What is carbon monoxide?
Carbon monoxide (CO) is a colorless, odorless gas. It can build up indoors and poison people or animals who breathe it.
Where does carbon monoxide come from?
Carbon monoxide is released when carbon-containing fuels like natural gas, wood, or coal are burned with an insufficient supply of oxygen. The greatest sources of CO to outdoor air are cars, trucks, power plants, and other fossil fuel combustion vehicles. Things like unvented kerosene and gas space heaters, leaking chimneys, furnaces, and gas stoves release CO and can affect indoor air quality.
How is carbon monoxide measured?
Chemical concentrations in the air are measured by units of the substance (milligrams, micrograms, nanograms, picograms, or other tiny units of measurement) per volume of air as cubic meters or feet. Carbon monoxide is typically expressed as parts per million (ppm).
Carbon dioxide is measured with a variety of techniques.
Gas filter correlation uses infrared light to shine through air samples and compare how much light was absorbed by the CO in comparison to a control of light shined through a nitrogen gas that does not absorb the light.
The most common household detector uses electrochemical sensors. When carbon monoxide enters the sensor, a chemical reaction occurs that causes the electrical current passing through to surge. The specific amount by which the current increases tells the detector the concentration of carbon monoxide and alerts users if levels become hazardous.
Metal oxide sensors work similarly. As carbon monoxide meets a sensor’s chip, it lowers the metal’s resistance to the flow of electricity. To what degree the metal’s resistance decreases depends on the concentration of the carbon monoxide in the air.
What are the standards for carbon monoxide in the United States?
National Ambient Air Quality Standards (NAAQS) for pollution specify a maximum amount of a pollutant to be present in outdoor air.
Currently, the EPA has 1 hour and 8 hour standards in place for carbon monoxide.
| Pollutant | Standard Type | Mass per Volume | Terms | Date Established |
| Carbon monoxide | 1 hour | 35 ppm | Maximum, not to be exceeded more than once in a year | 30 April 1971 |
| Carbon monoxide | 8 hour | 9 ppm | Maximum, not to be exceeded more than once in a year | 30 April 1971 |
How does carbon monoxide affect people?
Breathing carbon monoxide can cause people to lose consciousness, and potentially die. It’s harmful because it binds to the hemoglobin in the blood, reducing the blood’s ability to carry oxygen. This interferes with oxygen being delivered to the organs. Common effects of CO exposure include fatigue, headaches, confusion, and dizziness from inadequate oxygen delivery to the brain. For people with heart issues, short term CO exposure can reduce the body’s already compromised ability to respond to increased oxygen demands of exercise, stress, or other exertion. Inadequate oxygen in the heart leads to chest pain and decreased exercise tolerance.
During the cold season, carbon monoxide poisoning cases increase. They’re usually related to elevated indoor CO levels from use of space heaters and gas ranges used for home heating with poor ventilation. Over 400 people die in the United States from CO poisoning annually.
Who is most at risk for adverse health effects from carbon monoxide?
Infants, elderly people, and people with anemia or a history of heart or respiratory diseases are most likely to experience health issues from exposure. The unborn babies of pregnant people who are exposed to carbon monoxide in high doses can suffer birth defects.
Because CO is odorless, it often claims the lives of people who are sleeping or drunk because they are unable to recognize symptoms of early carbon monoxide poisoning.
These early symptoms include trouble breathing, tightness in the chest, dizziness, headache, nausea or vomiting, disorientation, and a fast heartbeat. If you suspect you might be in an environment with carbon monoxide gas, go outside immediately and call 911.
How does carbon monoxide affect the environment?
Carbon monoxide has an indirect effect on climate change. It participates in chemical reactions in the atmosphere that produce ozone, which is classified as a climate change gas. Carbon monoxide has a weak direct effect on the climate, but the long-term is under research. CO is classified as a short-lived, climate-forcing agent, prompting CO emission reductions to be considered as a possible strategy to mitigate the effects of global warming.