I was having some symptoms that I couldn't identify a cause of, and after a friend mentioned it, I got an indoor CO2 monitor (to accompany my CO monitor), and what it shows is interesting albeit inconclusive.<p>On a daily basis, it shows lows of maybe 400 ppm, which is similar to outdoors. Usually it shows highs of maybe 1000 ppm overnight, which I think is from exhalation, unless it's my furnace. But sometimes it gets up to 1500-2000 ppm, which seems kind of high, and makes me wonder what the cause is or if there are any health effects.<p>For a while, I thought that the high levels were causing headaches and mental impairment, but the correlation seems to have broken down, so maybe it was just a coincidence.<p>Anyway, I think that realistically, direct health effects of CO2 are not going to be the most relevant aspect of climate change, since people generally do tolerate living indoors.