Carbon Monoxide Aviation Disasters Kill Too Many

Carbon monoxide aviation disasters are under diagnosed and often have deadly results, as confined spaces and high altitude increase lethality of carbon monoxide leaks.

By Rebecca Martin

In 2019, Argentine footballer, Emiliano Sala, had traveled back to Nantes in France to wish farewell to his former teammates after signing a record contract with Cardiff, England on January 19th. Two days after signing his contract, the 28 year old striker and his pilot flew back to Cardiff but never arrived. They lost radar contact near Guernsey. The plane had crashed in the English Channel. After the family commissioned a private search, the body of Emiliano Sala was recovered on February 6th. The body of the pilot was never recovered. The plane was never found. Toxicology tests revealed high levels of carbon monoxide in Sala’s blood. The family actively sought answers in the death of young Sala, hoping to spare other families the pain of such a senseless loss.

carbon monoxide aviation

The FAA warns of the risk of carbon monoxide aviation disasters, as shown by this brochure. Click here to download the PDF. 

Although aviation accidents are usually due to either mechanical failure, weather, pilot error or other human error (air traffic controllers, dispatchers, maintenance engineers) the National Transportation Safety Board (NTSB) has determined that carbon monoxide can be a contributing factor in some instances. The NTSB, through post-crash investigations, has found carbon monoxide aviation disasters is the finding in one to two fatal or serious crashes annually.

NTSD Documented Carbon Monoxide Aviation Disasters

The NTSB has documented 16 U.S. deaths since 1983 due to carbon monoxide aviation disasters. 15 of these involved a pilot impaired by carbon monoxide exposure in the cabin resulting in a crash. The 16th death involved a pilot who succumbed to carbon monoxide while sitting in his idling plane. 5 others were serious injuries incurred during the study period. Analysis of toxicology samples revealed that 360 people had been impacted by carbon monoxide to a significant degree before or after a crash  between 1967 and 1993. Carbon monoxide exposure post-crash is often the result of fire.

It is also certainly true that the number of people impacted by carbon monoxide aviation disasters is higher than reported as a lower exposure might result in symptoms that were simply written off as airsickness or other causes. Because the symptoms dissipate once the flight is over, they are unlikely to be treated or reported. Subsequently a pilot might dismiss mild symptoms over several flights until a larger problem develops.

Cold Weather and Risk of Carbon Monoxide Aviation Problems

The risk of carbon monoxide poisoning while flying is higher in cold weather as many light aircraft are heated by air that has been circulated around exhaust pipes, much like the old Volkswagen Beetles. If there is a defect in the exhaust system, carbon monoxide may enter the cabin when the heat is turned on. But carbon monoxide may enter the cabin in other instances through leaks in the exhaust system. Defects in the exhaust system are the most common cause of carbon monoxide poisonings in airplane crashes. often investigations reveal that planes thus affected have had recent inspections and that these defects were not documented during the inspection.

On March 1, 1996, a Piper crashed shortly after takeoff in Pittsburg, Kansas. Although the plane suffered severe damage, the pilot and passenger reported no injuries. The pilot reported that both she and her passenger had become incapacitated after takeoff. They were taken to the hospital for testing and both tested positive for carbon monoxide poisoning. Records showed that the plane had passed an inspection four hours prior to takeoff. Subsequent examination of the plane revealed several holes in both the muffler shroud and the muffler itself. The NTSB determined that the cause of the crash was an inadequate annual inspection along with the deteriorated condition of the muffler.

Maintenance Key to Avoiding CO Disasters

Piston powered aircraft produce high levels of carbon monoxide and due to design,  have the highest risk for a carbon monoxide related accident. Because the in cabin heating comes from air circulated over the exhaust, any defects in the exhaust system could potentially lead to increased carbon monoxide levels. Because of this, one of the most important safety measures involves an effective maintenance program from qualified and licensed professionals with attention being given to exhaust systems especially in older aircraft.

