The Bag of Air That Protects Us During A Collision in Automobile
Due to civilisation and modern day living conditions, it is now a norm for people to use one form of transport or another to get to another destination.
The three mode of transport is sea, land, and air transport. Out of that, the passenger transport via automobile comes first at 16,000 billion passenger-km, with the least being rail at 250.
The World Health Organisation puts the global number of road traffic deaths in the year 2013 at 1.25 million. This statistic is a staggering 3,400 deaths daily.
The motor vehicle accident is a leading cause of deaths in young adults aged between 15-29 and is rated the 9th cause of death for all ages globally.
The number could have been worse without the use of seatbelts and airbags.
Airbag
An airbag is a flexible inflatable fabric cushion installed in vehicles which by design rapidly fills with air during an impact when triggered by a sensor.
Ever since the invention of airbags, the mortality rate by vehicle accident had dropped to 24% worldwide, and 63% in the USA within the year 1992 to 1997 according to this report.
A little history
Until 1951, vehicles do not have airbags installed in them. But an American inventor and engineering technician, John Hedrick, patented one in 1951 which he named a "safety cushion assembly for automotive vehicles."
But the only interested car companies were General Motors (GM) and Ford. The GM car manufacturers later went on to be the first to deploy airbags, commercially, in their Oldsmobile and Buick automobiles from 1975 to 1976.
But other car companies were dragging their feet. It was in 1998 that it was made mandatory for all vehicle to have airbags installed.
Why airbags?
We will have to revisit one of the laws of physics made in the 17th century by Isaac Newton and published in 1687. The Newton's laws of motion are three, but for the post, we are only interested in the first law of motion which is sometimes known by the name of Law of Inertia.
Inertia is simply the tendency of a body to resist a change of motion but rather to continue in the direction of motion.
The first law was pretty straightforward; it states a body in motion will continue in motion, while an object that is at rest will remain at rest unless an external force acts on it.
We obey this law in our daily lives. The side body movement we experience when a car takes a corner or negotiates a sharp turn a little too fast.
The feeling of being "sucked" back into the car seat when an automobile does a rapid acceleration. The inertia makes the body to continue at rest, but the forward motion of the acceleration counters that.
Even while relaxing at home and the public power supply suddenly goes off, something very familiar here in my country, you will notice the electric fan continue rotating until it gradually comes to a halt.
The airbags keep the passenger safe from home as it inflates and cushions the forward thrust when an automobile was suddenly forcefully brought to a halt by an impact/collision.
How it works
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[Image Showing Airbag Dummy Test from Diamler Chrysler AG via Wikipedia Commons: 1,2, and 3
But due to momentum from motion, a sudden stop, even when the seatbelt keeps you strapped in, will force the head, which weighs a surprising 3-6kg to hurtle forward (see the image of the dummy). The airbag once inflated, prevents the head from smashing into the steering.
The reaction of the air that inflates the airbag is super fast. It is between 20 millisecond and 40 milliseconds. How do we get such rapid inflation in such a very short time?
This air is not from a compressed gas source instead it is from a chemical reaction. I know the automobile may be the last place to think of chemistry, but there you have chemistry to the rescue.
In the early days of the airbag technology, inflating the bag involve the use of compressed air stored in a tank. That was the practice until 1968 when John Pietz, a chemist pioneered the use of solid-state sodium nitride (NaN3).
When it comes to the airbag technology, timing is everything. If it deploys too slow, the driver and passenger safety is at risk.
Here, the crash sensor plays a critical part. The sensor is a steel ball that slides inside a smooth bore housing. Usually, the ball is held by a permananet magnet or a spring which secures the ball in place as the vehicle navigates over potholes or uneven roads.
But when the car suddenly decelerates as a result of a collision or impact, the ball goes free and slides along the bore to activate an electric circuit which initiates the airbag's inflation. All this as I mentioned before happens in the milliseconds (not more than 40ms) time range.
The inflation is not a result of compressed air but rather as a result of a chemical reaction which generates gas inside the airbag.
The airbag has three chemical components whicch are silica (SiO2), Sodium azide (NaN3), and pottasium nitrate (KNO3).
Reaction One: 2NaN3 → 2Na + 3N2
About 130mg of sodium nitride (2NaN3) can produce up to 67 litres of nitrogen gas needed to inflate a standard airbag.
The sodium azide (2NaN3) decomposes under heat to produce sodium (2Na) and nitrogen gas (3N2).
Of the two chemical products, sodium an alkali metal, can cause severe burns to skin or eye contact.
To prevent that from happening:
Reaction Two: 10Na + 2KNO3 → K2O + 5Na2O + N2
The sodium is made to react with potassium nitrate (2KNO3) and the products are potassium oxide (K2O , sodium oxide (5Na2O), and nitrogen (N2), which produces more nitrogen as well.
The potassium oxide is harmful too so a further third reaction gives:
Reaction Three: K2O + Na2O + SiO2 → Na2K2SiO4
The final reaction produces a harmless white powdery substance known as alkaline silicate glass (Na2K2SiO4).
Conclusion
There has been attempt pioneered by Honda with research on the subject from 1990. The airbag is to lessen the severity of the rider forward throw from the motorcycle in the event of a collision.
You can visualise the effect of the collision when riding on a motorcycle by taking a look at this gif. Since most injuries and deaths are mostly from the riders getting either thrown under a vehicle or onto incoming traffic, this measure appears useful.
The National Safety Council has an estimated 1040 lives saved in the USA in 1998 as a result of airbag use. The same year also, 100 children lost their lives as a result of improper fastening of seat belts and placing children in front seats.
