CAQ overview

Since the 1950s pressurised aircraft cabin air has been drawn unfiltered from the compressor section of turbine jet engines as 'bleed air'. Therefore emissions from engine bearing chamber oil seals leads to contamination of the breathable cabin air. The synthetic jet oil lubricants contain a number of hazardous substances including the antiwear additive,tricresyl phosphate (TCP), an organophosphate (OP) which has many isomers, some of which bind to esterases in the manner of pesticides/nerve gases. The oil when exposed to the very high temperatures in the compressor generates a wide range of pyrolysed substances. Oil seals are reported to produce a noticeable fume event in the cabin in 1 per 100 flights (1%) [1]. However, to function oil seals 'weep' lubricant at varying stages of normal engine operation [2], so exposure to the oil contaminants will be occurring in normal flight. These substances are being identified at low levels in ad-hoc studies. Reports of adverse effects specifically related to the aircraft environment have continued since the early 1950s [3]. Short and long-term effects primarily involve irritant, sensitising, neurological, neuropsychological, respiratory, cardiovascular and other general effects. Exposure to contaminated aircraft bleed air, related to leaking oil or hydraulic fluids or de-icing fluids, represents a unique flight safety and occupational/public health issue that must be addressed. Solutions do exist to reduce and eliminate contamination and must be addressed at an industry-wide international level.

  1. COT (2007) COT Statement 2007/06. Statement On The Review Of The Cabin Air Environment, Ill-health In Aircraft Crews And The Possible Relationship To Smoke/Fume Events In Aircraft. London: Committee Of Toxicity.
  2. Michaelis, S. (2016) ‘Oil Bearing Seals and Aircraft Cabin Air Contamination’. Sealing Technology. April 2016
  3. Michaelis, S. (2011) PhD Thesis. 'Health And Flight Safety Implications From Exposure To Contaminated Air In Aircraft’.

CAQ consultancy

There are a range of ways in which individuals or organisations can seek expert guidance on the topic of cabin air quality. These include expert consultancy services, adapted to suit the individual, expert or organisation or a number of self-help methods as outlined below:

A. Consultancy

Consultancy service available on request:

Dr. Susan Michaelis (PhD) is uniquely qualified to provide concise and high quality support regarding the various aspects of exposure to aircraft contaminated air. These involve the following areas: Aerotoxic syndrome; overview of contaminated air issue and global actions; applicable aviation/OHS regulations; hazardous substances associated with bleed air contamination; risk and hazard assessment; fume events training and reporting requirements; available solutions; support for airlines; manufacturers; medical and legal experts; academics and scientists; unions; governments and regulators.

Rates will be provided upon request ranging from aircrew individual consultancy to consultancy available for relevant industry organisations.


B. Self help

1. Read some of the available published papers available:

Michaelis S. (2005) – Crew effects from toxic exposures on aircraft

Michaelis S. (2011) – Contaminated aircraft cabin air

Michaelis S. (2014) – Is it time to act?

Other papers

OHRCA (2009) – Exposure to Aircraft Bleed Air Contaminants Among Airline Workers – A Guide for Health Care Providers

FAA – Aerospace Toxicology: An Overview (pp 27-29)

Burdon J. (2011) – The “Aerotoxic Syndrome” — real condition or flight of fancy?

Abou-Donia M. (2013) – Autoantibodies to Nervous System-Specific Proteins Are Elevated in Sera of Flight Crew Members: Biomarkers for Nervous System Injury

Harrison V. (2015) – An emerging concern: Toxic fumes in airplane cabins
Further reading available on GCAQE health page:

GCAQE brochure

2. Watch the documentaries and film available on the cabin air issue by visiting these links:

  • Angel Without Wings (2010)
  • Welcome Aboard Toxic Airlines (2007)
  • Broken Wings (2011)
  • A Dark Reflection (2015)
  • 3. Read PhD (2010): UNSW PHd

    PhD Susan Michaelis (2011) "Health and Flight Safety Implications from Exposure to Contaminated Air in Aircraft". ISBN: 978-0-95-554377-7 Further details on how to obtain printed copy and an overview are available by clicking here.

