Cautions issued for wearing “respiratory protective equipment” used by workers engaged in restoration operations at the TEPCO Fukushima Daiichi Nuclear Power Plant
The Ministry of Health, Labour and Welfare (MHLW) requested the National Institute of Occupational Safety and Health, Japan, to conduct a survey on the use of a respiratory protective equipment (proper fitness (*2) of the full-face mask (*1)) worn by workers engaged in restoration operations at the TEPCO Fukushima Daiichi Nuclear Power Plant in order to prevent internal exposure. A survey report was issued recently.
The MHLW has provided TEPCO with guidance regarding the implementation of measures based on suggestions made in the report.
[Summary of the report]
- The leak rates (*3) were measured and evaluated regarding the respiratory protective equipment (full-face mask) currently worn by six site foremen and one staff member of the head office engaged in restoration operations at TEPCO Fukushima Daiichi Nuclear Power Plant. Factors causing the leakage were identified, and then the equipment was improved accordingly. The effectiveness of the improvement was confirmed by measuring the leak rate after the improvement.
- The leak rates of the respirator worn by the six site foremen initially ranged from 1.1 to 56.0% (for an average of 17.4%).
- The two main factors that caused the leakage were as follows:
- Eye glasses, cotton caps, or frontal hair that cause a gap between the face and respiratory protective equipment, and
- The shape or size of users’ face did not fit properly with the respiratory protective equipment.
- The following measures improved the leak rates to less than 5%.
- Applying a seal piece to eye glasses to fill the gap between the temples of the user and the respiratory protective equipment,
- Not allowing cotton caps or frontal hair to get caught between the face and respiratory protective equipment, and
- Selecting the respiratory protective equipment that fits the shape and size of users’ face.
- The mask equipped with an electric fan (*4) demonstrated favorable protection effects in terms of leak rates. However, its heavy weight and problematic shape were pointed out.
- Based on the results, the five points suggested to TEPCO were as follows:
- Take extra measures for workers who wear glasses,
- Select appropriate respiratory protective equipment,
- Encourage workers to take measures to prevent leakage when wearing the respiratory protective equipment,
- Consider introducing powered air purifying respirator, and
- Improve the education training program for new workers regarding the respiratory protective equipment.
*1 The full-face mask covers the eyes, nose, and mouth. There is also a half-face mask that only covers the nose and mouth.
*2 Proper fitting refers to the correct degree of contact between the respiratory protective equipment and the face of the person who wears it.
*3 The leak rates refer to the ratio of air in working environment leaked through the gap between the respirator and face into the air used for respiration. More specifically, the concentrations of dust inside and outside the mask are measured to determine the ratio.
*4 The powered air purifying respirator refers to a respiratory protective equipment operated by power to provide filtrated air.