Carbon Monoxide

Carbon Monoxide

Carbon monoxide (CO) poisoning is a serious concern in aviation. CO is a colorless, odorless gas produced by the incomplete combustion of fuel in internal combustion engines. Due to its undetectable nature without specialized equipment, it poses a silent but significant threat to pilots and passengers. Understanding the causes, symptoms, and corrective actions associated with CO poisoning is essential for ensuring flight safety.

Causes of Carbon Monoxide Poisoning

CO is primarily introduced into the cabin through exhaust system leaks. Aircraft heating and defrosting systems often draw in air from around the exhaust heat exchange, which can become contaminated if the exhaust system is compromised. 

Physiological Effects of CO Poisoning

Once inhaled, CO attaches to hemoglobin in the blood approximately 200 times more readily than oxygen, forming carboxyhemoglobin (COHb). This prevents oxygen from being transported to body tissues, leading to hypemic hypoxia. Unlike other forms of hypoxia, hypemic hypoxia is caused by the blood's reduced oxygen-carrying capacity.

Symptoms of CO Poisoning

Symptoms may vary depending on the concentration of CO and duration of exposure. Common symptoms include:

• Headache

• Dizziness

• Drowsiness

• Nausea

• Blurred Vision

• Weakness or Loss of Muscle Control

• Unconsciousness

Severe CO poisoning can result in death if not promptly addressed. Since CO poisoning symptoms may resemble fatigue or airsickness, it is crucial to remain aware of the possibility of CO exposure.

Detection and Prevention

CO Detectors

Using CO detectors in the cockpit is a reliable method to identify CO presence. Disposable detectors are inexpensive and change color when exposed to CO, providing a visual warning. Some advanced models feature electronic sensors and audible alarms for immediate alerts.

Preventive Measures

To minimize the risk of CO poisoning:

• Ensure proper maintenance of the aircraft's heating and ventilation systems.

• Avoid flying with unresolved exhaust system issues.

• Use CO detectors in the cockpit and check them regularly.

• Be alert to the smell of exhaust gases, though CO may be present without a noticeable odor.

If CO poisoning is suspected during flight, immediate action is necessary to prevent further exposure and mitigate symptoms. Recommended steps include:

1. Turn Off the Heater: Shut down the cabin heater to stop the source of CO intake.

2. Increase Ventilation: Open fresh air vents and windows if possible to allow outside air into the cabin.

3. Use Supplemental Oxygen: If onboard oxygen is available, donning an oxygen mask will provide clean oxygen and reduce CO effects.

4. Descend and Land: Prioritize a descent to a lower altitude and land as soon as practical to receive medical assistance.

Tobacco smoke is another source of CO exposure. Smoking at sea level can elevate CO levels in the blood, leading to physiological effects similar to those experienced at higher altitudes. Smokers may have baseline COHb levels equivalent to those experienced by non-smokers at approximately 8,000 feet, reducing their tolerance to hypoxia and increasing the risk of incapacitation.

Given the increased risk, pilots are advised to avoid smoking before or during flight operations.

CO poisoning remains a preventable hazard in aviation. By maintaining vigilance, using CO detectors, and taking immediate corrective actions when symptoms arise, pilots can ensure the safety of their flights. Regular maintenance and thorough pre-flight inspections are the best defenses against CO exposure. Understanding the risks associated with CO poisoning will equip pilots with the knowledge needed to respond swiftly and effectively in the air.