In 2001 the Working Group (WG) "Safety" was created within the European COST Action B14 "Hyperbaric Oxygen Therapy" with the main objectives to elaborate recommendations of good practice for hyperbaric medicine and to follow the European normalisation process of hyperbaric chambers. During three years of preparation of the European Code of Good Practice (ECGP) for HBO, the relevant documents concerning safety in hyperbaric chambers from each European country have been revised. The initial document drew on the BHA "Health and Safety for Therapeutic Hyperbaric Facilities: A Code-of Practice" (2000), and later on it was modified using national regulations and standards (from Belgium, Finland, France, Germany, Greece, Italy, Portugal, and Spain), as well as European Norms and existing experience from experts of hyperbaric centres, committees, professional and scientific associations. The ECGP for HBO consists of chapters dedicated to staffing (including responsibilities, competencies and education, minimum team during hyperbaric sessions, fitness and health surveillance), equipment, gas supply, risk management and procedures (including standard and emergency operating procedures, maintenance, record keeping, and patient safety). It also includes ECHM Educational and Training Standards for the Staff of Hyperbaric Centres (1997), ECHM Recommendation for Safety in Multiplace Medical Hyperbaric Chambers (1998), as well as COST B14 Working Group "Technical Aspects" Final Report (2001) including a risk analysis conducted specifically for therapeutic hyperbaric facilities. Many efforts have been spent to make the ECGP for HBO compatible with the new project of the European Norm prEN 14931 "Pressure vessels for human occupancy (PVHO)--Multiplace pressure chamber system for hyperbaric therapy--Performance, safety requirements and testing", which has been prepared at the same time by the CEN/BT/TF 127. Both groups (CEN/BT/TF 127 and COST B14 WG "Safety") cooperated extensively in the field of safety aspects of using hyperbaric chambers as medical devices, and both final versions of documents include many cross references. Being prepared by international Working Group "Safety" and after acceptation by all members of the COST B14 action, the ECGP for HBO represents a harmonised European view on safety in therapeutic hyperbaric facilities and can be used as a reference document for European countries for Guidelines, Regulations, and Standards in hyperbaric medicine.