SEMI REPORT ON AIRBAG SYS

AIRBAG SYSTEMS

SEMINAR REPORT

SUBMITTED BY

REGEIF MOHAMMED ALI(AXALEME040)

In partial fulfilment for the award of the degree

Of

BACHELOR OF TECHNOLOGY

IN

MECHANICAL ENGINEERING

AXIS COLLEGE OF ENGINEERING AND TECHNOLOGY, AMBANOLY

UNIVERSITY OF CALICUT, KERALA

2015

DEPARTMENT OF MECHANICAL ENGINEERING

CERTIFICATE

This is to certify that this project report titled

AIRBAG SYSTEMS

Was prepared and presented by

REGEIF MOHAMMED ALI (AXALEME040)

of the eighth Semester Mechanical Engineering

in partial fulfilment of requirement for the award of

Degree of Bachelor of Technology in Mechanical Engineering under the University of

Calicut during the year 2011-2015

Asst Prof .ABILASH .K.J Prof .P.S. SIVARAMAN

Seminar Guide H.O.D

Dept .of . Mechanical Engg

iii

ACKNOWLEDGEMENT

No achievements can be made by individuals alone .it would be incorrect if i don't

thank the people who an important role in finishing the seminar report. First and foremost i

would like to thank god almighty for blessing me with his grace and taking my endeavour to

a successful culmination. I would like to show gratitude to esteemed principal Prof. Dr.

Anslam Raj who helped me in every possible ways. I would like to show gratitude to my

Head Of the Department Of mechanical Engineering Prof P.S Sivaraman, who helped me in

every possible ways. I express my heartfelt thanks to our internal guide & inspiration Asst.

Prof Abhilash .K J, for his valuable support, guidance & constructive ideas throughout the

seminar.I thank all the lecturer & non-supporting staff for their help & I would like to thank

my friends who helped me for the successful completion

iii

ABSTRACT

The present paper represents a brief review of life saving system in rollover accidents, while

driving on the road by a four wheeler. An Airbag is an automotive safety restraint system for an

occupant as well as passengers. The system consists of a flexible fabric envelope or cushion, designed

to inflate rapidly during an automobile collision. Its purpose is to cushion occupants during a crash and

provide protection to their bodies when they strike interior objects such as the steering wheel or a

window etc. Thus it lowers the number of injuries by reducing the force exerted by steering wheel,

windows and the dashboard at any point on the body. Continuing research and developments are going

on in its module design, combustible material, air bag fabric design and material, coating etc. in

making this life saving safety device further efficient. However, success of any safety restraint device

depends on its correct implementation and certain safety rules to be followed

iii

LIST OF CONTENTS

CHAPTERS TITLE PAGENO.

ACKNOWLEDGEMENT iii

ABSTRACT iv

LIST OF CONTENTS v

LIST OF TABLES vii

LIST OF FIGURES viii

LIST OF ABBREVIATIONS x

1 INTRODUCTION 1

2 LITERATURE REVIEW 2

2.1 OVER VIEW 2

2.2 HISTORY 2

2.3 CHEMISTRY OF AIRBAG 5

3 MAIN PARTS 7

3.1 AIRBAG MODULE 7

3.1.1 AIR BAG PRODUCTION PROCESS 8

3.1.2 RAW MATERIALS USED IN AIR BAG 8

3.2 SENSORS 10

3.2.1 MASS TYPE SENSOR 10

3.2.2 ROLLER-TYPE SENSOR 11

3.3 AIRBAG CONTROL UNIT 12

4 WORKING 15

5 AIRBAG TYPES 16

5.1 FRONTAL AIR BAGS 16

5.2 HEAD PROTECTION BAGS 17

5.2.1 SIDE CURTAIN AIRBAGS 18

5.3 SIDE IMPACT AIR BAGS 19

5.4 OCCUPANT POSITIONING AIR BAGS 20

5.4.1 KNEE BAGS OR BOLSTERS 21

5.5 CARPET BAGS 21

5.6 ANTI-SLIDE SEAT BAGS 22

5.7 MISCELLANEOUS AIRBAGS 23

iii

6 AIRBAG RISKS 26

7 CONCLUSION 27

8 REFERANCE 28

iii

LIST OF TABLES

TABLE NO: TITLE PAGE NO:

2.1 Showing the same statics for belted, non-belted and overall 4

2.2 Showing chemical reactions inside and airbag 6

3.1 properties of these commercially used fabrics 8

iii

LIST OF FIGURES

FIGURE NO: TITLE PAGE NO:

1.1 Driver and front passenger air bag 1

2.1 Statistics for Airbag Application in Vehicles 4

2.2 Airbag Unit growth in Vehicles, by Region- 2000 to

20005

5

2.3 Chemicals inside the airbags 5

3.1 ON/OFF switch of air bag system 7

3.2 Air bag fabric productions flow-chart 8

3.3 Mass type sensor 11

3.4 Roller-type sensor 11

3.5 Airbag control unit 12

5.1 Driver side airbag 16

5.2 Shows the deployed first stage of a air bag 17

5.3 Head protection airbags 18

5.4 Side curtain airbags 19

5.5 Side impact airbags 19

5.6

Left shows an identification stamp. On the right is a

picture of a deployed knee bag.

