Normally, people don’t think much about the air they breathe. Humans are naturally adapted to breathe air found at sea level and up to the summits of all but the highest mountains. It takes a smoggy day to even notice a problem with air quality.
It’s a different story for airplane designers. Commercial airliners fly at altitudes that dwarf Everest, and the atmosphere up there is radically different from anything living creatures are equipped to survive. Considerable thought and effort has gone into making the interior atmosphere of an airline cabin safe and comfortable.
Cabin Air Comes from Engines
Without cabin air pressurization, airline passengers would quickly fall unconscious due to the lower air pressure that exists at cruising altitude. To retain a higher pressure than the outside atmosphere, the cabin has to be airtight. With hundreds of people breathing the same air, the air supply has to be replenished too.
Fortunately, airplanes already come equipped with fans powerful enough to sufficiently compress the needed quantity of air. These are the turbofans inside the engines. A small amount of the air that passes through the engine turbofans is redirected to an intercooler and air packs which reduce the temperature down to a level comfortable for passengers.
Cabin Air is Clean
Airline cabin air has a notorious reputation for being of poor quality, but in fact airplanes are designed to provide very clean air for their passengers.
The air at 30,000 feet is completely sterile, which is something that few hospitals can boast. Cabin air is highly filtered (94 to 99.9 percent capture of microbes) and completely refreshed every two minutes, which is a rate well above the average for crowded interior spaces on the ground.
Cabin Air Pressure Incidents Are Rare
Airline passengers have unavoidably heard the flight attendant say the words, “In the unlikely event of a loss of cabin pressure . . . . ” But just how unlikely is it that a typical passenger will ever see that jungle of oxygen cups dropping from their panels to dangle overhead?
According to the Aviation Herald, loss of cabin pressure incidents occur an average of about three times a month. Considering that there are an average of 100,000 airline flights a day, the odds are a million to one against an incident on a given flight.