Funding Information No funding information provided.

doi: 10.14814/phy2.12237 The purpose of this study was to verify the previously reported shorter half-time of elimination (t) of carbon monoxide (CO) in females com-pared to males. Seventeen healthy subjects (nine men) completed three ses-sions each, on separate days. For each session, subjects were exposed to CO to raise the carboxyhemoglobin percentage (COHb) to ~10%; then breathed in random order, either (a) 100 % O2 at poikilocapnia (no CO2 added), or (b) hyperoxia while maintaining normocapnia using sequential gas delivery, or (c) voluntary hyperpnea at~4x the resting minute ventilation. We mea-sured minute ventilation, hemoglobin concentration [Hb] and COHb at 5 min intervals. The half-time of reduction of COHb (t) was calculated from serial blood samples. The total hemoglobin mass (HbTOT) was calcu-lated from [Hb] and estimated blood volume from a nomogram based on gender, height, and weight. The t in the females was consistently shorte