Are babies in carry cots at risk from CO 2 accumulation?

On 26 October 1971 Dr David Haler, a pathologist, is reported as having said in evidence on a case of cot death in a carry cot "There is no ventilation in a carry cot, so carbon dioxide which is heavier than air sinks to the base of the cot where the child is sleeping" (Oldham Evening Chronicle, 27 October 1971). To clear up a possible misconception implicit in this opinion, it must be pointed out that if individual gases in a mixture settled out according to their densities the atmosphere would be stratified into a very thin layer of carbon dioxide at ground level, then a layer of pure oxygen up to a few thousand feet, with the upper air composed of nitrogen. But, on the other hand, a given mixture of gases will rise or fall when introduced into the atmosphere depending on whether the density is greater or less than that of the surrounding air. Ultimately, of course, diffusion will complete the mixing of these gases with the surrounding atmosphere. The possibility remains that this diffusion is slow enough to allow the carbon dioxide, nitrogen, and oxygen mixture that a baby expires to pool in the base of a carry cot. We investigated the possibility of such an occurrence, and although we concluded that there is no such possibility we think it necessary to report the results, not only to enable medical practitioners to reassure mothers but also to record how alarming some of the preliminary experiments were. We wish to spare any future investigators these alarms