A dehumidifier removes humid from the air whenever humidity levels become too high. Your grow room can get too humid when your light cycle is shortened. Use a dehumidifier to prevent bud rot and other molds.

Learn all about humidity and your grow room:

• Humidity And Marijuana Plants

More climate related terms:

Climate | Air circulation | Airtight | Charcoal filter | Extractor | Fancontroler | Fans | Hygrometer | Humidistat | Humidifier | Heating