SIS is third-party inspection agency (TPIA or TPI) is a organization, complying with the ISO, ASME, API, BS, JIS and other global standards. Third-party inspection or "Category A" is the most stringent of the 3 categories of inspection organizations that the standard specifies. Based on this requirement, the third-party inspection agencies / companies and parties such as buyers, sellers, engineering companies, plant owners must have access to these agencies and use their services. Confidentiality, independence, impartiality, and integrity are important conditions for being a third-party inspection agency.