Problems with aircraft air quality include inadequate ventilation, a cabin that is either too hot or too cold, low pressure (oxygen), ozone exposure, and fume events. A fume event is what happens when either engine oil or hydraulic fluid contaminates the ventilation air flow. Usually, there is no smoke or haze – “just” an unusual, unpleasant smell coming from the vents. There are other types of fumes, too, such as electrical, engine exhaust, and deicing fluid. But this page is dedicated to oil and hydraulic fluid fumes because those are reports we receive most frequently, and they have the potential to cause serious health impacts and compromised flight safety.
Quick links for practical help
IFALPA updates its fume events position paper
In October 2023, the International Federation of Airline Pilots Associations’ updated its Cabin Fumes position paper and briefing leaflet. The global pilots’ association calls for standardized reporting and training of fume events, bleed air filters and sensors, a standardized medical protocol, less toxic oils, and stronger regulatory enforcement.
European standard-setting body (CEN) publishes TR17904
In November 2022, the Center for European Normalization published Technical Report (TR) 17904 which is a comprehensive collection of best-practice recommendations to prevent exposure to oil and hydraulic fluid fumes onboard aircraft. You can purchase it across Europe. It is an important resource for manufacturers, airlines, and regulators. The best-value purchase option is through LVS for 29 euros. To buy a copy of CEN TR17904, register with your email address on the LVS website. Then, enter “17904” in the search box on this page and then “add to cart.”
Examples of fume events in the news --
LA Times publishes in-depth investigative news piece: Highlights the ways in which fumes can compromise flight safety (Dec. 17, 2020); also, LA Times published two shorter companion articles, one describing how the Times conducted its investigation and the other describing the most common odor descriptors for onboard oil/hydraulic fumes
More reports of “dirty socks” fumes onboard: NBC news segment describes documented fume events that sent crewmembers to hospital and potentially compromised flight safety (Aug. 16, 2017)
Flight crew members say toxic air in plane cabin harmed their health: Good Morning America segment raises travelers’ awareness about the potential for exposure to oil fumes inflight (Nov. 22, 2016)
“Mystery illness” no so mysterious: Fume event reported on British Airways flight 286, Oct. 24, 2016. Captain told air traffic control that the diversion was necessary because of a “fume event” (listen to recording of exchange between ATC and captain, starting at 3:10) Flight scheduled from SFO-LHR; diverted to YVR. “Unusual smell” reported during cruise, some of the cabin crew felt unwell, emergency landing, all 25 members of crew treated upon landing. One passenger said it smelled as though someone took their shoes off. Another passenger said that medical attention had been recommended, but the airline would not cover the cost, quoted at $800 per person. In January 2017, a local news group reported that the investigation is ongoing after a leaked report described the effects on the crew.
Examples of flight safety issues --
Aerospace journal publishes about NTSB and turboprop crashes: Open access article which reviews 1980s NTSB investigation into “hypothesis” that aircraft crashed when pilots were overcome by oil fumes and provides more recent examples of compromised flight safety.
IFALPA publishes Cabin Air Quality documents: The International Federation of Airline Pilots’ Associations emphasizes the potential flight safety hazards posed by inflight exposure to smoke/fire/fumes, and recommends constructive engineering and training solutions. (2023 documents listed above. Also: Dec. 2018 position statement, Dec. 2018 five page briefing leaflet, June 2013 position statement, Feb. 2013 safety bulletin)
ICAO publishes Circular 344: The International Civil Aviation Organization published a circular that provides guidance on education and training for airline workers to recognize and respond to oil fumes onboard, given the potential for flight safety to be compromised when crews breathe oil fumes onboard. (Nov. 2015)
Summary of compromised flight safety documents and investigative reports: Summary of a sample of published documents that describe compromised safety (confirmed or suspected) coincident with crewmember exposure to engine oil-contaminated air onboard aircraft (rev. 2016). The earliest reference listed regarding exposure to “hot oil fumes” and the potential for flight safety to be compromised is an aviation medicine textbook published in 1939.
FAA recognizes pilot exposure to oil fumes as “unsafe condition”: Aviation regulator mandates inspections and “corrective actions” in the air supply system on one aircraft type to prevent crew exposure to engine oil fumes. The presence of oil fumes in the air supply system is not unique to this one aircraft type because all commercial aircraft (except for the B787) use unfiltered engine bleed air for ventilation, and all aviation engines are lubricated with chemically-similar oils.
