This data is shown as a bar graph in Fig 7 of Climate Change Drivers, Pangburn. The paleo estimates are near the minimum of the range determined by Berner as shown in the graph at Climate and the Carboniferous
| ppmv | |
|---|---|
| 40,000 | Exhaled breath |
| 20,000 | No symptoms in healthy young people below this level |
| 8,000 | OSHA limit for 8 hr exposure |
| 5,000 | OSHA limit for continuous exposure |
| 5,000 | Approximate level 500 million years ago |
| 1,500 | Artificial increase in some greenhouses to enhance plant growth |
| 1,000 | Approximate level 100 million years ago |
| 1,000 | Common target maximum for ventilation design for buildings |
| 405 | Current atmospheric level |
| 275 | Atmospheric level before industrial revolution |
| 190 | Atmospheric level at end of last glaciation |
| 150 | All land plants and animals become extinct below this level. Land plants become extinct because they are unable to reproduce. Land animals then starve. |
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