|Modern commercial aircraft fly at altitudes where the atmosphere outside the aircraft is not able to support human life. All aircraft therefore have systems which ensure that cabin air provides adequate oxygen levels for breathing, as well as removing contaminants and maintaining a comfortable temperature. |
On almost all large commercial aircraft the cabin air supply is provided by using some of the outside air which has been drawn into and compressed in the engines. This air, which has very low levels of moisture (humidity), passes through air-conditioning units before being distributed throughout the cabin. The system is automatically controlled to maintain the cabin air pressure at a safe level.
Up to half the cabin air is re-circulated and passes through high efficiency filters, similar to those used in hospital operating theatres, to remove bacteria, viruses and other particles before it is mixed with outside air from the air-conditioning units. Re-circulation helps to increase the moisture level in the cabin air and, because of the use of the high efficiency filters, does not lead to an increased risk of infection. There is more information about the risk of catching an infection on board on our website.
In recent years some people have expressed concerns about possible health effects due to exposure to contamination of cabin air, particularly contamination of the air drawn from the engines by engine oil. A considerable amount of research has been undertaken in a number of countries and in 2007 the Department for Transport asked the independent Committee on Toxicity to conduct a review of the evidence.
The Committee concluded that the evidence available did not establish a link between cabin air contamination and ill health but made some recommendations for further research. Following additional Government funded research, the Committee reviewed the latest research and published their conclusions in December 2013. The Committee members thought it unlikely that the long-term illnesses that have been reported are linked to a toxic effect of cabin air contamination. You can read the full report on the Committe's website.