Re: How is the potato chips bag sealed ?.

Modern packaging has come a long way from placing items in a polyethylene 
bag and heat sealing the top.  Many packages are made up of three or more 
laminated films, depending upon the particular application.  One layer 
might be aluminum to act as an oxygen barrier.  Other layers might include 
polyethylene, polypropylene, Mylar, etc.  www.packagingdigest.com is a 
trade publication that provides links to packaging materials and machinery. 
 In the trade, machinery that seals bags is referred to a "form, fill, seal" 
equipment.

It appears that most packages are still sealed by heat; the inner layer of 
the package is usually designed to melt and bond to its counterpart when 
subjected to heat and pressure.  A company, CP converters  
http://www.cpconverters.com/Markets/nuts.htm offers packages that can be 
nitrogen sealed (in this case to extend the shelf life of packaged nuts.  
So the technology to seal products in pouches in nitrogen is certainly 
available in the market.