8 secret airplane safety features you didn't know existed

• Planes are designed with many safety features - from flame-resistant seat cushions to hidden bathroom locks.
• Other safety features include black triangles and yellow hooks.
• Airplanes also don't have oxygen tanks, but they have ashtrays.
• This video reveals 8 secret safety features you probably didn't know existed.
• Visit Business Insider's homepage for more stories.

Following is a transcript of the video.

Narrator: This is the bathroom door on an airplane and it can save your life. Not because it's the only thing standing between you and the guy that ate an airport burrito before he got on board. It actually has a hidden safety feature. Can you figure it out?

1. Yellow hooks

In case of an emergency that requires the pilot to land on the water, you'll be grateful for these little yellow hooks. The number and placement of hooks on each wing vary from plane to plane, but they all do the same thing: help passengers to safety. They're an anchor for ropes, which passengers use to steady and pull themselves across the wing especially during a water landing. The ropes and hooks can also be used to tether rafts to the plane so they don't float away as passengers board.

2. No oxygen tanks

Let's say your plane does depressurize. You know the drill - pull down on the mask to extend the tube, cover your nose and mouth with the yellow cup, and always put your own mask on first. But wait, why do you have to pull down on the mask? It's not to reach your face. It's actually to start a chemical reaction. T

here are no oxygen tanks on airplanes. They're just too heavy and bulky to be practical. Instead, the panel above your head contains a chemical oxygen generator. It's a small canister that holds sodium chlorate, barium peroxide, and a pinch of potassium perchlorate. And when all three mix together, the extremely hot chemical reaction lets off oxygen.

3. Fire-resistant cushion

Your seat cushion functions as a flotation device, but did you know it's also fireproof? Let's take this back a few decades. During a 1967 test for the first Apollo moon mission, three astronauts were killed when the interior of the capsule caught on fire. An investigation showed that the craft was filled with highly flammable materials including the foam in the seat cushions.

This led NASA to conduct a whole slew of research for a way to cover flammable things with a fire-resistant material. So in 1984, the Federal Aviation Administration issued new regulations regarding the flammability of airplane seats. And in fact, it's estimated that 20 to 25 lives are saved each year because their seats don't catch on fire.

4. Black triangle

Above some of those flame-resistant seats, you might see a little black or red triangle. Those triangles actually signify what's nicknamed "William Shatner's seat." It's a reference to a 1963 episode of "The Twilight Zone," in which Shatner's character sees a gremlin on the wing of the plane. The triangles signal to the crew which windows have the best view of the wings in case a flap malfunctions or to check to see if they've been deiced.

5. Little window hole

While you're staring at the gremlin on the wing, you might notice a small hole in the window. Usually not a good feature for a window, but necessary in this case. It's called a bleed hole. And it prevents your airplane window from blowing out. That's because the air pressure inside the plane is so much greater than outside, which would cause any normal window to explode.

But the windows on an airplane are made up of three panes: inner, middle, and outer. The outer pane takes the pressure, the middle acts as a fail-safe, and the inner is just there so passengers don't mess with the other two. The hole also lets moisture escape from the gaps so the windows don't fog up or freeze.

6. Dimming lights

If the idea of your window popping out mid-flight causes you stress, just try to keep the shade up anyways. That simple action could give you peace of mind and potentially save your life. Before taking off and landing at night, crews will often dim the cabin lights and ask passengers to open their shades. This is to give their eyes time to adjust to the darkness. In case of evacuation, passengers' eyes will already be acclimated to the blackness outside. If the lights stayed on, their eyes would need time to adjust and they'd end up wasting precious seconds stumbling blindly instead of quickly evacuating.

7. Hidden bathroom lock

While joining the mile-high club might seem like a fun idea, you won't get the kind of privacy you might expect. In fact, a crew member could open the bathroom door at any moment no matter if you locked it or not. On the outside of most airplane bathroom doors is a little plate that says "LAVATORY." And under that little plate is a latch that unlocks the door from the outside. This allows the crew to access the bathroom in case of an emergency.

8. Ashtray

While you're in the bathroom, you might notice an ashtray. "But wait," you think to yourself, "I thought it was illegal to smoke on planes!" You're right! Smoking on an airplane has been banned on US airlines since the late 1980s and could saddle you with a fine of up to $25,000. Even with the threat of a fine, the Federal Aviation Administration isn't taking chances. It lists ashtrays in bathrooms as legally required to meet the minimum equipment needed for a plane. Trash cans on a plane are mostly filled with flammable materials, like cocktail napkins. So tossing a cigarette butt into one of those would not be good.

After all, there are still plenty of things in a plane that aren't covered in flame-resistant material.