The official Danish environmental rules state: If you cast in an enclosed box, and your fan is able to move 1.800 cubic metre of air per square metre of working area per hour this creates the required air flow of 0,5 m/s away from the worker.

We are doing this with a 5 bladed Multifan, Ø 40 mm, pitch angle 35 degrees,1400 rpm, producing 4200 m3/hour at 30 mm resistance for our 2 casting tables. This requires 250 W of power, but our motor is 700 W, as this was the most priceworthy option in the flameproof version. It does, however, not consume much more that 250 W and has a lower starting current.