This study aimed to examine exposure evaluation procedures that can be used to prevent exposure to chemicalsubstances in university experiments. Measurements were conducted to assess four types of exposure evaluation methods in students performing analytical chemistry experiments. These measurements, A and B measurement, personal sampling method, personal exposure monitoring guideline, and video exposure monitoring, are mainly used in the risk assessment of chemical substances in the workplace. Based on the characteristics of each evaluation objective, appropriate exposure evaluation procedures were examined, considering the characteristics of the student experiments. The results suggest that it is possible to simultaneously assess health hazard risk and the work environment and to perform exposure assessment efficiently and effectively by collecting samples using personal samplers and evaluating the quantitative values according to the Personal Exposure Monitoring Guidelines and the evaluation calculation method of the personal sampling method. In addition, we found that this simultaneous implementation of video exposure monitoring can identify high exposure operations that require improvement and can extract residual risks even where no improvement is required.
Carbon dioxide fire extinguishers are effective against small fires and fires from electrical equipment, however, the danger of carbon dioxide poisoning must be kept in mind especially when the fire extinguishers are used indoors. In this study, we measured concentrations of carbon dioxide and their changes over time with carbon dioxide monitors (measurable range of 0 to 9,999 ppm) when using a carbon dioxide fire extinguisher indoors. The concentration at a height of 50 cm from the floor exceeded 10,000 ppm approximately 20 seconds after discharge of the extinguisher. When the window was open for ventilation, it exceeded 10,000 ppm for about 40 seconds then decreased rapidly. In contrast, when the window was closed, it exceeded 10,000 ppm for more than 200 seconds, and the subsequent decrease in concentration was gradual. For the concentration exceeding 10,000 ppm, the maximum concentrations were estimated using exponential curves. It was estimated to be approximately 20,000 ppm and 40,000 ppm when the window was open and closed, respectively. Concentrations at a height of 150 cm from the floor were up to 4,000 ppm regardless of whether the window was open or closed. In general, headaches and dizziness occur when the carbon dioxide concentration exceeds 30,000 ppm, and unconsciousness occurs when the concentration exceeds 100,000 ppm. Our results suggest that the carbon dioxide concentration near the floor is relatively high and there is a risk of poisoning, but it is not too high to immediately lose consciousness. It should be avoided to directly discharge a carbon dioxide fire extinguisher to the face, but our results indicate that it is considered safe to use it if there is ventilation such as by opening windows and if it is not used in an extremely narrow space.