horizonsgirl

Someone told me that extra oxygen is pumped into airplanes to relax the passengers. This doesn't make a lot of sense to me. Any comments?

J62

Airplane cabins are pressurized, so of course there is more oxygen available compared to outside. This is absolutely necessary due to the altitude planes fly - over 30,000 ft.

So technically, yes oxygen is pumped into airplanes, along with a lot of nitrogen. As for extra oxygen, then only supply on board is the emergency supply, which isn't designed to last for a long time - just long enough until a plane can descend to a safe altitude - somewhere below 10,000 feet or so.

Cabin air is continually refreshed with outside air so it would be cost, weight, and perhaps safety (high pressure canisters) prohibitive to carry large amounts of oxygen to pump extra oxygen into the plane.

horizonsgirl

Thanks J62. The friend who told me this made is sound like more O2 than normal in order to relax people.

After I posted my question I read post 19 and got good info as well.

Thanks for your immediate reply!

rkkwan

Cabins in modern jet airliners are pressurized. It is equivalent to air pressure of about 7,000ft above sea level. But the components are the same as outside air - about 80% nitrogen, 20% oxygen and the rest carbon dioxide - no extra oxygen supplied.

The much delayed Boeing 787 (and probably also the upcoming Airbus 350) will allow higher air pressure because of its composite fuselage. So, cabin air pressure will be equivalent to 5,000ft to 6,000ft above sea level. Passengers will feel more comfortable in those aircraft than current ones.

NoFlyZone

Actually, at cruise altitude in a pressurized aircraft there is on the order of 25% less oxygen than at sea level. About the same as at 7000 to 8000 feet. More O2 in a 787 as noted above.

AnthonyGA

What you were told is a highly distorted version of reality.

Commercial airliners fly at very high altitudes. At these altitudes, the air is very thin ... too thin to breathe easily without extra oxygen. If the air pressure inside the cabin were the same as outside, everyone would have to wear an oxygen mask for the entire flight. To make this unnecessary, the cabin is pressurized, with air pumped in to raise the cabin pressure until it is very close to what it would be on the ground. With the cabin pressurized, passengers can remain comfortable and don't have to wear oxygen masks, since the higher-pressure air contains more than enough oxygen to allow normal breathing.

Thus, extra oxygen isn't pumped into the cabin, but plain air is. The higher pressure that results also provides more oxygen, which in turn keeps passengers comfortable. It doesn't necessarily relax them, although it's surely more relaxing than having a mask strapped on for a 3-hour flight.

The cabin pressure is equivalent to the air pressure on a mountain, roughly. It depends on how high the airplane is flying. Usually the "cabin altitude" is between 5000 and 8000 feet, which is comparable to the altitude of Denver or Telluride, Colorado, respectively. The maximum (by law) is 8000 feet, which is similar to driving up into the mountains to ski, but is still low enough to not present any difficulties for breathing.

In small private planes that are not pressurized, the cabin pressure is the same as the air outside. For this reason, if you're riding in a small Cessna or Piper aircraft, the law requires that you wear an oxygen mask if the airplane goes above 15,000 feet (about as high as the highest mountains in Colorado). The pilot has to wear an oxygen mask above 12,500 feet. There isn't any actual danger to passengers, though, at the altitudes attainable by these small aircraft, apart from the fact that they might pass out temporarily without oxygen or develop other symptoms.

Airliners fly a lot higher. At 36,000 feet, oxygen is mandatory, even for brief exposures to that altitude. That's why oxygen masks immediately drop in front of passengers if there's a loss of pressure in the cabin.