Section 84.97 - Test for carbon dioxide in inspired gas; open- and closed-circuit apparatus; maximum allowable limits(a)Open-circuit apparatus.(1) The concentration of carbon dioxide in inspired gas in open-circuit apparatus will be measured at the mouth while the apparatus mounted on a dummy head is operated by a breathing machine. An acceptable method for measuring the concentration of carbon dioxide is described in Bureau of Mines Report of Investigations 6865, A Machine-Test Method for Measuring Carbon Dioxide in the Inspired Air of Self-Contained Breathing Apparatus, 1966. Copies of Report of Investigations 6865 may be inspected or obtained from the NIOSH, National Personal Protective Technology Laboratory, P.O. Box 18070, 626 Cochrans Mill Road, Pittsburgh, PA 15236.(2) The breathing rate will be 14.5 respirations per minute with a minute-volume of 10.5 liters.(3) A sedentary breathing machine cam will be used.(4) The apparatus will be tested at a temperature of 27 ±2 °C. (80 ±5 °F.).(5) A concentration of 5 percent carbon dioxide in air will be exhaled into the facepiece.(b)Closed-circuit apparatus. The concentration of carbon dioxide in inspired gas in closed-circuit apparatus will be measured at the mouth while the parts of the apparatus contributing to dead-air space are mounted on a dummy head and operated by the breathing machine as in paragraphs (a) (1) through (5) of this section.(c) During the testing required by paragraphs (a) and (b) of this section, the concentration of carbon dioxide in inspired gas at the mouth will be continuously recorded, and the maximum average concentration during the inhalation portion of the breathing cycle shall not exceed the following limits: | Where the service time is | Maximum allowable average concentration of carbon dioxide in inspired air percent by volume |
| Not more than 30 minutes | 2.5 |
| 1 hour | 2.0 |
| 2 hours | 1.5 |
| 3 hours | 1.0 |
| 4 hours | 1.0 |
(d) In addition to the test requirements for closed-circuit apparatus set forth in paragraph (b) of this section, gas samples will be taken during the course of the man tests described in Tables 1, 2, 3, and 4 of this subpart. These gas samples will be taken from the closed-circuit apparatus at a point downstream of the carbon dioxide sorbent, and they shall not contain more than 0.5 percent carbon dioxide at any time, except on apparatus for escape only, using a mouthpiece only, the sample shall not contain more than 1.5 percent carbon dioxide at any time.60 FR 30355, June 8, 1995, as amended at 80 FR 3907 , Jan. 26, 2015