    4. Read MSc (2016): Cranfield MSc Thesis

    Michaelis, S. (2016) "Implementation Of The Requirements For The Provision Of Clean Air In Crew And Passenger Compartments Using The Aircraft Bleed Air System", Cranfield University, UK.

    SMS Safety Case

    A unique opportunity is available for airline management to work with Dr. Susan Michaelis and global aviation hazards expert, Cliff Edwards, to develop a safety case based upon oil fumes in the cabin. The bow tie technique will be used to demonstrate mitigation of risks associated with oil fumes in the cabin. Further information can be found here.

    ICAO based fume events training

    Dr. Susan Michaelis and her team are uniquely qualified to undertake training outlined in the ICAO “Cir 344-AN/202 Guidelines on Education, Training and Reporting practices Related to Fume events”. Course can be tailored as required for aircrew, maintenance personnel, management and regulators. Further information can be found here.

    Public speaking

    Susan is in a unique position to deliver an informative content driven global approach to an activity which touches almost all of us, combined with her inspirational personal story of overcoming adversity. We all take air travel and safe arrival at our destination for granted. However Susan’s two decades unravelling of one of the airline industry’s most ignored issues will capture your attention and is a message you need to hear before you next fly.

    Susan’s message is unique and one that corporate managers, safety professionals through to the travelling public will be left thinking about.

    Presentation topics:
    1. Susan’s journey: Pilot to global expert
    2. Aircraft contaminated air: You can make a difference
    3. Corporate regulation?
    4. History repeats itself

    Find out more and book Susan

    Legal expert consultancy

    Dr. Susan Michaelis’s expertise and knowledge on the aircraft contaminated air issue is second to none. Her in-depth knowledge of almost every aspect will assist your case. Do not make the mistakes others have made and take on a case unprepared and unaware of the key issues and supporting evidence. The evidence is clearly available and is essential knowledge for anyone involved in contaminated air cases.

    Dr. Michaelis’s background as a commercial pilot, PhD qualifications on the contaminated air topic and related expertise, along with her in-depth knowledge of all the key parties and their role, make her unique in this field.

    As identified by the Lawsuit Coach (, ensure you are undertaking a ‘winnable’ case by being prepared.


    Recent conferences

  • SAE - E31B - Ultrafine particle measurements in aircraft - Cologne, Germany (January, 2019)
  • SAE - E31B - Air monitoring studies - Cologne, Germany (January, 2019)
  • International Committee of Occupational Health (ICOH) - Dublin. (May, 2018)
  • Iceland Flight Safety Symposium: Reykjavik. (2018)
  • SAE-AC9 Florida. (April, 2018) (34 Mb)
  • International Fluids & Sealing Conference (2018)
  • Oil sealing: Int Aircraft Cabin Air Conference, Imperial College London (September, 2017)
  • 25th EPICOH Conference - Epidemiology in Occupational Health (2016)
  • International Fluids & Sealing Conference (2016)
  • Electric & Hybrid Aerospace Technology Symposium (2015)
  • EU Commission: Occupational Diseases in the EU: New/Emerging Workplace Risks Conference (2013)
  • Aerospace Medical Association Annual Conference: (2011)
  • Technical papers

