ISO 16975-3:2017 specifies guidance on how to conduct fit testing of tight-fitting respiratory protective device (RPD) and on appropriate methods to be used. Fit testing is only one element of a complete RPD programme. The intention of fit testing is to evaluate the effectiveness of the seal between the wearer's face and the respiratory interface (RI). A complete RPD programme is defined in ISO/TS 16975‑1. ISO 16975-3:2017 specifies requirements for conducting RPD fit testing and includes - qualifications/competences of fit-test operators, - specific fit-testing procedures, - interpretation of fit-test results, and - record keeping. A fit test is not required for escape-only RPD.