Bonn Agreement Oil Appearance Code

The Bonn Agreement Oil Appearance Code: A Comprehensive Guide

Oil spills are hazardous events that have significant environmental, economic, and social impacts. In response to this threat, the International Convention on Oil Pollution Preparedness, Response, and Cooperation (OPRC) was adopted in 1990. The Bonn Agreement, a regional agreement between the governments of the United Kingdom, France, Belgium, the Netherlands, Germany, and Denmark, is a key player in implementing this convention. The Bonn Agreement has developed a framework for dealing with oil spills in the North Sea and the English Channel. One of the most important elements of this framework is the Oil Appearance Code.

What is the Oil Appearance Code?

The Oil Appearance Code is a system for classifying oil spills according to their visual appearance. It is a critical tool used by experts to determine the type of oil involved in a spill and to guide the selection of response strategies. The code is designed to categorize oils into four classes based on their appearance in seawater:

Class I: A light, non-persistent oil that disappears easily when agitated.

Class II: A medium-weight oil that may persist for several days in the environment.

Class III: A heavy oil that is likely to have a significant impact on the environment.

Class IV: A thick, viscous oil that is extremely persistent and challenging to clean up.

Why is the Oil Appearance Code important?

The primary benefit of the Oil Appearance Code is that it allows responders to determine the type of oil involved in a spill and make informed decisions about how to clean it up. The code helps to ensure that response efforts are appropriate, proportionate, and effective. By classifying oils based on their visual appearance, responders can quickly identify the type of oil and develop a targeted response.

Another benefit of the Oil Appearance Code is that it supports international coordination in the event of an oil spill. The code is recognized and used by many countries, which allows for a coordinated response and the sharing of best practices across borders. This cooperation is critical in the event of a major spill that affects multiple countries.

How is the Oil Appearance Code determined?

The Oil Appearance Code is based on the physical and chemical properties of the oil, including viscosity, density, and volatility. The code is primarily determined by visual observations of the oil in seawater. A trained observer will review the appearance of the oil and compare it to the standard classification. In some cases, laboratory testing may be required to confirm the classification.

What are the limitations of the Oil Appearance Code?

It is essential to recognize that the Oil Appearance Code is not a perfect system. The code is based on visual observation and may not always be accurate, particularly if the oil is mixed with other substances such as water or sediment. Additionally, the code does not account for the potential toxicity of the oil, which can vary significantly. Therefore, the code should be used as a guide, and other factors should be considered when developing a response strategy.


The Bonn Agreement`s Oil Appearance Code is a crucial tool in responding to oil spills in the North Sea and the English Channel. It allows responders to determine the type of oil involved in a spill quickly and develop a targeted response to minimize the impact on the environment. While the code has limitations, it is widely recognized and used, making it an essential component of international efforts to prevent and respond to oil spills.