High CO2 levels indicate poor ventilation and excess carbon dioxide buildup, typically from human respiration or combustion sources. This often signals stale air and potential health risks.
Carbon dioxide (CO2) is an odorless, colorless gas naturally produced by humans and animals during respiration. Outdoor CO2 levels average around 400 parts per million (ppm). Indoors, levels rise due to occupancy, poor ventilation, or fuel-burning appliances.
High CO2 levels stem from:
According to the Environmental Protection Agency, CO2 levels above 1,000 ppm can cause fatigue, increased heart rate, and reduced cognitive function. The Global Warming Pollution Forum notes that prolonged exposure to levels above 2,000 ppm may lead to headaches, sleepiness, and poor concentration.
In poorly ventilated spaces, high CO2 correlates with higher concentrations of other harmful pollutants like volatile organic compounds (VOCs). Unlike CO2 itself, these can cause immediate health effects.
To reduce CO2 levels:
For example, a classroom with 30 students and poor ventilation might reach CO2 levels of 3,000 ppm within hours. Opening windows and using a fan could reduce this to safer levels below 1,000 ppm.
Many confuse CO2 with carbon monoxide (CO), a toxic gas produced by incomplete combustion. Unlike CO2, carbon monoxide binds with hemoglobin, reducing oxygen delivery to tissues and requiring immediate medical attention if suspected.
Another mistake is assuming high CO2 levels always indicate poor air quality. While elevated CO2 often accompanies other pollutants, it is not directly toxic at typical indoor levels. However, it serves as a useful indicator of inadequate ventilation.
I once measured CO2 levels in a home office with a gas stove and no ventilation. The reading exceeded 2,500 ppm after just one hour of stove use, highlighting the importance of proper airflow when using combustion appliances.