Containment booms, or simply booms, are the basic and most frequently used piece of equipment for containing an oil spill on water. Booms are generally the first equipment mobilized at a spill and are often used throughout the operation. This chapter covers the types of booms, their construction, and operating principles and uses, as well as how and why they fail. It also covers ancillary equipment used with booms, sorbent booms, and special purpose and improvised booms. The topic of fire-resistant booms for use when burning oil on water is covered in Chapter 10.