Category: CO Incidents

“Most pilots are aware that carbon monoxide (CO) is a colorless, odorless and tasteless gas contained in exhaust fumes. It is also a common by-product of chemical reactions which can occur upon heating of many petroleum products and silicone-based synthetic lubricants used as aircraft oils and hydraulic fluids.

The carbon monoxide level in blood is measured through a specific blood-gas method and is reported as a percentage. The normal level of carbon monoxide produced by the body’s metabolism is from 0.4-0.7%, but heavy smokers can have much higher levels. Elevated levels of carbon monoxide in the bloodstream can create the effects of hypoxia (oxygen deficiency). Here is one air carrier crew’s experience with CO:

• An electrical/hot plastic smell was noticed in the cabin, and the Flight Attendants reported feeling ill. Maintenance could not find any source of the odor. We started boarding passengers, but boarding was suspended when the odor returned. The Flight Attendants later went to the hospital…they had carbon monoxide levels of [up to] 1.2 [%]. Later that evening, the First Officer and I were tested for carbon monoxide and had levels of 0.5 [%] and 0.6 [%].

  Several hydraulic leaks were discovered in the engine thrust reversers and in the tail cone. The APU was contaminated with hydraulic fluid as well as the air conditioning system.

Headaches and nausea were the symptoms reported by another crew who suspected carbon monoxide exposure.

• After climb we noticed an unusual, faint odor in the cockpit. We tried to determine what the source of the odor might be. In the logbook, we found a previous write-up of an undetermined “ozone” smell in the aircraft. There were also two previous write-ups in reference to unexplained smoke detector activation in the lavatories.

  The First Officer said he was not feeling well. I was also slightly nauseated, had a headache, and was extremely fatigued. Both Flight Attendants also complained of the same symptoms. After arrival, we all agreed we should seek medical attention. It was 3-1/2 hours after the flight arrived that we had blood drawn. The [carbon monoxide levels] ranged from 2.3 [%] to 2.5 [%]. I am aware that these values are above normal. I wonder what the values might have been if the tests were taken just after we landed.

The source of the odors was not identified, but carbon monoxide probably caused the crew’s symptoms. More information about hypoxia and carbon monoxide can be found in the Aeronautical Information Manual–Medical Facts for Pilots, Section 1, Para. 8-1-2 and 8-1-4.

• I remember not being able to find my approach plates, even though they were on the floor beside me. I tried three times to set my destination into the GPS. I was confused as to what to do and panic began to set in. Fortunately, I was able to acquire the airport and complete the approach visually. Upon landing, I discovered that my carbon monoxide detector was jet black! I now suspect my disorientation was a result of carbon monoxide exposure.

Aviation supply shops have no “missing breakfast detector” available at any price. However, small, lightweight carbon monoxide detectors are available…”

https://asrs.arc.nasa.gov/publications/callback/cb_228.htm