Subject: What is the reaction that fills an automobile airbag?

An activity that I do with my class is to have them design an airbag using 
a ziplock bag and the reaction between baking soda and acid.  As part of 
the introduction to this lab I give what I believe to be the reaction (the 
decomposition of sodium azide).  My brother (a mechanic) says I am wrong; 
however, he doesn't know the correct reaction.  If I am right, how do they 
handle the safety problems associated with sodium metal?
               2NaN3  --> 2N2 + 2Na

Re: What is the reaction that fills an automobile airbag?