21

5.7 Picture of a deployed carpet bag 22

5.8 Anti-slide Seat bags 22

5.9 Air bag in the head rest of the rear seat in a passenger car. 23

5.10 Air bag installed in the seat belt. 23

5.11 Pedestrians protection airbags 23

5.12 This air bag to deflect the path of the rider up and

over the impacted vehicle

24

5.13 Airbag vest is available to motorcycle riders 24

SEMINAR REPORT 2015 AIRBAG SYSTEMS

Dept. of Mechanical Engg. 9 AXIS CET

LIST OF ABBREVIATIONS

1. DOT - Department Of Transportation

2. SRS - Supplemental Restraint System

3. US - United States

4. NaN3 - Sodium Aside

5. Na - Sodium

6. N2 - Nitrogen gas

7. KNO3 - Potassium nitrate

8. K2O - Potassium oxide

9. SiO2 - Silicon dioxide

10. Na2K2SiO4 - Alkaline silicate glass

11. UV - Ultraviolet

12. ECU - Electronic Control Unit

13. FMVSS - Federal Motor Vehicle Safety Std

14. ITS - Inflatable Tubular Systems

15. HPS - Head Protection Systems

16. NHTSA - National Highway Safety Admin



CHAPTER 1

INTRODUCTION

Fig no: 1.1 Driver and front passenger air bag

For many years, the trusty seat belt provided the sole form of passive restraint in our cars. Seat

belts have been proven to be effective in saving lives and preventing or lessening injuries in

automobile accidents.. The first passive restraints were modifications of seat belts themselves; the belts

were coordinated with operations of opening the car doors and starting the automobile, which caused

belts built into tracks in the doors to wrap around the driver or passenger when the seat was occupied.

Concurrently, the airbag was devised as a secondary form of passive restraint during impact.

Air Bags have been under development for many years. They were initially used and designed

to be used in fighter planes during world war second. In the 1980’s the first commercial air bags

appeared in automobiles. Since 1988, all new cars have been required to have air bags on both driver

and passenger sides. To date, Statistics show that air bags reduce the risk of dying in a direct frontal

crash by 30 percent. Other than steering Wheel mounted or Dash board mounted bags, there are seat-

mounted and door mounted side air-bags. Air bags were invented as the result of serious government

discussions and industry research and tests.



CHAPTER 2

LITERATURE REVIEW

2.1 OVERVIEW

Airbags are considered as passive device because no action by the vehicle occupant is required

to activate or use the airbag This is in contrast to seat belts, which are considered active devices

because the vehicle occupant must act to enable them. Note that this is not related to active and passive

safety, which are, respectively, systems designed to prevent accidents in the first place and systems

designed to minimize accidents once they occur. For example, the car's Anti-lock Braking System will

qualify as an active-safety device while both its seatbelts and airbags will qualify as passive-safety,

which are, respectively, systems designed to prevent accidents in the first place and systems designed

to minimize accidents once they occur. For example, the car's Anti-lock Braking System will qualify

as an active-safety device while both its seatbelts and airbags will qualify as passive-safety devices.

Further terminological confusion can arise from the fact that passive devices and systems those

requiring no input or action by the vehicle occupant can themselves operate in an active manner; an

airbag is one such device. Vehicle safety professionals are generally careful in their use of language to

avoid this sort of confusion, though advertising principles sometimes prevent such syntactic caution in

the consumer marketing of safety features. Various manufacturers have over time used different terms

for airbags. General Motors' first bags, in the 1970s, were marketed as the Air Cushion Restraint

System. Common terms in North America include Supplemental Restraint System and Supplemental

Inflatable Restraint, these terms reflect the airbag system's nominal role as a supplement to active

restraints, i.e., seat belts.

2.2 HISTORY

The first concepts for an automatically inflating air cushion used as an impact protection for car

passengers were discussed in the sixties, approximately 10 years after corresponding patents had been

granted . John HETRICK'S patent describes a general airbag system in which a self-opening airbag is

automatically inflated following a sudden deceleration of the vehicle. In the USA ordinances FMVSS

208 was passed in the middle of the sixties against the background of increasing numbers of accidents,

to improve vehicle safety, thereby it called Safety Act. A bundle of new ordinances were planned to

improve safety in traffic. It was not until 1984, following long and controversial discussions, that an

agreement could be reached on the introduction of a passive restraint system on September 1, 1989 for



all new vehicles registered in the USA. These automatic restraint systems could be automatically

closing seat belts or the airbag. In order to be able to comply with the new ordinances (FMVSS 208)

immediately after they come into force, airbag developments were also initiated and intensified by

European automobile manufacturers; primarily by Mercedes-Benz. The basic development of passive

restraint systems stepped up at Mercedes-Benz from 1967 onwards. This first development stage from

1967 to 1972 is referred to as the principle functional proof. However, General Motors has also

introduced its first airbags in the early 1970s but consumer did not readily accept them. The market for

airbag was assured by US when the Department of Transportation (DOT) implemented the Federal

Motor Vehicle Safety Standards (FMVSS) 208inch 1984 as mention above. Because of this law, the

US leads the commercialization of airbag. The airbags of initial phase were inflated using compressed-

gas canisters. However, the pressure canisters could only be accommodated in the instrument panel.

