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If Oxygen Masks on Airlines Have Empty Bags, Where is the Oxygen Stored?

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If oxygen masks on airlines have empty bags, where is the oxygen stored?

C Stuart Hardwick:

Humans and airplanes both need oxygen, but high speed airliners operate much more efficiently at high altitudes where the air is thinner. The lack of oxygen doesn’t bother them because jet engines compress their intake air anyway, but above about 8000 feet, the lack of oxygen would start making passengers woozy, and at higher altitudes still, would be fatal.

That’s why airliners carry emergency oxygen. The cabin is normally pressurized to about 8000 feet, but if pressurization ever fails above about 14,000 feet, some passengers would be unable to absorb sufficient oxygen from the rarefied air and would grow faint, even ill—especially those who are old or infirm, and those accustomed to near-sea level pressure, which is a third of the global population.

We can tolerate much higher altitudes, though, if we have pure oxygen to breath instead of the 21 percent oxygen in ordinary air. Breathing supplemental oxygen, we can go up to about 35,000 feet (40,000 with a full face mask ensuring 100 percent undiluted oxygen). Much higher than that and we risk passing out or asphyxiation even with 100 percent oxygen. That’s why few airliners fly higher—passengers would need pressure suits or at least full face masks as backup life support. Were it not for that, planes would happily fly at 50,000, 60,000, or even 70,000 feet.

So ... to answer the question.

If you’ve ever gone scuba diving (or seen it on TV) you know that divers only get air when they draw a breath—their rig doesn’t just continually belch out air (unless the regulator is busted) because that would waste air.

That’s what the bag is for. The oxygen generator over your seat in an airliner does just continually belch out oxygen. There is no tank or regulator—just a canister containing chemical reactants which, once started, produce a continuous stream of oxygen until the reactants are used up (a few minutes, long enough to descend to thicker air).

The flimsy little bag is there to catch the stream of oxygen in between your breaths so it isn’t wasted. That’s it. It only inflates while you are exhaling, provided you are breathing slowly enough. That’s why it might not inflate (you might not give it a chance you panicky rascal).

This post originally appeared on Quora. Click here to view.

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Do 'Close Door' Buttons in Elevators Actually Do Anything?
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When you’re running late for work, one small comfort is finding an empty elevator waiting for you at your office building. You scurry inside, and since no one else is waiting to enter, you jab the 'close door' button. The doors comply, the elevator starts moving, and you breathe a sigh of relief.

This is a familiar scenario for many, but it’s also a big fat lie. That’s because most of the door-close buttons in U.S. elevators don’t actually work. In fact, they’re programmed that way.

But before you get ready to send off a strongly worded email to your office building’s elevator manufacturer, you may want to hear why this is the case. When the Americans With Disabilities Act was first passed in 1990, certain requirements for elevators were outlined, such as the installation of raised buttons, braille signs, and audible signals.

The act ensured that someone with a disability would have enough time to get inside, stipulating that elevator doors must remain fully open for at least three seconds and thereby preventing the button from cutting that time short. Some elevator manufacturers took it one step further by deactivating the button entirely.

Since the life span of an elevator is about 25 years and the Disabilities Act has been around for 28 years, it’s safe to assume that most of the elevators in operation today do not have a functioning 'close door' button, The New York Times reports. Only firefighters are able to close elevator doors manually through the use of a key.

It's important to note that there are exceptions to this rule, though. As the New York Daily News noted, New York City elevators are required by law to have working 'close door' buttons, even though some operate on a long delay (so long, in fact, that it calls the button's usefulness into question).

However, you’re in luck if you’re taking a lift (which, of course, is British for “elevator”). 'Close door' buttons are fully functional in most elevators in the UK, according to The Telegraph. A spokesman for the Lift and Escalator Industry Association told the newspaper that not all elevators have the button, but when they’re present, they do work. Again, the time it takes for the doors to shut after pressing the button varies from lift to lift.

While U.S. elevator manufacturers have a seemingly good reason for disabling the 'close door' button, some may question the point of propagating the myth and installing a button that serves no purpose in the first place. In response, some would argue that placebo buttons serve an important psychological function in society.

"Perceived control is very important," Harvard psychologist Ellen J. Langer told The New York Times. "It diminishes stress and promotes well-being."

That’s right: By believing that you’re in control of your fate—or at least how quickly you can make it up to the sixth floor—you’re better off. It doesn’t end with elevators, either. Buttons placed at city crosswalks are often disabled, and the thermostats in many office buildings are rigged so that the temperature can’t be altered (even if the numbers appear to change).

Some might swear up and down that elevator 'close door' buttons work, but this, too, could be your brain deceiving you. As author David McRaney wrote in an essay: “If you happen to find yourself pressing a nonfunctional close-door button, and later the doors close, you’ll probably never notice because a little spurt of happiness will cascade through your brain once you see what you believe is a response to your action. Your behavior was just reinforced. You will keep pressing the button in the future.”

According to The New Yorker, these buttons are designed to alleviate some of the subconscious anxiety that comes from stepping inside a tiny box that's hoisted up some 20 or 40 or 80 floors by a cable: “Elevator design is rooted in deception—to disguise not only the bare fact of the box hanging by ropes but also the tethering of tenants to a system over which they have no command."

So now you know: Next time you’re running late to work, take comfort in the fact that those few extra seconds you would’ve saved by pressing a functioning 'close door' button aren’t worth all that much in the long run.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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What’s the Difference Between Prison and Jail?
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Many people use the terms jail and prison interchangeably, and while both terms refer to areas where people are held, there's a substantial difference between the two methods of incarceration. Where a person who is accused of a crime is held, and for how long, is a factor in determining the difference between the two—and whether a person is held in a jail or a prison is largely determined by the severity of the crime they have committed.

A jail (or, for our British friends, a gaol) refers to a small, temporary holding facility—run by local governments and supervised by county sheriff departments—that is designed to detain recently arrested people who have committed a minor offense or misdemeanor. A person can also be held in jail for an extended period of time if the sentence for their offense is less than a year. There are currently 3163 local jail facilities in the United States.

A jail is different from the similarly temporary “lockup”—sort of like “pre-jail”—which is located in local police departments and holds offenders unable to post bail, people arrested for public drunkenness who are kept until they are sober, or, most importantly, offenders waiting to be processed into the jail system.

A prison, on the other hand, is usually a large state- or federal-run facility meant to house people convicted of a serious crime or felony, and whose sentences for those crimes surpass 365 days. A prison could also be called a “penitentiary,” among other names.

To be put in a state prison, a person must be convicted of breaking a state law. To be put in a federal prison, a person must be convicted of breaking federal law. Basic amenities in a prison are more extensive than in a jail because, obviously, an inmate is likely to spend more than a year of his or her life confined inside a prison. As of 2012, there were 4575 operating prisons in the U.S.—the most in the world. The country with the second highest number of operating prisons is Russia, which has just 1029 facilities.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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