Breathe easy in the clouds: aircraft pressurization 101

Flight crews will often tell you that the aircraft is pressurized for your comfort. While this is reassuring to hear, have you ever wondered what it actually means? What is cabin pressurization and why is it necessary?

While people can adapt to high altitudes, climbing and descending as quickly as an aircraft does would be extremely uncomfortable. The higher the altitude, the less oxygen there is in the air and the lower the overall air pressure is. If flights were not pressurized, passengers would be at risk of various physiological aliments. Because of this, federal regulations require that all commercial flights over 8,000 feet be pressurized.

So how does it work? Aircraft are pressurized by pumping cooled and humidified air into the aircraft’s cabin during flight. This flow of air into the cabin is constant. Depending on the aircraft, this air can be bleed air (air generated by the engines), fresh air from outside or a mixture of both. The pressurization system is designed to slowly raise and lower the cabin altitude as a flight climbs and descends, to allow as gentle a transition as possible for passengers.

When your flight is zipping along at 40,000 feet, the pressure in the cabin will be similar to the pressure at 5,000 or 6,000 feet in elevation. This is a comfortable elevation for the human body, but is still not the same as being on the ground. Essentially, being in a pressurized cabin is more like standing on a small mountain than being on the ground at sea level, or even at Asheville’s elevation of just over 2,000 feet. Most of the physiological quirks that some people experience when flying, like jet lag, are the result of the cabin altitude.

A depressurization event (when a pressurized aircraft loses cabin pressure for any reason) is extremely unlikely, but flight crews are trained extensively on how to handle them. In the event of a depressurization, oxygen masks will deploy for every passenger. Oxygen mask demonstrations are always a part of the flight attendant’s safety briefing, and if you’re a frequent flier, you could probably run the demonstration yourself after having seen it so many times. Oxygen masks are designed to deploy if the cabin altitude exceeds 14,000 feet for any reason. A little-known fact about oxygen masks is that there is typically an extra mask in every row of seats on a plane. This means an airplane with three seats on each side of the aisle will have eight masks in that row. These extra masks are for those traveling with a lap child (an infant in their lap), and is also why airlines have a restriction on the number of lap children that can be in any given row.

The number one priority in aviation is always safety, so you can be sure there are rules and regulations in place to govern safety around oxygen. For example, there must be enough oxygen on board to allow passengers to continue to breathe comfortably until the pilots can descend below 14,000 feet; there must be at least two hours’ worth of oxygen on board for each member of the flight crew; and all commercial aircraft must be able to descend from their cruising altitude to 10,000 feet in ten minutes.

While we’re on the subject, we may as well point out that the aircraft is pressurized from the cockpit to where the tail starts to narrow, and that includes the cargo area of the aircraft, so no need to worry about your furry friends traveling in cargo below – they’re enjoying the comfort of the pressurized aircraft, too!