You obviously have no idea what you are talking about.
Current atmospheric CO2 level is 400ppm which already has a measurable impact on performance on tasks (compared to 250ppm couple decades ago).
Increasing it to just 1000ppm further degrades performance. And 2500ppm makes it difficult to concentrate on anything complex.
Even slight increase in concentration could lead to drastic changes over time when you consider everybody gets a little dumber.
https://skepticalscience.com/how-sapiens-in-the-world-of-hig...
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EDIT: kragen, I am being throttled so here is my response to your below comment:
When there is plenty arguments and scientific consensus to the contrary, and the person presents numbers obviously derived from thin air, I think it is fair to state the person does not know what they are talking about.
Toxicology is a complex topic. But it is safe to say CO2 becomes toxic way before it becomes lethal. Which is to say you see adverse effects even before the concentration reaches lethal level. It may maybe take hundreds of times before it becomes immediately lethal but it is already toxic at about current concentration or 2-5 times current concentration, depending on who you ask, and not "hundreds of times" higher.