Swedish air accident authority (SHK) investigated near-crash on commercial flight during descent into Malmo, Sweden: Pilot impairment and temporary incapacitation was documented coincident with them breathing oil fumes during the descent phase of flight; view video footage of the captain from that flight.
Sample of published medical/regulatory articles of interest --
Selection of historical clips and information --
2012: International Transport Workers’ Federation releases educational film -- The ITF is a global organization with 690 member unions representing over 4.5 million transport workers in 153 countries, including AFA-CWA. “Contaminated Air: What You Need to Know” was released in 2012 to help educate airline workers about the potential for exposure to oil fumes on aircraft, including practical steps to take if fumes exposure is either suspected or confirmed
2011: Published review of fume events at one major US airline: Review includes description of impact of exposure to smoke/fumes on crew health and flight safety.
Mar 2011: UK Department for Transport releases report into flight deck air quality measurements onboard 100 UK flights, conducted by researchers at Cranfield University (Part I, Part II). Report concludes no problem with aircraft air supply contamination. Read counterpoint here.
March 2009: ASHRAE President sent this letter to the heads of FAA and its European counterpart, EASA, urging the two agencies to investigate and determine the requirements for bleed air monitoring and solutions to prevent bleed air contamination with engine oil. This action was unanimously approved by members of the ASHRAE Aircraft Air Quality committee (SSPC-161P) in attendance at the Jan. 2009 meeting
Sept 2008: Australian aviation regulator, CASA, has convened an independent Expert Panel on Aircraft Air Quality (EPAAQ). The EPAAQ has a broad mandate, covering both safety and occupational health and safety matters. The panel will review the evidence and prepare a report with recommendations. The report is expected to be delivered by the first quarter of 2010. The CASA website states that “Individuals and groups representing aircrew members have raised concerns about the possibility of low level chronic exposure to contaminants in aircraft cabin air leading to potential long term health effects. Some flight crew have reported a variety of symptoms that they have associated with cabin air quality. The evidence based relationship between cabin air exposures (either in normal operations or following incidents) and ill health in aircraft crews has been difficult to ascertain. The expert panel will: review existing literature on cabin air quality; seek submissions from interested parties who wish to provide evidence for consideration by the panel; and review the evidence and submissions and prepare a report with recommendations.“
Dec. 2007: At long last, the ASHRAE Aircraft Air Quality Standard 161-2007 has been published. It is a voluntary standard but represents the best consensus between industry and crewmember unions, and it includes provisions to prevent hot cabin conditions, limit exposure to oil fumes and pesticides, require gaspers in crew work areas, and more. The current version of the ASHRAE standard (2018) and its companion guideline (2021) are available as “read-only” files online.
Jan 2007: Australian Transportation Safety Board releases report on pilot incapacitation, citing exposure to toxic fumes as the second-leading cause.
April 2007: UK Air Accidents Investigation Branch issues incident report regarding oil fumes in flight deck and a necessary diversion. Report recommends that EASA and the FAA require a flight deck detection and warning system for oil smoke/mist.
March 2006: Swiss Transportation Safety Board incident report concludes that exposure to oil fumes compromised ability of the copilot during approach and landing, that the captain had not donned his oxygen mask, and that the aircraft had a history of odors/fumes that had not been addressed.
Aug 2005: OSHA succumbs to pressure to settle case with ExxonMobil (see Aug 2004). Crewmembers and their doctors need to understand that the current "warnings" that ExxonMobil has published ignore the health risks associated with inhalation of engine oils and ignore the toxicity of meta and para isomers of the neurotoxic tricresylphosphates. Bottom line: if you are a hen, drink large volumes of engine oil, and are only worried about short-term effects to your peripheral nervous system, then the current warnings on the ExxonMobil labels and data sheets are okay.
Aug 2004: OSHA cites engine oil manufacturer Crewmembers and passengers can suffer neurological damage after exposure to aerosolized oil mists in the cabin and cockpit of commercial aircraft. In Feb 2004, AFA filed a complaint with OSHA, stating that ExxonMobil had, without basis, watered down the warnings about nervous system damage on the labels and Material Safety Data Sheets of its jet engine oils. ExxonMobil was relying on research that was incomplete and irrelevant to the exposure conditions and symptoms experienced by crewmembers and passengers.
