “3H in 4M” is a very efficient way to predict large risks hidden in the workplaces, even though it might pay less attention to other minor aspects. Importance of Apparent Order: 5S “5S” is a group of five Japanese words of “Seiri” (organization), “Seiton” (placing things in order), “Seisou” (cleaning), “Seiketsu” (sanitariness), and “Shitsuke” (compliance to rules). Those five features keep simplicity and safety of workplace, that results in suppression of human errors. The 5S features are superficial and easy to see. Supervisors can quickly judge their condition just by observing the workplace. Most of Japanese industries attach top priority to maintenance of 5S to keep quality and safety. Reference 1. Krzysztof Knop, Krzysztof Mielczarek, “Using 5W-1H and 4M Methods to Analyse and Solve the Problem with the Visual Inspection Process – case study”, 12th International Conference Quality Production Improvement (QPI 2018), 2018.