However, not all defects are going to be discovered in an inspection. In 1998, Dr. Robert Frayser left his hometown airport enroute to Topeka, Kansas. A clear day for flying, he set up his auto pilot and the next thing he remembered was awakening in a hayfield in an almost intact plane. The engine was silent and it took him several minutes to determine that he was in fact on the ground and the only damage was to a wing  which had struck a small tree. He had lost one and a half hours of time. He suffered some minor cuts and bruises and was able to navigate on foot to a farmhouse and was rushed to the hospital where it was discovered that he had nearly fatal levels of carbon monoxide. In this instance the crack in the muffler had opened since the inspection and was not discernible during a pre-flight inspection. If he had remained in the air minutes longer he might not have survived his ordeal and would have succumbed to carbon monoxide poisoning prior to the crash.

Challenges in Identifying Source of CO

The source of carbon monoxide is not identified in every crash. This was true in a 1984 crash in South Carolina which killed a pilot and three passengers. The pilot was overcome and though a teenage passenger tried to follow instructions to land the plane, a fatal crash resulted and the source of the carbon monoxide poisoning was never determined.

It is not only older exhaust systems which can lead to dire consequences. In 1994, a student pilot was treated for severe carbon monoxide poisoning following a crash during an attempted cross-country flight. The muffler had been installed 18 hours earlier after having undergone repairs. A crack in the newly installed muffler was determined to be the source.

Piston powered aircraft are not the only potential source for carbon monoxide poisoning. Turbine powered aircraft have their own problems. There is a risk that carbon monoxide can enter the cabin while sitting on the runway with doors and hatches open or when taxiing behind other aircraft. Although the air can be contaminated by spilled fluids like lubricants and oil seal failures, it is generally believed that the air cleaning mechanisms on Turbine powered aircraft provide for good air quality and that carbon monoxide would only be produced if there were a fire on board.

Commercial Airline Risk of Carbon Monoxide Disasters

The commercial airline industry also understates the risk carbon monoxide disasters as they dismiss the risk of Carbon monoxide poisoning  in turbine powered aircraft.

For example, in 2016, a Delta Air Lines flight from Atlanta to Denver was diverted to Tulsa after 9 people, including a flight attendant, fell ill during the flight. Upon examination, 12 passengers were ultimately discovered to have elevated levels of carbon monoxide in their blood. The airlines was unable to determine the source of the carbon monoxide so it is unknown as to whether the cause was something mechanical or due to the presence of something like an aerosol can in someone’s luggage. The airlines maintained that exposure was minimal though several passengers were nauseous and vomiting during the flight.

Higher Altitude Increases CO Risk

This brings us to the point that carbon monoxide is more toxic at altitude. At higher altitudes there is less oxygen in the air and because carbon monoxide bonds more readily to hemoglobin, the concentrations of carbon monoxide may quickly rise to a troublesome level. This is not only an issue in aviation, it is an issue in all high altitude activities, including mountain climbing. Even though mountain climbers can become acclimated to less oxygen, this only means that the carbon monoxide levels are normally higher and they may respond to treatment less quickly than someone at sea level. This is true of smokers as well who may be at higher risk to lower concentrations. In the case of Robert Frayser, he contends that being a non-smoker may have made the small difference between his surviving or not surviving his carbon monoxide impacted flight and ultimate crash.

However, for the average person, altitude results in a decrease in air pressure resulting in less oxygen. When you add carbon monoxide into that equation, with its affinity to attach to hemoglobin, serious complications can occur.  The carbon monoxide attaches to the hemoglobin producing carboxyhemoglobin which inhibits the oxygen from binding.  Carbon monoxide attaches to the hemoglobin 200 times quicker than oxygen. Even a low level of carbon monoxide over a period of time at high altitude can impair a pilot.

Can’t Smell a Carbon Monoxide Aviation Risk

Many people in aviation still believe that one would have to smell fumes before there would be a risk of carbon monoxide poisoning, but as we have learned, carbon monoxide is an odorless gas not to be confused with the sulfurous smell associated with fuel.

There are symptoms a pilot could become aware of, but very similar to in cases of hypoxia, self-awareness is quickly marginalized by a decrease in cognitive functioning. Initial symptoms of headache and nausea may be forgotten as euphoria sets in or symptoms are dismissed as having other causes until it is too late.

