Extract air box - for valve above door

In renovation projects it is often impossible to mount extract air valves in the ceiling due to a lack of space. You can use e.g., the entrance hall as distribution room by dropping the ceiling and placing extract air above the doors to the rooms from which you want to extract humid and vitiated air.    

For this solution you can use NilAIR extract air boxes for valves above doors. The boxes are available with 2 or 3 spouts depending on the air volume required.