Carbon Monoxide (Carbon Monoxide)

What is Carbon Monoxide?

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is highly toxic to humans and animals. Because it cannot be detected by human senses, it is sometimes called the "silent killer." CO is produced whenever carbon-based fuels are burned incompletely.

When inhaled, carbon monoxide enters the bloodstream and binds to hemoglobin (the oxygen-carrying molecule in red blood cells) with an affinity 200-250 times greater than oxygen. This forms carboxyhemoglobin (COHb), reducing the blood's ability to transport oxygen to vital organs.

While CO is primarily known as an indoor hazard (from furnaces, vehicles in garages, etc.), it is also an outdoor air pollutant regulated by the EPA. Outdoor CO levels are typically highest near roadways and during cold weather when vehicle emissions are greater and atmospheric mixing is reduced.

Major Sources of Carbon Monoxide

The primary sources of carbon monoxide in outdoor air include:

• Vehicle exhaust - The largest source of outdoor CO, especially in urban areas with heavy traffic
• Residential heating - Furnaces, boilers, and water heaters burning natural gas, oil, or propane
• Wood-burning stoves and fireplaces - Incomplete combustion produces significant CO
• Generators and engines - Portable generators, lawn mowers, and other small engines
• Industrial processes - Steel production, petroleum refining, and chemical manufacturing
• Wildfires and prescribed burns - Major seasonal source of outdoor CO
• Cigarette smoke - A significant indoor source for smokers and those exposed to secondhand smoke

Health Effects of Carbon Monoxide Exposure

According to EPA research, exposure to carbon monoxide can cause a range of health effects depending on concentration and duration of exposure.

Short-Term Health Effects

• Headache - often the first symptom at low exposure levels
• Dizziness and lightheadedness
• Nausea, vomiting, and stomach upset
• Fatigue and weakness
• Confusion and impaired judgment
• Blurred vision
• Shortness of breath, especially during exertion
• At high levels: loss of consciousness, brain damage, and death

Long-Term Health Effects

• Cardiovascular effects - increased risk of heart disease
• Neurological damage from repeated low-level exposure
• Memory problems and cognitive impairment
• Increased risk of stroke
• Adverse effects on developing fetuses during pregnancy
• Worsening of existing heart conditions
• Potential links to depression and other mood disorders

AQI Breakpoints for Carbon Monoxide

The Air Quality Index (AQI) translates Carbon Monoxide concentrations into a standardized scale from 0 to 500:

Who is Most at Risk?

Certain groups are more vulnerable to the health effects of carbon monoxide exposure:

• People with heart disease - CO reduces oxygen delivery, straining the heart
• Pregnant women - CO crosses the placenta and affects fetal development
• Infants and young children who breathe faster and have higher metabolic rates
• Older adults, especially those with cardiovascular or respiratory conditions
• People with anemia - already have reduced oxygen-carrying capacity
• People with respiratory diseases like COPD that impair oxygen exchange
• Workers exposed to CO sources: mechanics, toll booth operators, firefighters

How to Protect Yourself

When Carbon Monoxide levels are elevated, take these precautions to reduce your exposure:

• Install CO detectors on every level of your home and near sleeping areas
• Have fuel-burning appliances inspected annually by qualified technicians
• Never run vehicles, generators, or grills in enclosed spaces like garages
• Ensure proper ventilation when using fuel-burning equipment indoors
• Avoid prolonged exposure near heavy traffic areas, especially in cold weather
• Do not use gas ovens or stovetops for heating your home
• Keep vehicle tailpipes clear of snow or debris during winter
• If CO detector sounds or you experience symptoms, evacuate immediately and call 911

Check Local Air Quality

Monitor current Carbon Monoxide levels in your area using our real-time air quality data. Knowing current conditions helps you make informed decisions about outdoor activities and protect your health.