For decades, many international and country sponsored agencies, as well as many multinational oil companies, have developed a raft of requirements, guidelines and recommendations regarding marine vessels, oil equipment and personnel safety that operate in cold and/or polar ice-covered waters. 

Although there is no single international standard, the DNV GL standard DNVGL-OS-A201 includes one of the most comprehensive set of principles for winterization of systems, equipment and vessels. The standard uses a three-tiered approach: 

1. Winterization requirements are based upon fulfilling the stated functional requirements. These provide the rationale and intent behind any particular winterization issue.
2. Some functional requirements are further supported by performance requirements. These explain the type of performance a winterization measure should achieve in order to fulfill the intent of the functional requirement in greater detail.
3. Functional and performance requirements are supported by prescriptive rules and guidance notes to provide a set of generally acceptable solutions to meet the functional and performance requirements.

Winterization requirements can be broken into two classes: anti-icing and de-icing. Anti-icing is the prevention of ice formation. Anti-icing requirements are generally related to personnel safety while de-icing requirements are to prevent excessive ice loading. Since anti-icing and de-icing measures can vary, DNVGL-OS-A201 defines specific winterization temperature conditions as one of three categories: Basic, Cold and Polar. These three categories depend on Indicative Winterization Temperature and Sea Water Temperature. 

DNVGL-OS-A201 also contains the requirements for materials, stability, hull equipment, electrical, safety, navigation, machinery and telecommunications. DNVGL-OS-A201 has broken this down into two key categories: Cat I and Cat II. Cat I includes winterization principles for navigation, steering, propulsion, anchoring and lifesaving/escape routes. Principles for Cat I generally revolve around anti-icing techniques. Cat II lists out winterization principles for decks and superstructures, helicopter decks, railings and cargo areas. Principles for Cat II, on the other hand, are connected to de-icing techniques. 

These standards for vessels are widely accepted around the globe for offshore and marine environments, particularly for cold-climate conditions. The use of these techniques can greatly help optimize winterization efforts.