Connection to the steering wheel proved problematic since it could only be sealed with great

difficultly. In the next development phase experiments were carried out with liquefied gas and solid

fuels. The solid propellant should supply the thermal energy needed to expand the liquid Fringe. . The

airbags of initial phase were inflated using compressed-gas canisters. Although the necessary inflation

time of 1/30 second was reached this system was still too heavy. A neoprene-coated polyamide fabric

was initially determined as a suitable material for the airbag.

After 1970, research concentrated on an inflator filled with solid fuel to inflate the airbag.

Together with development partners from the chemicals and automotive industries, this method of

producing the gas was perfected for series production as of 1974. In December 1980, the first vehicle

with a driver airbag was launched by Mercedes Benz. Seat belt tensioner were also offered for the

driver and front seat passenger. As of 1988 front-seat passengers were also protected by an airbag.

Since the beginning of the nineties, all automobile manufacturers have been offering airbags as a

standard feature or optional extra, even in compact class cars. . The airbags of initial phase were

inflated using compressed-gas canisters. However, the world-wide use of the airbag system didn't

proceed harmoniously since on the US-American market it is specified as the only restraint system

(passive system) whereas in Europe it has been developed as an additional safety device (SRS:

Supplemental Restraint System) to the seat belt system. . The airbags of initial phase were inflated

using compressed-gas canisters. These different developments have affected the size of the airbag and

inflator. As a sole passenger protection system the airbags must be much bigger and must inflate

earlier since the unprotected passenger collides faster with the instrument panel. The number of

persons, driver and passenger killed in traffic has dropped continuously since 1970.



Table no: 2.1 Showing the same statistics for belted, non-belted and over all

As a result of which in fig no:2.1 air bag penetration in the market has also get hiked from 1999 to

2005 . Airbag growth has also increased accordingly in every region of the vehicle with the stringent

demand of the safety

Fig no: 2.1 Statistics for Airbag Application in Vehicles

.Thus development of Federal rules, increased public awareness for safety and concern for safety has

enhanced the growth of air bags in the market as shown in fig no:2.2



Fig no: 2.2 Airbag Unit growth in Vehicles, by Region- 2000 to 20005.

2.3 CHEMISTRY OF AIRBAGS

Inside the airbag in fig no:2.3 is a gas generator containing a mixture of NaN3, KNO3, and

SiO2. When the car undergoes a head-on collision, a series of three chemical reactions inside the gas

generator produce gas (N2) to fill the airbag and convert NaN3, which is highly toxic, to harmless

glass. Sodium azide (NaN3) can decompose at 300oC to produce sodium metal (Na) and nitrogen gas

(N2). The signal from the deceleration sensor ignites the gas-generator mixture by an electrical

impulse, creating the high-temperature condition necessary for NaN3 to decompose. The nitrogen gas

that is generated then fills the airbag. The purpose of the

Fig no: 2.3 Chemicals inside the airbags



KNO3 and SiO2 is to remove the sodium metal (which is highly reactive and potentially explosive, by

converting it to a harmless material. First, the sodium reacts with potassium nitrate (KNO3) to produce

potassium oxide (K2O), sodium oxide (Na2O), and additional N2 gas. The N2 generated in this second

reaction also fills the airbag, and the metal oxides react with silicon dioxide (SiO2) in a final reaction

to produce silicate glass, which is harmless and stable. (First-period metal oxides, such as Na2O and

K2O, are highly reactive, so it would be unsafe to allow them to be the end product of the airbag

detonation.)

Table no: 2.2 Showing chemical reactions inside an airbag

Reaction 1

2NaN3 2Na + 3N2

Reaction 2

10Na + 2KNO3 K2O + 5Na2O + N2

Reaction 3

K2O + Na2O + SiO2 Na2K2SiO4 (alkaline silicate glass)



CHAPTER 3

MAIN PARTS

The air bag system consists of three basic parts- an air bag module, crash sensor and a diagnosis unit.

Some systems have ON/OFF switch to deactivate air bag system.

Fig no: 3.1 ON/OFF switch of air bag system

3.1 AIRBAG MODULE

The air bag module fig no:3.1 contains both an inflator unit and the lightweight fabric air bag.

The driver air bag module is located in the steering wheel hub, and the passenger air bag module is

located in the instrument panel. When fully inflated, the driver air bag is approximately the diameter of

a large beach ball. The passenger air bag can be two or three times larger since the distance between

the right-front passenger and the instrumental panel is much larger than the distance between the driver

and steering wheel



3.1.1 Air bag production process

Typical manufacturing line for air bag has been shown fig no:3.2. Airbags can be manufactured

by either of the mechanisms of fabric manufacturing, weaving and non- woven fabric manufacturing

process

Fig no: 3.2 Air bag fabric productions flow-chart

3.1.2 Raw materials used in air bag

Mostly used raw material as shown in table no:3.1 for the airbag fabric is nylon 6, 6 yarns in

the deniers ranging from 420 to 840. The side impact airbags used 1880 D nylon- 6.6 .

