Toxic air in the aircraft cabin: What are fume events?
Concerns over the safety of cabin air are back in focus after a new report highlighted an uptick in reported “fume events” on commercial aircraft.
According to the findings of a Wall Street Journal investigation, thousands of incidents have been logged with the US Federal Aviation Administration (FAA) since 2010, with reports accelerating in recent years.
At the centre of the problem is the way air is supplied to the cabin. Most commercial aircraft – except the Boeing 787 – rely on bleed air drawn directly from engines, to provide air conditioning.
Based on an extensive review of FAA and NASA records, research papers and industry interviews, the Wall Street Journal alleges that both manufacturers and airlines have downplayed the health implications.
What are fume events and why do they happen?
A fume event refers to the contamination of cabin air with chemical fumes, smoke, or other pollutants, usually originating from an aircraft’s engines or auxiliary power unit.
In most modern aircraft, outside air is channelled into the cabin through the engines as part of the bleed air system.
If seals or other components fail, fumes or contaminants can enter the cabin and cockpit air supply.
These fumes can carry potentially harmful substances.
What is the impact of fume events?
Symptoms reported by crew and passengers during such events range from headaches and dizziness to respiratory issues and, in some cases, longer-term health concerns.
When a fume or smoke event occurs, the affected aircraft is typically withdrawn from service while the incident is investigated using a smoke event checklist, and in some cases by a dedicated airline maintenance team.
To assist with pinpointing the source, specialised diagnostic equipment can also be deployed.
Most modern aircraft are now fitted with HEPA filters, which help to rapidly clear odours or smoke from the cabin environment.
These filters are standard equipment on newly manufactured aircraft and help to keep cabin air clean during regular operations.
How big is the problem?
The frequency of such incidents is difficult to quantify precisely, as many go unreported or are dismissed as minor.
However, data uncovered by the Wall Street Journal suggests a noticeable rise in reported cases over the past decade.
While manufacturers stress that existing systems meet regulatory safety standards, critics argue that the industry has not adequately addressed the potential risks.
The introduction of non-bleed-linked cabin air supply systems, such as on Boeing’s 787, shows that alternatives are possible, but cost and fleet uniformity remain key barriers to broader adoption.
What is the response from crew?
Organisations representing crew have long argued for tougher rules to tackle bleed air contamination.
The European Cabin Crew Association (EurECCA) has called for airlines, manufacturers, and the EU Aviation Safety Agency to immediately implement new cabin air quality standards.
After the European Committee on Standardisation (CEN) published a technical report in 2022 including recommendations on how to prevent exposure to fumes through improvements in the design, maintenance, and operation of aircraft, EurECCA President Annette Groeneveld said: “Fume events put the health and safety of all people on board of an aircraft at risk.
“What we need now is a fast, comprehensive, and profound implementation of the proposed measures to ensure a safe and healthy environment for our crews and the passengers.”
What impact do fume events have?
There are numerous incidents of suspected fume contamination over recent decades.
On 2 January 2020, for example, a British Airways flight from Athens to London experienced a serious in-flight incident linked to a suspected fume event.
As the aircraft approached Heathrow, the first officer became incapacitated at the controls, prompting the captain to issue a Mayday call to air traffic control.
The aircraft landed safely, and the incident was later attributed to contaminated air entering the cockpit. There have been many other such reports.
However a recent scientific study of fume events concluded that “fume events are not associated with significant clinical consequences for cabin and cockpit crew”.
A 2020 EASA study also noted that “persistent data gaps prevent decisive conclusions concerning the possible relationship between health-related problems and exposure to chemicals in aircraft cabin air during reported smell events”.