![By High Contrast [CC BY 3.0 de], from Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Motorradairbag.JPG){kind=link}
![By Goldom [CC BY-SA 3.0], via Wikimedia Commons](https://en.wikipedia.org/wiki/File:Air_bag_warning_sign.jpg){kind=link}
The right sitting position and use of seat belts, which apart from restraining us also places one in the right spot for the best possible protection in the event of a crash. I survived this accident because I was wearing a seatbelt.
REFERENCES
- Epidemiology of motor vehicle collisions
- List of countries by traffic-related death rate
- Mode of Transport
- Airbags
- Encylopedia:Airbags
- Scientific American: How Airbags Work
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Without airbags as a cushion, the body created by the seatbelt to remove damage to the neck and chest.
Airbags create views and enhance for current queries. You need to know, the material used for airbags is nylon with small holes. From this hole, the gas that causes the airbag to expand will come out and the airbag will widen.
Airbags expands due to the gas Nitrogen is blown into the air bags of the fabric that we have breathed 78% of Nitrogen gas. So, the gas is safe to breathe.
When you see a cloud quickly fill the car, do not panic first. The actual smoke cloud is corn flour or talcum powder used to prevent sticky airbag still in folded condition. Very dangerous when sticky airbags add to the accident.
That was an insightful comment. Thank you so much.
Your explanation of the working mechanism of airbags is succinct and very detailed enough for a typical layman to understand.
I just read about your miraculous survival of a fatal accident, thanks to seatbelt. So sorry I didn't read the story back then which was why I didn't comment to rejoice with you for surviving the ugly event.
Do have a happy Sunday.
@eurogee of @euronation community
Thank you. We only try :)
I love how you made this post simple and easy to understand and also interesting...
I've always heard about airbags but actually never taken time to learn how they work but this post as well as @jamalgayoni's comments were really helpful...
While growing up, I always thought airbags were magical coverings that just happen to pop up whenever accidents occur... lol... although, I never quite saw them pop up or anything but I once overheard my parents talking about it and I've always noticed it inscribed on the dashboards of a few cars.. honestly, I hope I never see one cos I'm not interested in being involved in an accident of any sort..
By the way, I'm sorry to hear about your accident and I'm glad you were saved by the seatbelt.. Its a reminder that it's always important to follow all safety precautions when in a moving vehicle. You're a living proof of that.
But well done, sir!
This post was insightful
I'm all good now, thank you looking out. Yeah, it pains me to see kids in front of vehicles (without seat belts) or even riding on their parent's laps! The technology of airbag is simple but mostly not something many know.
True... many people don't know better and some actually know better but don't even care about their (or their children's) safety...
You're doing your little part to spread awareness and that really matters, sir..
Wow! This is quite a brilliant explanation of the concept, theory and science behind the airbags. No doubt it has been a great tech and science revolution in the automobile industry. Never really paid much attention to the science behind it. Thanks for sharing @greenrun
I've always been a fan of it after surviving two accidents.
Wow! Two accidents? Sorry about that bro. I'm glad you live to tell tale.
Me too :)
The safety of the passengers is one which automotive engineers take as paramount. Various safety devices have been incorporated into the automobile like the airbag which you have discussed.
Permit me to add that the immediate partial deflation of the airbag is also important as this is important for the safety of the driver. A cushion effect is needed otherwise, it will be like hitting the head on a rock. To provide this, the airbag must be partially deflated by venting some of the Nitrogen.
By doing so the bag becomes softer and provides some cushion.
I salute your writing sir. Happy sunday.
Yeah, if not partially deflated it may crush or choke the person it was suppose to protect.
That's good engineering - every situation has been considered.
Just like those three reactions. When one leads to a harmful product, a means have been devised to neutralize it until it is safe.
A good engineering practice or invention is one that has some safety incorporated in it.
I couldn't agree more.
Thanks for the insighful post - never knew about the chemical reaction involved here and I used to always wonder how an air was pumped into an airbag using a compressor quickly enough to cushion the driver.... now I know better!
I'm glad you find the post useful.
Oga green, educative as usual. Sometimes I wish I could be as good as you are in issues such as this. I doff my hat for you.
Someone sent you a message on my show, let's talk about it with @oluwatobiloba. So you could check my blog to view the message.
Ok. I'd definitely check your blog to see the message. Thank you for the kind compliments.
This is detailed.. I was actually thinking compressed air were the brains behind the airbag i never knew chemistry was very much involved.
One should not play with these stuffs in vehicles i am almost sure many cars have their airbags damaged. Especially those who visit the road side mechanic.
Thanks for the education. I look forward to reading more of your posts.
If airbag is faulty, it shows in one of those indicators in the dashboard. Unless the sensors are damaged too.
Yeah.. Roadside mechanics are never bothered about the dashboard lights.. They mostly say its faulty.
one of the very important safety devices that are incorporated in the automobile is the airbag.
Although there has been introduction of pre-collision technology in automobiles, there is still relevance for the airbags.
One should not drive a car that has its air bags removed because you never can tell. Even when buying a second hand car, one should be sure of a functioning airbag system.
nice post sir
Collision detection mechanism? There are those and it works in some circumstances. That's awesome, but not when a vehicle loses control and heads to that tree or that street utility pole.
yes thats why i said the air bags still find relevance!
Yes, that's right.
Air bags are indispensable and they are life saver.
It has saved a very good friend of mine when he had an accident. An accident that would have been fatal., but because of air bag, he didn't loose his life.
But i have a question,
Initialy it was mystery to me how these bags bumped out during accidents, but with this article I have been able to understand the mechanics behind it. I guess a mystery has been unraveled.
Thanks @greenrun
Thank you too for taking out time to check on my blog.