A curtain boom has a large round foam or air buoyancy chamber floating on water with a single piece of chain weighted fabric (PVC or polyurethane) extending under water. Boom sections are usually 15 metres long with buoyancy chamber diameters ranging from 100mm to 850mm. approximately 40% of the boom is above the water and 60% below.

The larger the buoyancy chamber and underwater skirt depth the rougher the sea conditions in which the boom can function.  Foam filled curtain booms do not usually exceed 300mm diameter because of the storage space required.  Permanently deployed boom as the name suggests, is installed for long periods of time. Its position in the water can be moved easily but it is not often recovered and stored.  Special connectors on the ends of all booms allow multiple boom sections to be easily joined together.