From June 1, 2016, it is obliged to carry out a risk assessment for the chemicals specified by Cabinet Order pursuant to Article 57 (1), and the chemicals subject to notice stipulated in Article 57-2 (1) of the Industrial Safety and Health Act. Even in small and medium-sized workplaces, regardless of the type of industry, if the relevant chemicals are handled, a risk assessment must be carried out regardless of the amount handled or the scale of facilities. The Ministry of Health, Labour and Welfare promotes the use of GHS labels and SDSs through "Action with Labels" activities and has developed and provided tools that enable users to carry out risk assessments of chemicals easily by simply entering information such as the names of the chemicals handled and the temperatures at which they are handled. The National Institute of Occupational Safety and Health, Japan (JNIOSH) also provides step-by-step instructions on how to conduct risk assessments for preventing process disasters, such as fire and explosion, in process plants. It is believed that various workplaces are carrying out risk assessments utilizing these tools and methods.

According to the report of "Survey on Industrial Safety and Health (Actual Condition Survey)" in 2017, 37.0% of business operators answered that they carried out risk assessments with regard to the "matters related to the hazards and toxicity of chemicals used in work," an increase from the figure of the same survey in 2016 (31.3%). One of the reasons for this increase may be that more workplaces recognize the obligation to carry out risk assessments of chemicals. On the other hand, in terms of the scale of workplaces, larger workplaces have a higher implementation rate and smaller ones a lower rate. In particular, small and medium-sized workplaces generally do not have spare capacity to carry out safety and health activities, and this is one of the reasons why they do not conduct risk assessments. In addition, an understanding of the characteristics of chemicals and knowledge of chemical reactions are required to carry out risk assessments on the hazards of chemicals, making it difficult to identify the hazard sources and the scenarios that lead to fires and explosions. Accordingly, even in workplaces that carry out risk assessments, the implementation status and results show that appropriate risk reduction measures are often not taken as a result.

Therefore, more specific information and/or material and support tools should be provided in order to carry out more appropriate risk assessments and thereby establish a safe working environment.

This document provides reference information for carrying out risk assessments (JNIOSH method) on the hazards of chemicals in order to prevent fires and explosions for open space work. In accordance with the procedures for carrying out risk assessments of chemicals specified in the guidelines of the Ministry of Health, Labour and Welfare, this document compiles reference information for each of the five steps. In addition, for the first step, this document introduces a method for investigating scenarios that lead to fire and explosion, focusing on the three elements of combustion, as an easy way to start, and the concept and evaluation procedure of human errors.