Dispersants are applied from boats that are usually equipped with specialised spray arms. If spray arms are not available, fire hoses or monitors are sometimes used to apply diluted concentrate dispersants. However, the very high flow rate makes it difficult to achieve optimum dilution of the dispersant and uniform application of the dispersant difficult.
Vessels offer certain advantages for dispersant spraying. They are usually readily available and are easy to load and deploy. They have cost advantages over aircraft and can apply dispersant fairly accurately to specific areas of a slick. However, vessels also have serious limitations, particularly for larger spills. The area of oil that can be treated and the rate of dispersant application are both relatively low in comparison to larger aircraft, and it can be difficult to locate the heaviest concentrations of oil from the bridge of a vessel.
Aerial dispersant application offers significant advantages over vessels. Aircraft allow a rapid response, good visibility, high treatment rates and optimum dispersant use. In addition, aircraft can be used to treat spills further offshore.
Dispersant can be applied from specially designed aircraft, or from agricultural or pest control spray planes which require minor modification. Several types of helicopter have also been adapted to spray dispersants, and most are able to carry underslung bucket spray systems without modification. Aircraft selection will depend on the size and location of the spill, although in reality local availability will often be the crucial factor. The endurance, fuel consumption, turnaround time, payload and ability to operate from short or improvised landing strips are all important factors to consider.
Once bulk oil has been removed from affected shorelines, dispersants are sometimes used as cleaning agents during the final stages of clean-up to remove the remaining oil from hard surfaces such as rocks, sea walls, and other man-made structures. The dispersed oil cannot be collected, and for this reason, dispersant use on the shoreline is restricted to areas of low environmental concern but high amenity value. Shoreline cleaners, specifically formulated for the task, may often provide a better alternative.