Table no: 3.1 Properties of these commercially used fabrics



Table shows the important properties of these commercially used fabrics. They are generally woven,

with the construction of either 840 X 840 D, 98 X 98 /dm plain weave, 60 width or 420 X 420 D, 193

X 193 /dm plain weave, 60 width Usually Rapier with insertion rate of 400 m/min has been found

most suitable for weaving airbags. Since, it can maintain warp tension with accuracy of 1 can per war-

p12-14. Even water jet and air jet with insertion rate of 600 m/min are being used15. Commonly, the

airbag made were coated by neoprene, but recently silicon coated and uncoated varieties have become

popular. Coated airbag are generally preferred for driver seats. The weight per unit length uncoated

one is higher than coated bags, i.e. 244 - 257 Vs 175 g/m2. Today, the latest research on potential

airbag materials includes High tenacity polyester, Nylon 4, 6, etc. apart from Nylon 6, 6. However

Nylon 6, 6 has the most superior quality in all. Air bag fabric has to keep a balance between two

extreme conditions . It has to be sufficiently flexible to fold into relatively small volumes. At the same

time it should be sufficiently strong to withstand the deployment at high speed, e.g. under the influence

of an explosive charge, and the impact of passengers or other influences when inflated. To play this

role successfully airbag fabric should possess following quality parameters:

Small fabric thickness.

Low specific fabric weight.

High tenacity in warp and weft direction as well as toughness.

High tenacity for furthers tearing

High elongation.

Good resistance to aging.

Heat resistance up to 190 0C.

Good resistance to UV light.

Low and very even air permeability.

Reduced cost.

Precisely controlled gas permeability.

Excellent seam integrity.

Improved pliability and pack height

Reduced value or burn through resistance.

3.2 SENSORS

The crash sensors are located either in the front of the vehicle and/or in the passenger compartment.

Vehicle can have one or more crash sensors. The sensors are activated by forces generated in significant



frontal or near-frontal crashes only and not during sudden braking or while driving on rough or uneven

pavement. By function, there are 2 types. Impact sensors and Safing sensors. The forward sensors are located

in various locations forward of the passenger compartment. Some are located inside the fenders, some

are on the cowl, some are attached to the core support in front of the radiator. Rear sensors are also

known as safing sensors as their function is to determine that a crash has occurred. Rear safing sensors

are located in various locations in the passenger compartment depending on the manufacturer. Some

are integrated with the Control/Diagnostic Module. The rear safing sensor must close before the

forward sensors to avoid airbag deployment in cases where the impact is not severe enough to cause

deployment. When the vehicle is parked with the ignition off deployment is very unlikely because

there is no power to the circuits for deployment. Airbag impact sensors, sometimes colloquially called

crash sensors, are important safety features for your vehicle. These sensors, located throughout your

vehicle, detect a collision and trigger the airbags to go off. They are usually found at the front of the

vehicle, behind the front fender, to detect a frontal impact, and in the side columns to detect a side

impact. The exact number and location of airbag sensors you have will vary from one model to

another, but those are the most frequently used locations.

3.2.1 Mass type sensor

An impact sensor in fig no:3.3 is normally fitted to the front of the vehicle as this is where a

collision is likely to occur. The sensor is positioned inside the engine and a similar safety sensor is

located inside the passenger zone to the vehicle. This safety sensor is required to measure the intensity

of the collision to determine whether the impact is over a certain threshold to justify release of an

airbag. Both types of sensors (termed inertia sensors) work on the principle of detecting a decrease in

acceleration of a moving vehicle and generate an electrical impulse. Figure is a schematic diagram of

an inertial sensor

Fig no: 3.3 Mass type sensor



3.2.2 Roller-type sensor

The roller-type sensor in fig no:3.4 involves a weight connected to a coil spring component.

Like the mass-type sensor, during impact with an oncoming vehicle, the metal weight is forced

forward which alters the tension on the coil spring to manipulate the electrical circuit that closes off

the sensor contact. It is important to note that the impact and safety sensors must activate and close off

at the same time to allow for deployment of the airbag

Fig no: 3.4 Roller-type sensor

3.3 AIRBAG CONTROL UNIT

Fig no: 3.5 Airbag control unit



The ECU in fig no: 3.5 is the main controlling unit or the brain of the entire passenger safety

system. The ECU not only sends the firing signal to all the air bags, but in the case of a smart air bag

system, it controls the force at which some of those air bags are deployed. These control units are part

of more advanced smart system that can sense whether the front passenger seat is empty, and if so, will

keep the passenger air bag from deploying. The ECU also sends the signal to seat belt pretension

devices and the rollover protection bars in convertibles. The control unit is constantly receiving

sensory input from sensors mounted around the vehicle and makes the necessary calculations to allow

it to deploy the appropriate safety systems. The ECU is typically mounted in the centre of the vehicle

in an area that provides the best protection. Some of the first generation units had capacitors that could

take approximately 20 – 30 minutes for the power to drain after the 12 volt battery was disconnected.

