Carbon dioxide (CO2) is a colorless, odorless gas naturally present in air at approximately 400 to 420 parts per million outdoors. Elevated indoor CO2 levels above 1000 ppm indicate insufficient ventilation and correlate with reduced cognitive function, decreased alertness, and decision-making ability. Modern building codes require CO2 monitoring and control systems.
Indoor Levels and Health Effects
Outdoor baseline CO2 measures 400 ppm. Indoor spaces with proper ventilation maintain 400 to 800 ppm. Levels exceeding 1200 ppm reduce productivity and learning performance by 50% or more. Schools, offices, and healthcare facilities use demand-controlled ventilation systems to maintain CO2 below 800 ppm, improving occupant comfort and health outcomes.
Monitoring and Control
CO2 sensors cost $200 to $600 and integrate with building automation systems for real-time monitoring. When CO2 exceeds setpoints, systems increase outdoor air intake automatically. This approach reduces energy waste compared to constant high ventilation rates while maintaining indoor air quality and occupant health standards established by ASHRAE 62.1 and EPA guidelines.