Carbon Monoxide Poisoning: Health Effects (AEN-166)

ISU Extension Publication #: AEN-166
Author: Dr. Thomas Greiner, Dept. of Agricultural and Biosystems Engineering
Iowa State University
Date: 7/96

What is carbon monoxide?

Carbon monoxide (CO) is a colorless, odorless, tasteless, deadly gas. You can’t see, smell or taste it. Carbon monoxide is slightly lighter than air and quickly spreads throughout an entire house.

What produces carbon monoxide?

Carbon monoxide gas is produced when fossil fuel burns incompletely because of insufficient oxygen. During incomplete combustion, the carbon and hydrogen combine to form carbon dioxide, water, heat, and deadly carbon monoxide. In properly installed and maintained appliances gas burns clean and produces only small amounts of carbon monoxide. Anything which disrupts the burning process or results in a shortage of oxygen can increase carbon monoxide production. Wood, coal, and charcoal fires always produce carbon monoxide, as do gasoline engines.

What are the symptoms of carbon monoxide poisoning?

Carbon monoxide symptoms mimic the flu: headaches, fatigue, nausea, dizziness, confusion, and irritability. Continued exposure can lead to vomiting, loss of consciousness, brain damage, heart irregularity, breathing difficulties, muscle weakness, abortions and even death. Because the symptoms mimic so many illnesses, it is often misdiagnosed.

Why is carbon monoxide so dangerous?

When CO is inhaled, it bonds with hemoglobin, displacing oxygen and forming carboxyhemoglobin (COHb) resulting in a lack of oxygen to the body cells. The attraction of CO and hemoglobin is approximately 250 times greater than the attraction between oxygen and hemoglobin. The brain and heart require large amounts of oxygen and quickly suffer from any oxygen shortage. This makes even small amounts of carbon monoxide dangerous. Physical, non-reversible damage can occur.

How much is dangerous?

High concentrations of carbon monoxide kill in less than five minutes. At low concentrations it will require a longer period of time to affect the body. Exceeding the EPA concentration of 9 ppm for more than 8 hours is suspected to produce adverse health affects in persons at risk. The U.S. Occupational Health and Safety limit for healthy workers is 50 ppm. Carbon monoxide detectors, which are designed to protect against high concentration of carbon monoxide are required to sound an alarm when concentrations are greater than 100 ppm. Continued exposure to carbon monoxide can cause permanent brain, nerve, or heart damage. Some people require years to recover while others might never fully recover.

What factors determine the danger level?

The time of exposure, the concentration of CO, the activity level of the person breathing the CO, and the person’s age, sex, and general health all affect the danger level. For instance, a concentration of 400 ppm will cause headaches in 1 to 2 hours. In 3 to 5 hours the same concentration can lead to unconsciousness and death. Physical exertion, with an accompanying increase in respiration rate, shortens the time to critical levels by 2 or 3 fold.

Since 50 ppm is the Occupation Health and Safety limit, is it safe for all people?

No. Respiratory capacity decreases and the risk of heart attack increases at levels well below 50 ppm. The EPA level of 9 ppm appears to be a reasonable limit in homes.

When should CO poisoning be suspected?

Some clues for a family include:

  • Entire family is sick at the same time.
  • Flu-like symptoms decrease while away from the house.
  • Illness is present when gas appliances are in use.
  • Excess moisture on the interior of windows.

What should be done for someone who suffers from CO poisoning?

They should immediately be moved into fresh air and medical authorities consulted. Treatment depends on the amount of carbon monoxide in the bloodstream and assessment of the patient. Often oxygen is administered. In severe cases, patients are treated in a hyperbaric chamber. This is a pressurized oxygen chamber. The combination of oxygen and elevated pressure quickly and thoroughly forces carbon monoxide from the body. Following are the locations of hyperbaric chambers in Iowa.

  • Iowa Methodist Medical Center, Des Moines, Phone: (515) 241-5093
  • Mercy Hospital Medical Center, Des Moines, Phone: (515) 247-3290
  • University of Iowa Hospitals & Clinics, Iowa City, Phone: (319) 356-7706
  • Clarkson Hospital, Omaha, Nebraska, Phone: (402) 552-2000
  • US Air Force 55th Medical Group, Omaha, Nebraska, Phone (402) 294-4400

Won’t the carbon monoxide leave the body naturally?

The half-life of carboxyhemoglobin in fresh air is approximately 4 hours. To completely flush the carbon monoxide from the body requires several hours, valuable time when additional damage can occur. Medical treatment, using oxygen or hyperbaric chambers, can reduce CO damage, speed recovery, and reduce medical problems.

After CO exposure how long do the effects last?

When people lose consciousness due to carbon monoxide poisoning, they will typically have relapses for several weeks. They will suffer from headache, fatigue, loss of memory, difficulty in thinking clearly, irrational behavior, and irritability. Recover can be slow and frustrating. Some individuals suffer permanent brain and organ damage. Victims may be highly sensitive to CO for the rest of their lives.

Can I be tested for carbon monoxide?

Yes. If you have recently been exposed, a breath test can determine carbon monoxide levels. Medical laboratories can measure carboxyhemoglobin levels in the blood. Carboxyhemoglogin levels in the blood drop after the victim is removed from the carbon monoxide source. For this reason, carboxyhemoglobin tests should not be used as the only indicator of the danger of exposure or the possible adverse health effects. Neurological assessment tests, which ask the patient to perform a variety of physical and mental skills, can be used to determine the effects of CO exposure. Because the effects of carbon monoxide may last for months, lack of elevated carboxyhemoglobin levels in the blood does not insure that carbon monoxide is not the cause of health problems. Consult hyperbaric chamber medical staff who are experienced in carbon monoxide poisoning diagnosis for interpretation of results.

What should I do to protect myself from the dangers of carbon monoxide poisoning?

First, purchase a carbon monoxide detector(s). Second, have all heating appliances checked every year by a qualified heating contractor. And third, replace heating units with direct-vent sealed combustion units.

For more information request other notes in the Carbon Monoxide series. Agricultural Engineering Notes (AEN’s) are informally published information releases on topics of current concern to Iowans.