Today’s vehicles, however, have capacitors that drain within seconds. Care must still be taken,

however, during extrication operations to ensure that the ECU is not damaged; this could inadvertently

cause the ECU to deploy an air bag. An even more advanced system senses the weight of the front seat

passenger and can either deploy the air bag with more or less force, depending on the passenger’s

weight. One of the later amendments to the Federal Motor Vehicle Safety Standard 208 requires that

all vehicles manufactured after 2007 are required to be equipped with this type of system. The purpose

of this type of system is to perform one of two functions, depending on the vehicle: keep the front

passenger air bag from deploying if unoccupied, or sense the weight of the occupant in the front seat

and deploy the air bag with less force if the passenger is smaller or with greater force for a larger

person. Some systems are very simple and only sense the presence of a person on the seat, others can

differentiate between a child, small adult or large adult. This type of system, called an Occupant

Classification System or smart system, uses sensors in the seat along with dual stage or de-powered

frontal air bags. This smart system can also sense the severity of the crash using accelerometers, wheel

speed indicators, brake pressure sensors and impact sensors in the vehicles to deploy the air bags with

the appropriate force. Dual stage air bags are equipped two individual inflator units that can be

deployed individually or both at the same time. If the ECU determines that the occupant is a heavier

person or that the crash meets the criteria for a severe crash, both inflator units will fire. If the

occupant is a smaller person or the crash is less severe, it only ignites one of the inflator units, leaving

the second inflator unit un-deployed and loaded.

The danger with this type of system is that if only one of the frontal air bag inflator units has

been deployed, rescuers can falsely assume that that both air bags are no longer a threat. The fact is,

we can have an inflator that is still loaded and ready to deploy the air bag. The typical extrication

scenario has one of the two front seats empty. A rescuer, seeing a deployed air bag, thinks that the



vehicle is safe and enters the vehicle. The rescuer then places his or her knee on the unoccupied seat.

Now the ECU senses the rescuer’s weight and arms the second un-deployed inflator. The air bag, even

though it has already deployed, is now ready to deploy for a second time into the unsuspecting rescuer.

For this reason, it is especially important to disable the entire system by disconnecting the 12 volt

battery. Even if rescuers are able to disable the system, we must make every effort to keep ourselves

and any patients out of all air bag deployment zones.

Upon signal of a collision, the controller interprets the electrical input and measures the level of collision

to determine release of an airbag. In the event of one impact sensor and safety sensor being closed, an

electrical current is transmitted to an airbag module which contains the airbag and inflator assembly.

Activation of the airbag results in an ignition that produces an electrical transmission between a pair of metal

pins. The electrical arc created between both pins activates a propellant (made up of sodium azide) that starts

to burn and give off nitrogen gas, and it is this gas that starts to fill the airbag. The Volvo V40 model takes

airbag technology to a new level by deploying a pedestrian airbag upon impact on the bumper to this car.

Similar airbag control units currently on the market include a model introduced by TRW. This integrated

control module detects vehicle impact by using an occupant dynamic-based algorithm, which meets all North

American and European regulations with a rollover sensor adapting a functional system similar to the type

discussed in this article. The idea of an integrated airbag control unit has many advantages:

Increased sensitivity of the moving vehicle by placing the integrated control module in the

vehicle’s centre of gravity

Integrated crash sensors diversifies the diagnostics on a collision

Increased precision of the integrated sensor technology to allow for better safety

Cost-effective if all crash sensor systems are integrated into one module.

http://www.trw.com/sub_system/safety_electronics/airbag_control_unit_remote_sensor



CHAPTER 4

WORKING

The first stage of the airbag deployment is the accident itself. The collision, be it frontal or

lateral, activates an array of sensors in the vehicle, including accelerometers, impact sensors, side

pressure sensors, brake pressure sensors, and seat occupancy sensors. All these sensors are in intimate

connection with the ACU (Airbag Control Unit). The unit decides if and how to deploy the airbags.

When the ACU detects that the deployment threshold has been reached, it initiates the inflation stage.

As the compressed air system would have been impractical and quite inefficient, engineers came up

with an idea quite similar to the working principle of the solid rocket booster.

Each airbag incorporates a pyrotechnic device, known as an initiator or electric match,

consisting of an electrical conductor cocooned in combustible material. A current pulse heats up the

conductor, which in turn ignites the combustible material. This igniter triggers the chemical reaction

that actually fills the nylon fabric airbag with gas. The large volume of gas then forces the airbag out

of the steering wheel and/or dashboard at a speed of up to 200 mph or 322 mph, the whole process

taking about 0.04 seconds. Considering that the blink of an eye is approximated at 0.2 seconds, one

could say it's quite a speedy process The last stage of the airbag process is the deflation, which occurs

almost immediately after the inflation is completed. The gas escapes through special vents. They also

prevent the occupants from suffering major impact injuries. Another effect of the deflation is the

release of dust-like particles, mostly cornstarch and talcum powder that are used to lubricate the

airbag. Small amount of Sodium hydroxide may initially be present. This chemical can cause minor

irritation to the eyes and/or open wounds; however, with exposure to air, it quickly turns into Sodium

bicarbonate (common baking soda). Depending on the type of air bag system, potassium chloride (a

table salt substitute) may also be present. Initially, the chemicals used in airbags were a major health

concern, but present systems will only produce a mild irritation of the throat and eyes for most people,

as an outcome of dust released. Generally, these minor irritations continue up to the time occupant

remains in the vehicle with the windows closed and no ventilation. Once deployed, the air bag cannot

be reused and should be replaced by an authorized service department.



