• Certificate of successful completion of studies in a technical or scientific field at a university, college or university of applied sciences
• For proof of personal reliability:

• If you are resident in Germany, you will generally need a certificate of good conduct for submission to an authority (document type O)
• If you are resident abroad, you will need documents from your home country to prove that you are personally reliable enough to perform the desired service.

• Certificate as proof of training as an expert in accordance with DVGW Code of Practice G 100 or proof of membership of an accredited inspection body (e.g. TÜV, MPA or ZÜS) for inspecting the technical safety of high-pressure gas pipelines in accordance with the High-Pressure Gas Pipeline Ordinance (Gashochdruckleitungsverordnung)
• Declaration by the employer(s) that the expert to be recognized is in active employment and that he/she is free from instructions from his/her superior or employer in the performance of his/her inspection activities,
• valid, personal or monitoring organization-related proof of liability insurance that protects the expert against possible claims for damages arising from their expert activities (personal injury, property damage and financial loss)
• Proof of regular participation in further training and subject-related exchange of experience

When checking personal reliability, the approving authority may, in addition to the documents listed, also request other documents in individual cases that are suitable for making a statement about the personal reliability of the applicant.