Better air in planes - at last!
A series of technical changes is making it possible to improve the quality of cabin air in airplanes which until now has been invariably dry and poor in oxygen. The reason: the air was derived from the jet engines. This so-called "bleed air" is mixed with fuel and combusts and reaches such high temperature and pressure that it then has to be cooled and filtered through high-efficiency particulate air (HEPA) filters. However, HEPA is relatively recent and 25% of the US commercial fleet is not equipped. In existing planes, the air is compressed to the same pressure as approximately 2500 m above sea level. The fact that planes are made up of aluminium components riveted together is an obstacle to higher air pressure which would cause too much wear and tear to the fuselage. And higher humidity rates would cause corrosion, consequently the air humidity rates are at about 4% and the only humidity comes from the occupants' breath. In the new Boeing 787, the air will be vented directly through inlets on the lower part of the plane and will not go through the engines. An electrical system, driven by power generated from the engines, will humidify the air to 15% humidity, which is possible as the plane's fuselage is made of non-corrosive composite material. The air can also be compressed to pressures similar to those at 1900 m above sea level. The system is also HEPA-equipped and has an additional filter to remove volatile organic gases due to hand wipes, cologne, vinyl, etc. that build up inside the plane making some passengers feel ill. The innovative system promoting passenger comfort is considered by airlines as an important consideration when buying a plane and 400 aircraft are now on order.