CHAPTER 5

AIRBAG TYPES

With each new generation of vehicles coming out on the market, rescuers are finding that these

vehicles are being equipped with more airbags. All of these air bags are designed with a specific

purpose and function but when used in conjunction with the other safety systems, increase the

survivability of all occupants involved in a vehicle accident. In this section, we will discuss the

different types of air bags, the intended function and the danger that they present to rescuers.

5.1 FRONTAL AIR BAGS

Fig no: 5.1 Driver side airbag

These are the most prevalent and familiar air bags on vehicles. Fig no:5.1 shows Driver side

airbag This is the only type of air bag that is on every vehicle that is equipped with air bags. There may

not be a head curtain air bag or side impact bags, but if the vehicle has air bags, it will be equipped

with frontal air bags. The purpose of the frontal air bag is to prevent any front seat occupant from

impacting the steering wheel or dash board in the event of a frontal collision. The first version of the

frontal air bag was a single stage air bag with only one firing unit. It provided an added measure of

safety for all passengers but created a hazardous situation for shorter drivers. In order for the frontal air

bag to be effective, it has to have enough room to fully deploy prior to the driver impacting the bag.

This ensured that the air bag’s deployment energy was completely dissipated before the patient came

into contact with the airbag. Obviously, a shorter driver has to move the driver’s seat closer to the

steering wheel in order to drive. This proved to be very dangerous and sometimes fatal. The driver

usually made contact with an air bag prior to complete deployment and absorbed a lot of the energy.

This is the point where injuries and fatalities occurred, usually due to brain damage or fractured

cervical vertebrae. Another danger with first generation frontal air bags is that they were extremely



unreliable. That, coupled with the fact that some did not have any labelling or identification gave Resc-

uers the idea that these airbags were not present. If the 12 volt battery was not disconnected, the

system remained armed. To combat these hazards, an amendment to FMVSS 208 mandated that

vehicles manufactured in 2007 and later be equipped with an Occupant Classification System to work

in conjunction with dual stage or de-powered frontal air bags, as discussed before in the Electrical

Control Unit section. Some older model vehicles were equipped with this system long before the

standard dictated. These air bags, however, are difficult if not impossible to differentiate from single

stage air bags. The rescuer will not know whether the deployed frontal air bag is a single or dual stage

type. The following pictures illustrate some frontal airbags. Here we have a typical un-deployed

steering wheel mounted single stage frontal air bag.

Fig no: 5.2 shows the deployed first stage of a air bag

5.2 HEAD PROTECTION BAGS

One of the first types of head protection to be introduced in the US was the (HPS) Head

Protection System in the 1998 BMW, also known as the (ITS) Inflatable Tubular Structure. These are

much different than the curtain airbags we see in most vehicles. This tube is anchored at the

pressurized cylinder that is mounted on the lower portion of the post and at the rear to the roof rail

behind the post, allowing it to deploy diagonally across the window opening. The bag is stored inside

the trim of the post, along the headliner trim over each door. When un-deployed, the only identifying

markings are the letters 'HPS' embedded in the trim cover at the top of the posts. Unlike other airbags,

the tubular bag consists of a specifically designed material that is woven in a pattern that expands as

the bag deploys to form an airtight tube. Also unlike most airbags, the tube does not deflate; there are

no vent holes that allow the gas to escape. The tube will actually remain inflated for hours after the

collision. The tube remains firmly inflated to offer head protection from rebound forces, which are

common in side impacts and rollovers. Once the door is opened, rescuers can safely puncture the tube

and cut the mounting strap at the post to get the bag out of their way. The bag is approximately 38

inches long and 5 inches in diameter when inflated. Nylon web straps are sewn into each end of the



Fig 5.3 Head protection airbags

bag to attach it to the vehicle. Like all side impact airbags these cannot deploy a second time. If the

tube is not deployed rescuers must not only stay out of the deployment zone of the tube, but the whole

door area. These tubes are always used in conjunction with a torso type door or seat mounted airbag.

The gas inflator is located at the front end of the system. The canister which is filled with nitrogen,

argon or other inert gas is mounted in the dash at the lower pillar area. These systems will deploy if the

sensor experiences an impact of about 12 mph or above. As stated before the cylinder of a tube can

always be found in the lower portion of the post. This location is in close proximity to where we will

make relief cuts for the different dash displacement evolutions. It is imperative that we make sure to

peel all the plastic from this area to ensure that we do not cut through these cylinders.

