An EO sticker, or emissions sticker, is required in order to operate a cold air intake on your vehicle. The process of getting an EO sticker can vary depending on the state in which you live. Some states require that you have your cold air intake professionally installed, while others may allow you to install it yourself as long as you meet certain requirements. In either case, you will need to submit an application and supporting documentation to your local DMV or environmental office. Once your application has been approved, you will be issued an EO sticker that must be affixed to your cold air intake.