Cabin Fumes from Non-Fire Sources

Cabin Fumes from Non-Fire Sources

Description

Fumes from various non-fire related sources may sometimes be experienced within the cabins of passenger aircraft.

Sources

Most modern passenger aircraft are equipped with pressurised, climate-controlled cabins. In spite of the aircraft designers’ intentions, unwanted fumes frequently permeate the interior of the aircraft. Open doors and hatches as well as certain on-board sources can introduce fumes to the cabin environment. However the usual path of entry for fumes is via the aircraft pressurisation and air conditioning systems.

The majority of passenger aircraft utilise bleed air from the engine or auxiliary power unit (APU) to pressurize and heat or cool the aircraft cabin. As a consequence, any contaminants introduced into the engine/APU compressor prior to the point from which the bleed air is extracted may result in the appearance of corresponding fumes in the passenger cabin and flight deck.

Accidents and Incidents

Cabin air contamination

On 9 February 2023, a Boeing 777-200ER was en-route near Marseille when the cabin crew observed smoke coming from a rear galley oven which was spreading into the rear passenger cabin. After an immediate initial response and use of multiple Halon Fire extinguishers, the smoke ceased after about 20 minutes but the fumes remained. Although this meant no ongoing emergency existed, some cabin crew and passengers had experienced breathing difficulties and it was decided to return to Amsterdam. The cabin crew response to the situation was subsequently assessed as contrary to applicable procedures and relevant cabin crew training seemingly inadequate.

On 6 June 2023, a Boeing 717-200 was on base leg about 10 nm from Hobart when chlorine fumes became evident on the flight deck. As the aircraft became fully established on final approach, the Captain recognised signs of cognitive impairment and handed control to the initially unaffected First Officer. Just before touchdown, he was similarly affected but was able to safely complete the landing and taxi in. The same aircraft had experienced a similar event two days earlier with no fault found. The Investigation determined that the operator’s procedures for responding to crew incapacitation in flight had been inadequate.

On 15 December 2019, an Airbus A330-200 turned back to Sydney shortly after departure when a major hydraulic system leak was annunciated. The return was uneventful until engine shutdown after clearing the runway following which APU use for air conditioning was followed by a gradual build up of hydraulic haze and fumes which eventually prompted an emergency evacuation. The Investigation found that fluid leaking from ruptured rudder servo hose had entered the APU air intake. The resulting evacuation was found to have been somewhat disorganised with this being attributed mainly to a combination of inadequate cabin crew procedures and training.

On 5 August 2019, an Airbus A321 crew declared a MAYDAY immediately after clearing the landing runway at Valencia when a hold smoke warning was annunciated. An emergency evacuation was completed without injuries. This warning followed “white smoke” from the air conditioning system entering both the passenger cabin and flight deck in the four minutes before landing which had prompted the pilots to don oxygen masks. The Investigation found the white smoke was the direct consequence of an oil leak from the right engine as a result of the misalignment and breakage of a bearing and its associated hydraulic seal. 

On 6 March 2018, smoke was detected coming from flight deck and passenger cabin air conditioning vents of an en-route Bombardier DHC8-400. A MAYDAY was declared to ATC but the prescribed response effectively cleared the smoke and no emergency evacuation on landing was deemed necessary. The Investigation found that the smoke was caused by oil leaking into the air conditioning system due to a failed right hand engine seal. The operator subsequently began to implement a recommended engine modification and adopt a system provided by the engine manufacturer to proactively detect such oil leaks before air conditioning systems are contaminated. 

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