So, i agree, not Venus. Not even as difficult as living under water. But the air would be hostile by default. So special equipment and housing would probably be required for long term survival. We'll all be settlers living on an earth-like planet.
co2 material safety data sheet says 5000 ppm is max allowable for an 8 hour work day. [1]
co2 levels (appear to) have a direct impact on cognition [2], specifically strategy and information usage.
Ecoene had levels around 2000ppm. It'll be interesting to see if we overshoot or undershoot. Sensitive people start noticing effects at around 1k, perhaps as high as 2k for insensitive people. 2-5k "Headaches, sleepiness and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present." [3]
I don't think there have been any studies of long term exposure to 2k+ ppm (with no recovery time). as far as i know, nobody has to deal with that level of exposure for months or years. It's likely not good. But, as you say, not Venus.
Maybe it's already been written but I would like to read a sci-fi novel where humanity realizes that our atmosphere is at risk and begins a race to capture it. The end result being that the planet's atmosphere is completely sucked up in to massive containers of liquid air. These are controlled by a few entities around the world, i.e. those who were most successful at liquefying air when it was free. Liquid air then becomes the main commodity about which all commerce is based. Who you get your air from determines your social status and vulnerability.
co2 material safety data sheet says 5000 ppm is max allowable for an 8 hour work day. [1]
co2 levels (appear to) have a direct impact on cognition [2], specifically strategy and information usage.
Ecoene had levels around 2000ppm. It'll be interesting to see if we overshoot or undershoot. Sensitive people start noticing effects at around 1k, perhaps as high as 2k for insensitive people. 2-5k "Headaches, sleepiness and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present." [3]
I don't think there have been any studies of long term exposure to 2k+ ppm (with no recovery time). as far as i know, nobody has to deal with that level of exposure for months or years. It's likely not good. But, as you say, not Venus.
[1] https://www.airgas.com/msds/001013.pdf
[2] http://ehp.niehs.nih.gov/15-10037/
[3] https://www.kane.co.uk/knowledge-centre/what-are-safe-levels... (not a great source, but plausible)