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THE TAKEAWAY: Tightly sealed home insulation traps human respiratory emissions, elevating indoor CO2​ to levels that measurably degrade decision-making.

Outdoor air typically contains ~420 ppm of carbon dioxide. In sealed, unventilated bedrooms or offices, human respiration can push levels past 1,200 ppm within hours. Concentrations above 1,000 ppm cause mild lethargy, impaired concentration, and disrupted REM sleep. Simple continuous ventilation or fresh air exchanges restore optimal baseline cognitive function.