Float
This may be air filled or rigid and has the purpose of maintaining the correct orientation of the equipment on the water, establishing freeboard in order to minimise the loss of oil over the boom. Float materials are air, foam, bubble rap, cork, etc. Designed to float the boom even with some load or tension. When inflated all caps should be replace, trash can get into valves and release air.
In some cases the float material used is bubble rap, these floats have been cut out of booms to be used as pillows in some poor areas of the world.
Freeboard
This is the minimum vertical height of the boom above the water line to the top of the float section. It prevents oil from being washed over the boom. If it is too high it may be pushed over by high winds. In open water the boom must maintain its freeboard in waves. It must be flexible enought to rise and fall with the waves so that the freeboard is not lost.
Skirt
The continuous portion below the water, which has the purpose of containing the oil. To some degree the deeper the skirt the more effedtive it is however there is a optimum skirt depth for different applications. Since the forces acting on the skirt are proportional to the skirt area. Increasing the skirt depth to what is really necessary put heavy loads on the tension member.
The distance measured from the water line to the lower limit of the skirt is called the draft.
In shallow water it should be mentioned that the skirt should not take up more than 20% of the water depth as it causes and increase in current velocity which will drag the boom under the water with the oil flowing over the top or in other cases especially near the shoreline encourage oil to flow under the boom.
Ballast
Is weight added to the bottom of the skirt to maintain the barrier in a position perpendicular to the surface of the water and in some cases to provide the tension member for the boom.
Some manufacturers use, Steel or lead weights, water, may be used. These weights are very often cut from booms by fishermen. Below is a guideline for the weight of ballast dependent on boom size.