5.2.1 Side curtain airbags

The two most commonly used curtain airbags are the front window type and the full length

type. The front window curtain usually extends from the post to post and extends down from the roof

to about the top of the door panel .The full length curtain usually extends from just behind the A post

to post and extends from the roof to the top of the door panel also. Like the head protection tube, both

of these are hidden behind the trim panels and head liner, when undeployed they can only be detected

by small emblems embedded in the trim panels. Rescuers must be aware that these emblems only

indicate the presence of a head curtain bag, not the location. These bags are deployed by small stored

gas inflators that can be located at the front, centre, rear, or anywhere along the support system. They

are found in the post, along the roof rails, in the posts and some even over the rear glass. It is

extremely important that these inflators be visually located before any extrication procedures begin.

Unlike the solid propellant gas canister built into the passenger’s frontal airbag, these inflators have no

protection around them; they are simply a long thin tube that is filled with a compressed inert gas.



Fig no: 5.4 Side curtain airbags

Some vehicles, such as the Volvo XC90, Infinity QSX, Nissan Pathfinder, Armada and Quest

minivan, and Ford Excursion have head curtains in two sections, requiring two cylinders to deploy the

curtain. Again, it becomes extremely important to expose as much of the plastic as possible prior to

beginning any evolutions.

5.3 SIDE IMPACT AIRBAGS

Fig no: 5.5 Side impact airbags

Side impact air bags fig no:5.5 are designed to protect a passenger’s head and thorax with

some style of bags or just the thorax with another type of bag. Some of these bags are designed to help

keep an occupant from being ejected from a vehicle in a roll over. Like the frontal airbags; side impact

airbags must have a crash sensor to recognize that a crash has occurred. These sensors are usually

mounted in the frond door, the post, or most are located inside the rocker panel just below the post.

The cylinders for these bags can be mounted in the post and also underneath the folded air bag in the

seat back. Some older vehicles used the same chemical propellant, sodium azide, used in frontal air

bags. The air bags can be mounted in one of two locations: the door or the out board side of the seat



back. The door mounted bags can either mounted on the inside of the door and deploy from a blow out

panel. Some newer door mounted bags pop up, like a toaster, from the top of the door. The 2010 Volvo

C70c1920c on vertible has an air bag that extends the entire length of the passenger compartment,

from the post to the rear of the passenger compartment. This bag is extremely rigid so that it can

provide the necessary head protection, even without a roof. These bags obviously present a danger to

rescuers who are leaning over the door of a car that has not had the battery disconnected. Side impact

bags that are mounted in the seat are usually powered by high pressure cylinders. Some older cars,

however, still use chemical propellants. As stated before the cylinders can be mounted in the posts of

the vehicle or in that actual seat back itself, usually under the folded air bag.

The seat mounted bag is usually placed under the seat fabric in the out board side of the seat. It

can either come out of a blow out panel or from a pre stressed seam in the fabric that is designed to

tear open on air bag deployment. The danger with this type of air bag is its deployment path. The

normal path is to first deploy outwards before it goes forward. The bag uses the closed door to rebound

inward changing the direction of the bag. If a door is opened or has been removed, a rescuer standing

in the door way may think that he is out of the deployment zone, but due to the bags deployment path,

might be placing him or herself in danger.

5.4 OCCUPANT POSITIONING AIR BAGS

Occupant positioning air bags are different bags placed throughout the vehicle that work

together, along with the seat belt and pretensioner, and have the sole purpose of keeping front seat

occupants from sliding out of the seat in a front end collision. In this type of collision, a person in the

front seat usually slides out of their seat and is thrown under the dash if this system is not in place.

This is known as submarine and usually meant significant injury or death to the occupant. Some

vehicles may have some or all of these types of bags and some vehicles may not be equipped with any

at all. All of these bags present their own unique dangers that we will now discuss.

5.4.1 Knee bags or bolsters

These bags fig no:5.6 deploy exactly where their name suggests. They are usually placed under

the steering column and under the passenger side dash board. They function not only as part of the

Occupant Positioning System, they also reduce the severe knee and hip injuries that normally occur

During a front end collision. These bags, as well as the others we will discuss, work in conjunction to

keep the occupant in their seat. There are two basic types of bags: the knee bag and the knee bolster.

Both serve the same purpose. The knee bag is just a simple air bag that deploys outward from the dash

toward the front edge of the seat. These bags are usually powered by the same firing units and the



propellants (sodium-azide) as the frontal air bags and are usually identified on the blow out panel. The

picture shows an identification stamp. On the right is a picture of a deployed knee bag.

Fig no: 5.6 left shows an identification stamp. On the right is a picture of a deployed knee bag.

5.5 CARPET BAGS

Carpet bags in fig no:5.7are mounted in the floor board of the vehicle and use the same sensors

as frontal air bags. These air bags deploy using a pressurized gas cylinder that is usually mounted over

the centre tunnel. The purpose of this bag is to push the occupant’s feet up, thereby slightly changing

the angle of the occupant’s legs. This slight change of angle in the legs will help keep the patient from

sliding out of the seat and under the dash. The danger comes more from where the pressurized cylinder

is mounted. Rescuers may not expect that cylinder is in the centre tunnel and cut through it or weaken

it during operations

.

