Ona Carbon-Air (without gel or filter)ONA Carbon Air is the latest in environmentally friendly odor control! The ONA Carbon Air unit has two 6 inch ports to facilitate airflow into the carbon filter and out through the fan unit. You simply connect the ONA Carbon Air to your existing ventilation system to distribute throughout your room or air exhaust system. A pail of ONA gel attaches securely to the bottom of the Carbon Air unit. The ONA Carbon Air unit is to be used exclusively with ONA