Lack of education is not to blame for these incidents as carbon monoxide awareness is typically covered in all pilot training with an overview of the symptoms and warning signs a pilot might encounter. Counter measures are also covered. According to the Federal Aviation Administration (FAA) pilots suspecting carbon monoxide exposure in the cabin should:

  • Turn the cabin heat fully off.
  • Increase the rate of cabin fresh air ventilation to the maximum.
  • Open windows if the flight profile and aircraft’s operating manual permit such an action.
  • If available (provided it does not represent a safety or fire hazard), consider using supplemental oxygen.
  • Land as promptly as possible.
  • Do not hesitate to let Air Traffic Control know of your concerns and ask for vectors to the nearest airport.
  • Once on the ground, seek medical attention.
  • Before continuing the flight, have the aircraft inspected by a certified mechanic.

Carbon monoxide detectors are essential for safety during flight. But pilots must be careful of the type of carbon monoxide detector they choose. Electronic detectors typically used in homes are not adequate for use in an aircraft. First of all, the air flow and space in a home is far different than the enclosed space in an aircraft cabin. Second, most home detectors are designed to detect 30ppm because requirements were influenced by the costs of eliminating too many emergency responses to lower levels so home detectors only sound when dangerous levels are present. In the cabin of an airplane, these lower levels could be more dangerous. As there is no margin of error with a pilot’s neurological function, any CO could be too much CO.

There are chemical spot detectors which turn black in the presence of carbon monoxide but these have a very limited shelf life and need diligent replacement several times a year.

The only carbon monoxide detectors which should be used in an airplane are those specifically designed for aviation. They detect lower levels of carbon monoxide and feature definite aural and visual alarms designed to catch a pilot’s immediate attention.

Extra care is needed for older aircraft as well as the many home built aircraft out there which may have deviated from original construction plans or used different materials than specified. Attention to the additional stressors caused by weather are also a necessary point to consider as small undetectable fractures may respond to changing temperatures in unexpected ways with a hairline fracture rapidly becoming a crack and thus a hazard.  And, of course, pilots who routinely fly in mountainous areas at higher altitudes must be hyper vigilant due to the greater risks at higher altitudes.

Pilots must be aware of the onset of symptoms such as headache, nausea increasing to drowsiness or dizziness and an increase in respiratory rate. These can quickly turn into more severe symptoms such as confusion, loss of consciousness, seizure and ultimately death. The onset of these symptoms can occur and progress so rapidly that immediate attention is required.

The FAA includes this checklist for preventing the possibility of carbon monoxide exposure during flight:

  • The best protection against carbon monoxide poisoning is to avoid exposure.
  • Aircraft operators and pilots must ensure that heating/ventilation systems and exhaust manifolds in their aircraft are all in good working order, as specified by the manufacturer and the Federal Aviation Administration.
  • Certified mechanics must conduct all required inspections.
  • Special attention should be paid to older aircraft because of corrosion or simple wear and tear.
  • A certified mechanic should verify firewall and aircraft structural integrity and seal any defects.

The NTSB issued safety alerts in 2017 urging maintenance personnel to:

“thoroughly inspect exhaust systems, air ducting, firewalls and window and door seals during 100-hour inspections and annual inspections, and to check heater air inlet cockpit vents for soot, which can indicate the presence of CO.”

Airplanes are not the only aircraft which can produce carbon monoxide. Air medical transport personnel re at risk for carbon monoxide exposure while working under the turning rotors of a medical transport helicopter. Levels of up to 76 ppm have been measured in certain areas under various conditions. Medical personnel should be aware of the symptoms of exposure while working beneath the rotors of a helicopter in operation.

This exposure is also a risk for rescue crews who are often working in an open cargo door situation. Studies have revealed that even though toxic levels were not reached, one third of rescuers had elevated levels of carbon monoxide post-flight.

The NTSB urges all pilots:

“During flight, if you believe you have been exposed to CO, don’t hesitate to act.”







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