Actually, there are no any ordinary air in a bag of chips. All of the air (oxygen) is removed and replaced with nitrogen gas (this process is called nitrogen flushing). Nitrogen does not affect the taste of the chips or react with the chips like oxygen does. This increases the shelf life of the chips. The nitrogen gas fills up the bag, so the contents inside are protected during shipping. If the bags were filled with oxygen it could have spoiled the product and made it soggy.

More Info: