Carbon Monoxide (CO)
Also known as: CO
What is CO?
Carbon monoxide is a colorless, odorless gas emitted from combustion processes. At very high levels, which are possible indoors or in other enclosed environments, CO can be poisonous or even fatal.
Sources
The majority of CO emissions come from mobile sources, particularly cars, trucks, and other vehicles or machinery that burn fossil fuels. Other sources include residential wood burning, forest fires, and various industrial processes.
Health Effects
CO reduces the amount of oxygen that can be transported in the bloodstream to critical organs. At low concentrations, healthy individuals may experience fatigue and chest pain. At higher concentrations, vision problems, reduced brain function, impaired coordination, dizziness, confusion, and nausea can occur.
Protecting Yourself
The most reliable way to reduce your exposure is to monitor the Air Quality Index before spending extended time outdoors. On days when the AQI for CO is elevated, consider moving strenuous exercise indoors and keeping windows closed if outdoor air is worse than indoor air.
Sensitive groups — including children, older adults, and people with asthma or heart disease — should take extra precautions at lower AQI thresholds than the general public. High-quality air purifiers with HEPA and activated carbon filters can significantly reduce indoor concentrations. You can track current CO levels for any US city using the search on this site, which pulls directly from EPA AirNow monitoring stations.
EPA Standard
Annual average standard set by the EPA to protect public health.
AQI Scale
US Cities Most Affected by CO
Cities with the most days where CO was the primary pollutant driving AQI.