ICAO Circular 344

Cabin safety bulletin 13 – Management of odours, smoke and Reporting Practices related to Fume Events fumes during flight

The Australian Civil Aviation Safety Authority (CASA) has published a specific safety bulletin on the problem of contaminated cabin air (Nov. 2018)

The Cockpit Association would like to thank CASA for its support and for providing the document. 

The background of the publication is the high number of more than 1000 incidents between 2013 and 2017 in Australia that are related to fire, smoke or odour. 

"In some instances, fume events may impair crew members and could potentially impact the safe operation of the aircraft. Cabin crew members should be able to recognise, characterise, respond to, and report fume events."

The Bulletin is intended to help airlines and cockpit and cabin crews to prepare for dealing with Smell events.

"This bulletin provides information and guidance which may be considered in preparing for these events, reviewing strategies to mitigate risks, facilitating standardised reporting and comprehensive data collation for trend analyses."

We would like to introduce some important points from the bulletin. The complete document can be downloaded below.

" Operators should ensure cabin crew training encompasses the following:

  • sources and types of on-board fumes
  • odour descriptors to recognise the presence of oil and hydraulic fluid fumes
  • potential for impairment
  • procedures to apply in fume events
  • reporting of fumes events. ." 

"Fumes in the cabin and/or flight deck can be sourced to:

  • Ventilation air supply system. This system can distribute contaminants such as de-icing and/or anti-icing fluid fumes, electrical fumes, engine compressor wash fumes, engine oil fumes, exhaust fumes, fuel fumes, hydraulic fluid fumes, recirculation fan fumes. Oil fumes from the engines, APU or the environmental control system may also contaminate the aircraft air supply system. In such instances, the oil fumes may contaminate the downstream ventilation ducting and the air carried through those ducts to the cabin, flight deck or both. 


  • "Sometimes oil fumes do not smell like oil and may typically be described as mouldy/musty or dirty socks. Hydraulic fluid often has a distinctive and recognisable odour that is described as acrid/unpleasant/pungent. Odour is subjective and olfactory fatigue reduces a person’s ability to detect odours over time. "

and further

  • "Of all of these potential contaminants, particular concerns have been raised regarding the negative impact on flight safety when crew members are exposed to oil or hydraulic fluid fumes or smoke and experience acute symptoms in flight (ICAO, 2015)."

The CASA demands:

  • "Operator procedures should also address the means by which the effects of fume events will be minimised for all aircraft occupants."


  • "Cabin crew members should be trained to recognise and respond to fume events[...]"

In addition to the crew training, training of the "managerial personnel" is also required:

  • "Managerial/supervisory personnel should receive an orientation to fume event causality and the potential impact on flight safety. The depth of training may be commensurate with the management role."

It is also recommended to establish standard reporting forms in flight operations.

  • "Standardised smoke and fumes reporting forms should be developed and/or reviewed by a cross disciplinary team (for example, flight operations, engineering, cabin crew, safety departments) in order to validate user experience and verify data collection effectiveness."


  • flight and report details
  • smoke or fire information, as appropriate
  • fume information (including the nature and apparent source of fumes)
  • other observations
  • symptoms/reactions
  • maintenance follow-up and information.

You can download the official CASA document and a report sample here: