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
by Paul Matthews, August 13, 2017 in CimateScepticism
In many ways, the climate debate has hardly changed since I got interested in it about ten years ago. Public opinion wobbles up and down with hardly any real change. The same tired arguments and claims come round again: every climate conference is the last chance to save the planet; the Arctic ice is always about to vanish in one or two years, or ten years; climate scientists continue to be accused of selecting data sets to create hockeysticks and manipulating data; and teams of climate scientists keep producing reports saying almost exactly the same thing as the previous reports, which then get misrepresented and hyped by the media.