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Ventilatory Response to Carbon Dioxide during Moderate Exercise: Masayoshi TAKAHASHI, et al. National Institute for Resources and Environment—Elevated carbon dioxide (CO 2 ) concentration is one of the most important physiological stressors with closed-circuit breathing-apparatus (CCBA). We determined the ventilatory response to CO 2 during moderate exercise by measuring the . relationship between V E and P ET CO 2 . Based on our findings, it is recommended that the permissible inhaled CO 2 limit for CCBA in the Japan Industrial Standard (JIS) be lowered from 3% to 2%, and that the members of a rescue or fire fighter team who use CCBA be selected on the basis of their ventilatory sensitivity to CO 2 . (J Occup Health 2000; 42: 79-83)

Effects of breathing resistance while inhaling 3% carbon dioxide during steady-state exercise: Masayoshi TAKAHASHI, et al. National Institute for Resources and Environment—The purpose of the study was to determine the effects of breathing resistance on the human body while inhaling 3% carbon dioxide and to evaluate the appropriateness of self-contained self-rescuer (SCBA) criteria in the Japan Industrial Standard (JIS). Eight male subjects volunteered for the study and breathed both normal air and 3% carbon dioxide with both low and high breathing resistance during moderate steady-state exercise. The high breathing resistance produced a pressure level that was almost the same as the upper permitted limit for SCBA in the JIS. Increasing the breathing resistance did not cause any significant effect on the human body while breathing normal air but, in the case of 3% carbon dioxide, the high resistance increased end-tidal carbon dioxide significantly and caused strong distress in the test subjects. Based on these results, it is recommended that carbon dioxide levels be kept low to improve human performance while wearing SCBAs. (J Occup Health 1998; 40: 213-217)