>"But a new Danish study failed to confirm these findings. The paper, published in February 2016 in the journal Building and Environment, reports no cognitive decline even when subjects breathed air containing 5,000 ppm carbon dioxide."

>"Even scientists who have found an effect say more research is needed before they are convinced that modest amounts of carbon dioxide are a public health problem. Satish says that, so far, nobody even knows by what biological mechanism carbon dioxide might dim the brains of test subjects."

I feel like people are way too readily accepting this CO2 cognitive decline thing. There are other comments here saying that we know CO2 causes cognitive decline.