The Naber Thermobox is an innovative warmth restraint system, which offers high quality, functionality and ecology. The Thermobox is mounted into the inside of an extractor hood. If the hood is not working, the Thermobox prevents loss of flow and warmth. The innovation: the closed system creates two fully isolated air chambers. The Thermobox works mechanically without the need for additional use of power. It opens and closes by using a magnetic system. Its heat transition coefficient, the so-called U-value, is in the same category as the one of insulation-glazed windows.