tl;dr: CO2 levels in closed meeting rooms routinely climb past 1,000-2,000 ppm within an hour, and research from Lawrence Berkeley and Harvard shows measurable declines in decision-making and strategic thinking at those concentrations. The impairment is invisible from inside—people just feel foggy and blame the meeting length. Before blaming teams for poor performance or disengagement, check the air: a cheap CO2 monitor and an open window may fix what looks like a people problem.