Do you know the reason that coffee bag with hole?

FINE, is a coffee packaging bags manufacturer in China. Saying of coffee bag, I want to share you some tech of coffee or its packaging bag.
If you've ever purchased a bag of specialty grade coffee, you might notice a small pin hole located somewhere your bag. Do you know why the hole exist? Occasionally when people grab a bag of coffee, they'll squeeze the bag with their nose near it to get a whiff of the goods inside. Believe it or not, that's not just a "smelling hole" as I've heard it referred to before.
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. The other option is to let the coffee rest outside of a container. However, oxygen is the enemy of fresh roasted coffee. By allowing the coffee to be exposed to air for an extended period of time, it accelerates the staling process of the coffee. So, what can be done to retain the coffees freshness while allowing it to naturally de-gas? That's where the one-way valve comes into play.
That valve on your bag allows for the carbon dioxide to escape from inside the bag without allowing oxygen to enter the sealed bag. This valve increases flexibility for the roasters and allows us to immediately package the coffee without worry of the bag bursting on the shelf or in transit to the customer. Most of the canned coffee found on your grocery store shelf is ground & allowed to de-gas for an extended period of prior to being packaged and sealed. In other words, the coffee is stale before it's even sealed. Not good for the quality of the coffee & has a huge negative impact on your morning brew. We package all our coffee in foil-lined bags with a one-way valve. Our packaging provides an excellent barrier to the environment and helps retain the quality of your coffee for an extended period of time.
In conclusion, the next time you put your nose close to your coffee packaging bag to smell the contents inside, remember that small device is working day & night to keep your coffee fresh longer. Be blessed.