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What is the QSTI/QSTO Program


The Qualified Source Testing Individual (QSTI) and Qualified Source Testing Observer (QSTO) program is conducted by the Source Evaluation Society (SES) as a service to the source testing industry.


The goal of the SES QSTI/QSTO exam and abilities assessment is to determine whether the candidate demonstrates knowledge and the ability to apply source testing methods and fundamental engineering and chemistry principles in a manner consistent with that of a field test team leader. In addition to thorough and practical knowledge of source testing methods, those principles include an understanding of elementary physical gas laws and chemistry, basics of safety and hazardous material handling, and primary theories of source testing (e.g., isokinetic and proportional sampling). The candidate is expected to exemplify and demonstrate professional and ethical conduct not only during the exam process but also in representing SES as a QSTI or QSTO.


We believe that the SES QSTI/QSTO program is one way to satisfy the accreditation standard for organizations (e.g., ASTM D7036-04), and potentially new EPA regulations, as the SES QSTI/QSTO exams are designed to cover the areas of competence and basic methods described in the ASTM standard.


This program is consistent with the mission of SES to advance the applied sciences relating to source evaluation with respect to air pollution and air pollution control by: 

  1. promoting the development of concepts and techniques relating to the field;
  2. encouraging related professional development and knowledge;
  3. striving to ensure the highest professional standards for its members.


If you have any questions, please contact the SES QSTI/QSTO Program Committee Administrator at