title_body: Why do coffee packs have an aroma hole if it is recommended to store coffee in an air tight container
upvoted_answer: It's actually a one-way valve &amp; it's critical to the shelf life of the coffee and the preservation of the bag itself.
  When coffee is fresh roasted, it releases carbon dioxide. It's basically a by-product of the roasting process. When the coffee is ground, carbon dioxide is released expeditiously. If you simply place fresh roasted coffee in a completely sealed bag, the bag will expand and in most cases rupture.
  
  http://beanfruit.com/blogs/news/15152773-whats-that-thing-on-my-coffee-bag