  • Michaelis, S. (2018) Aircraft Clean Air Requirements Using Bleed Air Systems. Engineering, 10, 142-172. or download the .pdf
  • Michaelis, S. (2018) An update on aircraft oil bearing chamber sealing Sealing Technology, March 2018.
  • Michaelis S. (2018) 1718c. Aerotoxic syndrome: a new occupational disease? (adverse health effects experienced by aircrew exposed to aircraft contaminated air) Abstract: Presentation at ICOH - International Congress on Occupational Health, Dublin, May 2018: Accident Prevention. Occup Environ Med 2018;75:A15 or download the .pdf
  • Howard CV, Johnson DW, Morton J, Michaelis S, Supplee D, et al. (2018) Is a Cumulative Exposure to a Background Aerosol of Nanoparticles Part of the Causal Mechanism of Aerotoxic Syndrome? J Nanomed Nanosci: JNAN-139 or download the .pdf
  • Michaelis S. (2018) Bearing chamber sealing and the use of aircraft bleed air. Published and Presented at BHR Group’s 24th International Conference on Fluid Sealing, 7 – 8 March 2018; Manchester, UK
  • CV Howard, S Michaelis, A Watterson. (2017) The Aetiology of ‘Aerotoxic Syndrome’- A Toxico-Pathological Viewpoint. Open Acc J of Toxicol. 2017;1(5): 555575 or download the .pdf
  • Michaelis, S. (2017) The Inapplicability of Exposure Standards
  • Michaelis, S et al (2017) Aerotoxic Syndrome: A New Occupational Disease - Public Health Panorama, World Health Organization. Volume 3, Issue 2, June 2017 / Link to the World Health Organization Journal, Public Health Panorama. June 2017
  • Michaelis, S., Burdon, J., Howard, CV (2016) Poster. Aerotoxic Syndrome: A new occupational disease? Ramazzini Days, Carpi, October, 2016
  • Michaelis, S. (2016) O27-3. Aerotoxic syndrome – fact or fallacy? Abstract: Presentation at ICOH - International Congress on Occupational health: Epidemiology. Barcelona, August 2016: Chemical and Physical Exposures
  • Michaelis, S. (2016) Oil bearing seals and aircraft cabin air contamination - Sealing Technology. April 2016
  • Michaelis S. (2014) Selected key government and industry CAQ studies to 2014
  • Michaelis, S. (2014) Is it time to act? - Journal of Biological Physics and Chemistry. 14 (2014) 133–135
  • Michaelis, S. (2012) Contaminated Aircraft Cabin Air - Journal of Biological Physics and Chemistry. Vol. 11 No 4 12/2011. pp 132-145
  • Best, R., Michaelis, S. (2005) Aircraft air quality malfunction incidents: Design frequency and severity of toxic effects. In: Hocking, M., editor, Air Quality in Airplane Cabins and Similar Enclosed Spaces. Handbook of Environmental Chemistry 4: 249-266
  • Winder, C., Michaelis, S. (2005) Crew effects from toxic exposures on Aircraft. In: Hocking, M., editor, Air Quality in Airplane Cabins and Similar Enclosed Spaces. Handbook of Environmental Chemistry 4: 229-248
  • Winder, C., Michaelis, S. (2005) Aircraft air quality malfunction incidents: Causation, regulatory, reporting and rates. In: Hocking, M., editor, Air Quality in Airplane Cabins and Similar Enclosed Spaces. Handbook of Environmental Chemistry 4: 211-228
  • Michaelis, S. (2003) A Survey of Health Symptoms in BALPA Boeing 757 Pilots - The Journal of Occupational Health and Safety; Australia and New Zealand 19: 253-261
  • Cox, L., Michaelis, S. (2002) A survey of health symptoms in BAe 146 pilots - The Journal of Occupational Health and Safety; Australia and New Zealand 18: 305-312
  • Books

    Michaelis, S. (2011) PhD Thesis - "Health and Flight Safety Implications from Exposure to Contaminated Air in Aircraft ". ISBN: 978-0- 95-554377-7
    Available to purchase in hardback: (690 pages, 2kg) - £135 plus p&p - To request all inclusive quote email

    or download the .pdf

    Michaelis, S. (2007) "Aviation Contaminated Air Reference Manual". ISBN 9780955567209
    Available to purchase in hardback: (844 pages, 2kg) - £110 plus p&p - To request all inclusive quote email