Lufthansa is working on initiatives to reduce cabin fume events on its fleet of Airbus A380s. The measures include alterations to the Rolls-Royce Trent 900 engines, procedural changes and better surveillance of cabin air quality.

The airline says it has experienced an unusual number of cabin fume events on its A380 services, particularly when outbound from Singapore. In the events, cabin crew and passengers reported unusual odors in the cabin, but the problems did not cause health problems, the airline states. Because many of the events were reported on return flights from Singapore, the airline suspects climatic conditions may play a role in the causal chain.

Cabin air is supplied through the bleed air system with air taken in from inside the engines. The industry says that the system is safe, but there also have been reports--and even lawsuits—filed by cabin crew and pilots who claim to have suffered serious health problems from toxic fumes. The only passenger aircraft that does not use the bleed air system is the Boeing 787. Other types that have been linked to more frequent fume events include the BAe-146 and the A340-600.

Lufthansa has started to install protective covers in front of the bleed air inlets inside the Trent 900s to keep fumes from being circulated throughout the cabin. TCPs or tricresyl phosphates, toxic substances added to kerosene to ensure a mostly consistent state, are suspected of being linked to the more serious fume events, although a 2011 Cranfield University study concluded that fume events in aircraft cabins do not cause danger for passengers and crew.

Nevertheless, the airline also proposes a new procedure where the bleed air system is turned off during engine startup, when often small quantities of leaked kerosene are burned off. The procedure still awaits approval by Airbus, Rolls-Royce (R-R) and the European Aviation Safety Agency.

Separately, the carrier has commissioned the development of sensors that will be installed in the cockpit. They will record concentrations of substances in the cabin air once pilots notice an unusual odor. But given the lack of scientific certainty about what quantities are dangerous, the sensors will not be equipped with a warning mechanism. Lufthansa says development is at an “advanced stage,” but cannot say when the sensors will be ready to use.

R-R says in a statement, “We can confirm that we are working with Lufthansa on a specific cabin odor issue the airline has experienced on a small number of A380 flights. A solution to this issue has been identified and is being implemented.” The engine maker also says it is “working with a number of aviation regulatory and academic organizations to help in the understanding and prevention of cabin odor events.”

Singapore Airlines, another Trent 900 operator, says it is “checking internally any bleed air issues on the A380 as reported, but at this point we are not aware of similar incidents.”

Lufthansa is grappling with the public fallout from a December 2010 near accident linked to fumes on a Germanwings Airbus A319. Germany’s accident investigation office BFU released a preliminary report into the case last month. The aircraft was on a scheduled flight from Vienna to Cologne/Bonn in severe winter weather and was delayed for several hours before departure because the airport was closed. The aircraft was deiced immediately before departure. There was no incident during cruise flight, but on final approach, the two pilots noticed an unusual odor in the cockpit. Just before the final turn on the extended runway center line and about 12 miles outbound from Runway 14L, the first officer complained that he was feeling severely sick. His arms and legs began to feel numb and he put on the oxygen mask. The captain experienced similar, albeit not as serious, symptoms and also put on the mask. He said he was seriously limited in his ability to perform the routine landing preparation and unable to determine the cause of his condition. He told the first officer, who says he could neither follow nor comprehend what was happening, that he would land even though they had not completed all pre-landing duties upon passing the 1,000 ft. mark. He added that he did not feel fit to perform a go-around and attempt another approach.

After landing, the two pilots forgot to turn on the APU and retract the flaps, among other duties. They were then sent to a local hospital, where the first officer was found to have two unusual blood parameters. He was unfit to fly for six months following the incident.

Germanwings technicians checked the aircraft and noticed the odor in the cockpit. They identified it as deriving from deicing fluid and ruled out fuel. Engine checks did not reveal any unusual findings and the aircraft returned to service a day later.