by K. Richard, August 20, 2018 in NoTricksZone

Over the years there has been a sustained effort to portray human exposure to very high levels of CO2 as toxic.  A new study undercuts these claims, as the decision-making performances of controlled-experiment participants were not impaired when exposed to CO2 concentrations as high as 15,000 ppm. 

by Blair King, April 10, 2016

Specifically the Bureau of Land Management Health Risk Evaluation for Cabon Dioxyde  points out:

A value of 40,000 ppm is considered immediately dangerous to life and health based on the fact that a 30-minute exposure to 50,000 ppm produces intoxication, and concentrations greater than that (7-10%) produce unconsciousness (NIOSH 1996; Tox. Review 2005). Additionally, acute toxicity data show the lethal concentration low (LCLo) for CO2 is 90,000 ppm (9%) over 5 minutes (NIOSH 1996).

See also The Lake Nyos Disaster

See also here