### Instruction:
Why do potato chip bags become stale after opening?

### Response:
Potato chip bags are filled with nitrogen! Many consumers think the chip companies are out there to get your money by filling three quarters of your bag with air, but it’s actually nitrogen to keep your chips fresh. This is why once you open the bag, you should finish the chips as soon as possible. There, now you have a reason to finish the whole bag of chips in one go without feeling guilty.