There are three reactions involved in the deployment of an air bag. Those reactions are listed above.
Sodium Azide, Potassium Nitrate, Silicon Dioxide are the initial reactants packed into the air bag module. 3.38 moles of sodium azide must be packed into the air bag module for the air bag to inflate(PV=nRT P=1.2 atm, v=70L R= .0821 L atm K-1 mol-1 T=30+273). The decomposition of the sodium azide yeilds 3.3 moles of Nitrogen gas (PV=nRT P=1.2 atm, v=70L R= .0821 L atm K-1 mol-1 T=30+273) 2.7 grams of sodium are produced it the first reaction. 2 grams of potassium nitrate are needed to completely react with the sodium (from the first reaction) in the second reaction.
Safety of reactants and products
N2:The reaction produces harmless nitrogen gas that fills the airbag. While it is coming out the nitrogen gas expands and undergoes a process that lowers down the temperature and removes the combustion.
NaN3: When the impact has detected the NaN3 is electrically initiated. It decomposes very rapidly to produce sodium metal and nitrogen gas.
Na: Reacts to remove harmful products, reacts violently with water
K2O: Reacts with the third compound of the original airbag mixture, silicon dioxide, to form alkaline silicate that is harmlessly discarded in a deployed airbag.
Sodium silicate glass: A stable unreactive substance
Stoichiomety is very important to the PROPER function of airbags. With out the careful calculations and measurements airbags a life saving device would be life threatening.