![Cabin pressure and Bleed air control panels on a Boeing 737-800](https://upload.wikimedia.org/wikipedia/commons/f/fb/Cabin_pressure_and_Bleed_air_control_panels_on_a_Boeing_737-800.jpg)
A fume event occurs when
bleed air
Bleed air is compressed air taken from the compressor stage of a gas turbine upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPCs) valves bleed air from high or low stage engine compressor sections. Low ...
used for
cabin pressurization
Cabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for passengers and crew flying at high altitudes. For aircraft, this air is ...
and air conditioning in a pressurized aircraft is contaminated by fluids such as engine oil, hydraulic fluid, anti-icing fluid, and other potentially hazardous chemicals.
How cabin pressurization works
Because
airliner
An airliner is a type of aircraft for transporting passengers and air cargo. Such aircraft are most often operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an ...
s fly at very high altitudes, the cabin must be pressurized to provide a safe quantity of breathable oxygen to passengers and crew.
The cabin is pressurized with
bleed air
Bleed air is compressed air taken from the compressor stage of a gas turbine upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPCs) valves bleed air from high or low stage engine compressor sections. Low ...
tapped from the jet engine's compressor sections, which are prior to the combustion sections. That air is very hot and must be cooled by heat exchangers before it is directed into the air conditioning units, which cool it even further.
The
Boeing 787
The Boeing 787 Dreamliner is an American wide-body jet airliner developed and manufactured by Boeing Commercial Airplanes.
After dropping its unconventional Sonic Cruiser project, Boeing announced the conventional 7E7 on January 29, 2003, ...
pressurizes its air with electrical compressors rather than the engines to prevent fume events.
Handling of fume events
In the event of fumes or smoke in an aircraft, flight deck crew will wear pressurised oxygen masks in order to avoid breathing in irritating fumes. Goggles are also available if necessary. Cabin crew may be able to use portable oxygen masks if they identify the fume event in time. If the fumes do not subside after an attempt is made to diagnose and fix the problem, the flight is diverted to a nearby airport. In a severe fume or smoke event, the aircraft might descend to an altitude of or lower where it can safely be depressurized.
An FAA-funded study found that fume events occur on 1 in 5,000 flights; some planes may have multiple consecutive events if the leak is not fixed.
Sensors that can detect air quality issues are available and the airline
Lufthansa
Deutsche Lufthansa AG (), commonly shortened to Lufthansa, is the flag carrier of Germany. When combined with its subsidiaries, it is the second- largest airline in Europe in terms of passengers carried. Lufthansa is one of the five founding m ...
has requested their installation, but Boeing declined to do so because of the fear of litigation from crew or passengers sickened by detectable fume events.
Health effects
The human physiological effects of fume events are yet to be fully understood by the medical community. Signs and symptoms of exposure can be misdiagnosed as other common ailments, due particularly to the delay between exposure to fumes and the onset of associated symptoms. While most aeromedical professionals believe no long-term health effects exist from fume events, some consumer and aircrew advocacy groups claim that it can cause a medically-unrecognized condition called
aerotoxic syndrome
Aerotoxic syndrome relates to ill-health effects that are claimed to be caused by breathing contaminated airliner cabin air. This condition is not an established medical diagnosis.
Potential sources of contamination
Modern jetliners have envi ...
.
Turbine engine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
oil is an irritant and contains neurotoxic chemicals such as
tricresyl phosphate
Tricresyl phosphate (TCP), is a mixture of three isomeric organophosphate compounds most notably used as a flame retardant and as a plasticizer in manufacturing for lacquers and varnishes and vinyl plastics. Pure tricresyl phosphate is a colourles ...
. The aviation industry claims that engine oil does not contain sufficient quantities of such chemicals to cause long-term damage.
However, there is some historical evidence that would seem to contradict this statement. In 1959, over 10,000 people in Morocco were paralyzed or otherwise affected after ingesting small quantities of tricresyl phosphate in their cooking oil.
Hydraulic fluid
A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoe ...
— although non-toxic in small quantities — is extremely irritating to the eyes and skin, which creates a hazard to pilots during a fume event but causes no lasting damage.
Deicing fluid Ground deicing of aircraft is commonly performed in both commercial and general aviation. The fluids used in this operation are called ''deicing'' or ''anti-icing'' fluids. The initials ADF (Aircraft Deicing Fluid), ADAF (Aircraft Deicer and Anti-i ...
has a strong smell but is not very irritating or toxic if inhaled (as opposed to the significant toxicity when ingested).
It is not mandatory for fume events to be reported in the U.S.
A ''
Los Angeles Times
The ''Los Angeles Times'' (abbreviated as ''LA Times'') is a daily newspaper that started publishing in Los Angeles in 1881. Based in the LA-adjacent suburb of El Segundo since 2018, it is the sixth-largest newspaper by circulation in the Un ...
'' analysis of NASA safety reports from January 2018 to December 2019 identified 362 voluntarily-reported fume events, in which almost 400 pilots, flight attendants and passengers received medical attention.
On 73 or more of those flights, pilots used emergency oxygen.
Four dozen pilots were impaired so far as to be unable to perform their duties.
Boeing told the ''Times'' that they believe no credible data shows that oil leaks into the bleed air stream can cause serious injuries.
By contrast, a judge who had awarded workers' compensation to a pilot who had suffered
toxic encephalopathy
Toxic encephalopathy is a neurologic disorder caused by exposure to neurotoxic organic solvents such as toluene, following exposure to heavy metals such as manganese, as a side effect of melarsoprol treatment for African trypanosomiasis, adverse ef ...
(brain damage) from a fume event condemned the airline industry's obstructionism around fume events.
See also
*
BAe 146
The British Aerospace 146 (also BAe 146) is a short-haul and regional airliner that was manufactured in the United Kingdom by British Aerospace, later part of BAE Systems. Production ran from 1983 until 2001. Manufacture by Avro International ...
References
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