Chest compression is a major cause of death at accidents caused by slope failures. This study aims to propose safety requirements in terms of strength for protective equipment to save workers' lives from chest compression as a result of being buried in soil. Several sets of large scale model tests were carried out to simulate slope failures. A model chest was newly developed to directly measure the acting earth pressure during burying. The acting earth pressure to the chest finally decreased to the overburden pressure value while an impact pressure increased sharply at the beginning from hits from falling soil blocks. Therefore, the required strength must be clarified for values of impact pressure by being limited to shallow burying within a depth of 1m. In addition, two sets of critical values of pressure and strain against the chest compressions were investigated in ergonomic studies. A number of safety factors on dynamic loading were calculated, taking into account the safety code on safety harnesses, and then a value of the impact pressure at slope failures was derived. A parallel spring model was introduced to represent a human chest wearing the protective equipment. Finally, this study indicates the safety requirements in terms of strength for the chest protection equipment at shallow burying caused by small slope failures.

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This paper proposes a safety design to prevent labor accidents due to the nullification of safeguards. Causes of nullification are specified in cases of accidents involving industrial machinery. They are categorized in terms of laborsaving. It turns out that the safety requirements to improve mechanical equipment vary according to the categories. An issue of conventional safety design is discussed considering the nullification causes. A new approach to deal with the issue is introduced and a methodology of system control is demonstrated as an example of its application.

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Roll box pallets (RBPs) are four-wheeled cages that are used in many industries and contribute to efficient logistics services. However, we found that many work-related injuries to the hands and feet occur during manual handling of RBPs in the logistics industry. To obtain an overview of RBPs accidents in various industries, the features of RBPs accidents and incidents were investigated based on reports of less than 4 days' absence from work in four prefectures in 2008. Our results showed that 55% of accidents occurred in the transportation industry, and the rest occurred in other industries. With respect to the type of injury, bruising accounted for 55% of accidents. In addition, these accidents were categorized into four types, making up 85% of the total number of accidents. It was considered that fingers, hands, and feet protectors and protective footwear that can protect toes were effective measures against such accidents. Therefore, it is necessary to provide RBPs workers with a manual reflecting the actual work-related injuries and specific countermeasures to avoid such accidents. Moreover, it is important to improve the RBPs design.

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The hand-arm vibration exposure level of workers who occupationally use hand-held power tools was measured in four operating processes of aluminum-die-cast manufacturing. Also the workers orally answered questions regarding the daily exposure time to hand-arm vibration caused by the use of hand-held power tools, subjective symptoms in the hand-arm during / after daily tool operation, and countermeasures used to reduce vibrations on the to the hand-arm system. According to vibration dose evaluation based on the daily equivalent vibration exposure, the exposure limit durations were a little more than 1 hour for polishing operation in the finishing process and less than 1 hour for final polishing in the inspection section. Actually the workers in these sections are engaged in polishing, using the tools for 5 hours in a day. Almost all of the tool operators complained of temporary fatigue and numbness of the hand during / after the daily tool operation. However no use of anti-vibration gloves was observed in these workplaces. The results suggest the current workplaces require the systematic control of hand-arm vibration exposure based on the concept of energy-equivalent daily vibration exposure, which includes educational orientation on the use of anti-vibration gloves.

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Every year, there are about 10 fatal occupational accidents, and about 250 accidents involving at least 4 days of lost work time, that involved mixing and crushing machines. However, the degrees to which accidents are critical, and the degree of risk, have not been determined for different industries, machine types and work types. Therefore an attempt was made to quantify these risks by calculating the total work-days lost for these items using a technique for quantitative risk evaluation based on work-days lost. The analysis results showed that the total number of work-days lost for all mixing and crushing machines was 131.6×103 days/year. Industries with the highest risk were, in order; cleaning/slaughter, chemicals, food product manufacturing, and stone and clay product manufacturing. These 4 industries accounted for about 68% of the total work-days lost. The highest risk by machine type were, in order; crushing machines, stirring/mixing machines, grinding machines, food processing machines, and kneading machines. These accounted for about 80% of the total. By work type, risk was highest for cleaning, followed by, in order: maintenance/inspection/repair, raw material loading, operation/manufacturing, and obstruction removal. These types of work accounted for 75% of the total.

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