Atmosopheric carbon dioxide put into perspective
0.04% - current atmospheric CO2 level
0.1% - level indoors, average house
0.28% - average prehistoric atmospheric level sine the Pre-Cambrian
0.5% - maximum recommended level for enclosed envirinments, such as ISS or submerged nuclear submaines
Data from Burt Rutan, aerospace engineer
From a public service advertisement by "Competitive Enterprise Institute":