Breathe in. Then breathe out. This wonderful process of ventilation keeps us alive: an inhalation of oxygen helps our cells generate energy, while an exhalation of carbon dioxide removes their waste products. Carbon dioxide, or CO₂, has something of a shaky reputation, since it is not only produced by normal biological activity, but also through the burning of fossil fuels: it is a greenhouse gas and therefore has a role in climate change. While international efforts continue to regulate outdoor CO₂ levels in anti-global warming measures, indoor CO₂ concentrations are also strictly regulated by occupational health and safety laws, with a recommended cap at a steady state of 870 parts-per-million (ppm). Human health is affected at high CO₂ concentrations (over 20,000 ppm), and exceedingly high concentrations (over 250,000 ppm) will kill you.

Researchers at the State University of New York and the Lawrence Berkeley National Laboratory in California wanted to study how increased levels of indoor CO₂, such as those found in buildings where there is a drive to minimise energy consumption by reducing ventilation rates, might affect human decision-making capabilities, since brain function is affected by CO₂ levels in the blood. The team injected ultrapure carbon dioxide into an office-like chamber where participants were completing computer-based tests. They used three different CO₂ concentrations – 600, 1000 or 2500 ppm – all of which fall within normal ranges. Baseline performance scores at 600 ppm were average or above average, but when CO₂ concentrations increased to 1000 or 2500 ppm, significant effects were evident: most decision-making performance variables tested, such as the use of initiative and task orientation, showed a decline, in some cases dipping as far as a real dysfunction. This study highlights the potentially economically-significant need for good ventilation in all indoor spaces, especially those where brain function is vital, such as in classrooms and government buildings.

Read the original research article here.

Satish U, Mendell MJ, Shekhar K, Hotchi T, Sullivan D, Streufert S, & Fisk WB (2012). Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance. Environmental health perspectives PMID: 23008272