Fig no: 5.7 Picture of a deployed carpet bag

5.6 ANTI-SLIDE SEAT BAGS

The anti-slide seat bag in fig no:5.8 is one of newest bags to be installed in vehicles. It is not

actually a bag, but instead a thin metal envelop structure that is mounted under the foam cushion of the



seat. The operating principle of this bag is similar to an airbag except that the bag never comes in

contact with the occupant. The bag operates in two stages upon receiving the firing signal from the

ECU: First, a gas generator inflates the metallic envelope which pushes the foam up in the front edge

of the seat. This action pushes the occupant back and against the seat back. Second, a deflation

controller beneath the module slowly deflates the envelope and causes the metal envelope to form to

the shape of the pelvis. This forms a pocket in the seat to hold the occupant in position, forming a

protective shield around the pelvis. It also assists the carpet bag in lifting the weight of the occupants

legs preventing the downward force of the feet pushing into the floor. With this bag, the obvious

danger occurs when a rescuer places his or her knee on a seat with an un-deployed bag.

Fig no: 5.8 Anti-slide Seat bag

5.7 MISCELLANEOUS AIRBAGS

In this section in fig no: 5.9 we will illustrate what the rescuer has in store for him as far as the

future of the air bag. The direction of seat belt technology shows us that the possibility of air bags and

their locations is limitless.

Fig no: 5.9 Air bag in the head rest of the rear seat in a passenger car.



Fig no: 5.10 Air bag installed in the seat belt.

Not all air bags will be inside the patient compartment. Soon, rescuers will be faced with hood, front

bumper and/or windshield air bags.

Fig no: 5.11 Pedestrians protection airbags

The Jaguar XK fig no:5.11 has 2 airbags under the hood that help to protect pedestrians by cushioning

the hood and decreasing the impact force into the windshield. Ford will soon be unveiling a bumper

and windshield air bag that is designed to protect the pedestrian from impacting the bumper and hood.

The windshield bag will decrease the force of impact with the windshield while assisting in vaulting

the patient over the windshield and roof of the car.



Fig no: 5.12 This air bag to deflect the path of the rider up and

over the impacted vehicle

Air bags will not only be seen in cars, they will also be installed on motorcycles as well. This air bag is

designed in fig no:5.12 to deflect the path of the rider up and over the impacted vehicle. Before, the

rider would fly directly into the vehicle causing fatal head and neck injuries

Fig no: 5.13 Airbag vest is available to motorcycle riders



An airbag vest in fig no:5.13 is available to motorcycle riders to give protection to the head and upper

torso in a crash. The vest is only effective if the rider is wearing a helmet. As we have clearly seen, air

bags present a very real danger to both rescuers and patients during extrication operations, regardless if

they have deployed. The most important thing to take away from this is to always operate as if you are

surrounded by live and loaded air bags. Vehicle manufacturers have installed safety devices in an

attempt to prevent accidental deployment but we should not and cannot depend on those devices to be

operational after an accident. Even if the vehicle has been stabilized and the battery has been

disconnected, you must protect yourself, your crew and your patient from the possibility of being

impacted by an air bag.



CHAPTER 6

AIRBAG RISKS

6.1 AIR BAG CONTACT INJURIES

Air bags must inflate very rapidly to be effective, and therefore come out of the steering wheel

hub or instrumental panel with considerable force, generally at a speed over 100 mph. Due to this very

high initial force, contact with a deploying air bag may cause injury. Properly restraint occupant along

with applied due seat belt receives very minor abrasion or burns. However, very serious or fatal

injuries can occur when someone is very close to, or in direct contact with an air bag module when the

air bag deploys. Even never attach objects to an air bag module or place loose objects on or near an air

bag module, since they can be propelled with great force by a deploying air bag, potentially cause

serious or fatal injuries. Thus safety restraint system must be utilized with due care and regulation to

get best results. An unrestrained or improperly restraint occupant can be seriously injured or killed by

a deploying air bag. The National Highway Traffic Safety Administration (NHTSA) recommended

certain rules for the safety of occupant and passengers.

They are as follows:

Never put a rear-facing infant restraint in the front seat of a vehicle with a front passenger air

bag.

Children of age 12 and under should be properly restrained in a rear seat.

Driver should sit with at least 10 inches between the centre of their chest bone and the steering

wheel.

Always apply seat belt, it retain occupant and passenger rightly positioned and minimizes risk

of serious injuries.



CHAPTER 7

CONCLUSION

The air bags are of greater importance in today’s vehicles since safety of human life is of prior

importance. Since the count of automobiles is increasing tremendously on our roads, the probability of

accidents is also more. So far a safe riding and for saving the precious life the safety bags must be

implemented. Today it is the privilege of the high class people who own high priced cars. Let’s hope

every automobile manufacturer implement the same since safety for life is inevitable. The number of

persons killed or injured in traffic has dropped continuously since the development of air bag system.

Over the time, the development of seat belt becomes an indisputable matter of course. Today, the 3-

point automatic seat belt, seat belt tensioner and airbag constitute a carefully matched passenger

protection system. Implementation of these safety restraint systems with due care and regulation can

further drop the fatality rate and serious injuries at the time of road accidents


Dept. of Mechanical Engg. XXXVI

AXIS CET

CHAPTER 8

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Science

SEMI REPORT ON AIRBAG SYS