If you consider yourself a coffee connoisseur or you just like the fresh-roasted house blend from your local coffee shop, chances are you have a bag of beans or grounds in your pantry right now.

But, have you ever noticed the small hole a few inches from the top? Turns out, it has an important purpose. It’s not just a hole—it’s a valve.

When your coffee goes through the roasting process, it releases carbon dioxide. Coffee roasters want their beans to get into bags and shipped out as quickly as possible. The fresher the better, right? That means some carbon dioxide still remains even after it’s bagged.

If fresh beans or grounds were placed into a bag without a valve (hole), the leftover carbon dioxide would have no way to escape. The bag would start to swell. If there was any moisture inside, that could create condensation and potentially compromise your brew.

The valve allows for enough of that gas to escape while the bag stays nice and tight, and the beans don’t spoil.

Plus, if you give the bag a gentle squeeze, you can get a whiff of the wonderful roasted aroma and know what to expect when you brew it.

The lingering carbon dioxide can last for about two weeks, so whether you’re getting a freshly-roasted bag from a nearby cafe or picking one up from the grocery store shelf, be thankful for that little hole, and that your coffee is staying fresher and de-gassed because of it.