Some EdgeStar, Koldfront, and AVALLON wine coolers and beverage coolers use a carbon filter at the back of the unit to keep the air inside the unit smelling fresh. It is recommended that you replace that filter every 6 to 12 months. If your unit has the circle style filter, it simply turns 90 degrees counter clockwise to unlock and then pulls straight out. Installation is just pushing the filter in and turning it 90 degrees clockwise to lock it in. Sometimes, those filters are hard to get a grip on. You can use some needle nose pliers to help you out. There is a picture below as an example: