Figure 4.

The induction of loss of consciousness during 20% per minute filling with CO₂. Time line for loss of consciousness in rats exposed to CO₂ at 20% chamber volume per minute. Animals lose consciousness after approximately 156 s. Bars below the x-axis indicate periods where the animals would be conscious or unconscious. Shaded area shows the likely time/concentration where CO₂ could cause pain (which occurs after loss consciousness in this case). Levels above 5% may cause anxiety and include a significant duration where the animal would still be conscious.