These metal boxes with radiant tube fans inside of them come in different sizes. Starting with a mere 250 m³ up to 7000 m³. The metal boxes are ideal in a dry place where they will not be affected by corrosion. These boxes are a bit cheaper than the other options like MDF or Birch boxes. We also have several plenumboxes. These are boxes that form a connection between an air grid and a ventilation duct.