June 2004: FAA acknowledges that exposure to pyrolyzed engine oil can cause impairment of the operational skills and abilities of the flightcrew, which could result in reduced controllability of the airplane.” Policy applies to BAe146 aircraft, but all commercial aircraft have bleed air system and all use chemically similar oils
2004: Aviation Organophosphate Information Site (AOPIS) releases documentary video on aircraft air supply contamination and the serious health effects it can cause among flight attendants, pilots, and passengers
July 2003: AFA review of FAA response to 2002 National Research Council committee recommendations on aircraft air quality In January 2002, the NRC Committee on Air Quality in Passenger Cabins of Commercial Aircraft released a report that detailed its year-long assessment of air quality on commercial aircraft, including ten recommendations. In response, the FAA acknowledged that it “has not kept pace with public expectation and concern about air quality and does not afford explicit protection from particulate matter and other chemical and biological hazards.” To date, though, the FAA has still failed to take any meaningful action.
June 2003: Aircraft air quality: What's wrong with it and what needs to be done AFA submission to the Aviation Subcommittee of The Transportation & Infrastructure Committee, US House of Representatives. Association of Flight Attendants, AFL-CIO. Also see passenger submission to Aviation Subcommittee hearing
June 2003: Timeline of events related to the introduction of ozone exposure standards on commercial aircraft, 1976-1983 Association of Flight Attendants, AFL-CIO
Feb 2003: Position paper of the International Task Group on Aircraft Air Quality Labor group under the International Transport Workers' Federation concerned about aircraft air quality; members represent cabin crew in the US, Australia, Canada, Europe, Mexico, and South America.
Jan 2003: FAA issues a recommendation (not a regulation) that aircraft passengers not be left without ventilation for more than 30 minutes. We are unaware of action by the airlines to implement this recommendation as policy.
Aug 2002: UK regulator issues recommendations to airlines in light of increased number of reports of pilot incapacitation Oil leaking from the engines or APU into the air supply systems cited as "the most probable source" of the reports, and state that reducing occurrences of oil contamination will also reduce the risk of flight crew incapacitation.
Jan 2002: One page synopsis of NRC report on aircraft air quality Association of Flight Attendants, AFL-CIO
Nov 2001: Swedish aviation authority (SHK) investigation into air quality incident onboard a commercial flight Nov 1999 during which the captain was incapacitated inflight when exposed to oil fumes. The first officer and the flight attendants also reported symptoms.
Oct 2000: Air Safety and Cabin Air Quality In the BaE146 Aircraft Official report outlining two-year bipartisan Australian Senate inquiry into complaints of ill health and compromised aviation safety on the BAe146 aircraft
1956: Early recognition of oil fumes “problem” US Air Force biochemist/researcher publishes a paper which recognizes “the problem” of exposure to oil fumes on commercial and military aircraft.
Some FAA regulations and recommendations --
Search 14 CFR Parts 25 and 121 for the following current and historical regulations:
14 CFR 25.831 – Design standard for ventilation, carbon dioxide, carbon monoxide
14 CFR 25.832 – Design standard for ozone
14 CFR 25.841 – Design standard for cabin altitude and depressurization limits
14 CFR 25.1309(c) – Flight deck must provide warnings to crew of unsafe system operating conditions
14 CFR 25.1322 – Flight deck displays must provide pilots with warnings, alerts, and cautions
14 CFR 121.578 – Operating standard for ozone (not enforced with measurements)
14 CFR 121.219 – Operating standard that cabin be "suitably ventilated," plus an operating limit for carbon monoxide (not enforced with measurements)
Airworthiness Directive 2000-15-17 (required): Only applicable to certain aircraft, intended to prevent leaks in particular hydraulic fluid lines that can result in smoke and odors in the passenger cabin or cockpit (Effective Sept 12, 2000)
Advisory Circular 121-35: Recommend that passengers not be left without ventilation for more than 30 minutes (Jan 16, 2003)
Advisory Circular 121-36: Information on possible allergic reactions (peanuts, etc) in-flight (Dec 31, 2002)
Advisory Circular 120-38: Guidance for airlines to comply with ozone regulations (Oct 10, 1980)