If you search using “carbon dioxide” it will pull out the relevant threads (plus others you don’t want). I got the same number of results but a slightly different set of threads between a normal search and using the “advanced search”.
The principle of CO[SUB]2[/SUB] death is simple. The increased concentration of CO2 entering the lungs stops the blood (haemoglobin molecules to be specific) from releasing carbon dioxide it is carrying. It is therefore unable to pick up any oxygen - even though there is still oxygen present in the gas mix inhaled.
The body continues to use up whatever oxygen it contained and as the level drops it shuts down the conscious part of the brain first – as happens when you faint. Any remaining oxygen is quickly depleted, brain cells then begin to die and death ensues as a result. It happens quickly as a result of the high metabolic rate of warm blooded animals (endotherms).
Pure CO[SUB]2[/SUB] is heavier than air. So when delivered into the top a sealed, air-filled container, with the only outlet also at the top, the CO[SUB]2[/SUB] sinks to the bottom, displacing the air. It is not critical to have 100% CO[SUB]2[/SUB] inhaled. In humans, about 8% or above is fatal, so if you worked on about 20% or above it would give you swift and effective results with feeder animals.
I have never tried this but it should work to enable you to determine the level of CO[SUB]2[/SUB] as it enters the container. Soak several lengths of blue litmus paper in water and then attach them as a strip down the inside wall of the container. As CO[SUB]2[/SUB] reaches the wet litmus paper, a quantity of it should dissolve in the water. This forms a weak acid solution that should be enough to turn blue litmus a pinkish colour.
Blue