|At high altitudes, the air outside the aircraft is not compatible with life and it is therefore necessary to produce an environment within the cabin which is compatible with personal comfort and safety. Although the cabin oxygen content is a little less than that at sea level, the body’s mechanisms in healthy individuals can make appropriate adjustments. |
The air pressure in the cabin is increased relative to that outside the aircraft by using some of the air which has been compressed in the engines. Up to half the cabin air is recirculated and mixed before being distributed through the cabin.
This air is mixed and passed through high efficiency filters, which remove bacteria, viruses and particulate material. These filters are similar to those used in hospital operating theatres. The total volume of cabin air is exchanged every two to three minutes compared with every five to ten minutes in most air conditioned buildings. There is no evidence that the pressurised cabin makes transmission of disease more likely. Simple viral infections may be transmitted due to the proximity of individuals who may have such conditions.
There has been much publicity surrounding substances that may enter the air conditioning from the engine during the process of cabin air replacement.
Studies such as the European CabinAir project have shown that normally the levels of chemical and biological contaminants in aircraft are less than in many work environments such as office buildings.
There are however occasional bad smells or 'fume events' during flights, and these have been reported on a number of aircraft types which are in use around the world. Reports to the Civil Aviation Authority (CAA) show that sometimes one pilot reports a bad smell and the other detects nothing. An unpleasant smell is undesirable but does not necessarily harm health. Conversely carbon monoxide has no smell yet kills people in the home every year.
Some pilots who have experienced these events report a variety of short or long term symptoms or ill health. But it is not certain that these symptoms are work related.
The independent Committee on Toxicity (COT); a panel including toxicologists from various universities, completed an extensive review of evidence in September 2007 and concluded that the evidence available did not establish a link between cabin air and pilot ill health. However, the COT and indeed the House of Lords Select Committee on Science and Technology recommended research to study the components of cabin air. The research was led by Cranfield University and the report, published on 10 May 2011, is available on the following link:-Cranfield University Report
For further information see:
Department for Transport, Cabin Air Quality