SES Qualified Source Test Individual and Observer (QSTI /QSTO) Program

The Source Evaluation Society QSTI/QSTO Committee has developed general requirements for applicants for the SES QSTI/QSTO approval. The SES will issue approval documents to qualified applicants in the following methods groups:  

  • Group 1 - Manual Gas Volume and Flow Measurements and Isokinetic Particulate Sampling Methods
  • Group 1a - Stack Gas Flow Rate Measurements Sampling Method
  • Group 2 - Manual Gaseous Pollutants Source Sampling Methods
  • Group 3 - Gaseous Pollutants Source Sampling Methods
  • Group 4 - Hazardous Metals Measurement Methods
  • Group 5 Part 75 CEMS RATA Testing


To apply for initial QSTI or QSTO approval, you must meet the following requirments:  

  • 1. Have at least 1 year of experience in the area selected for testing, or have completed or observed 10 field tests using test methods in the relevant methods group.
  • 2. Pass one or more methods group exam. (Two-hour exam) (Click ETA registration to access the ETA web site and the register for a paper exam.) (Click Scantron/Castle Worldwide registration to access the Scantron/Castle Worldwide website and register for an online exam. Once registration for an exam has occurred, the exam must be taken within 6 months.)​
    •  In Scantron's efforts to be collaborative and supportive to their clients and candidates, Scantron is modifying their testing policies to allow additional flexibility to those who need it. If you have a scheduled testing appointment between May 1 and June 30, 2020 and decide to reschedule that appointment, Scantron will waive the rescheduling fee.
  • 3. Submit a completed and notarized application for approval. You must have a wet ink signature on your application. You must also submit descriptions of at least two different field testing projects in which you participated. (Click SES QSTI/QSTO Approval Application and Renewal Policies and Procedures for more details on the application and renewal procedures). (Select the appropriate QSTI or QSTO application form listed below.)
  • 4. Submit at least three recommendations. At least two of the recommendations must be from people outside your current place of employment. (Click QSTI Reference Form to link to an approved recommendation form).

You should direct applications and associated information for SES QSTI or QSTO approval and any questions about these requirements or for information about the program to the SES QSTI/QSTO Administrator by email to the SES QSTI/QSTO Administrator, Theresa Lowe at

Note also the ECMPS AETB reporting requirements includes a provision for an email address be noted for the exam provider. This address is


  • The SES will maintain confidentiality for all application information and share such information only as necessary with no one but the SES QSTI/QSTO Committee. The SES QSTI/QSTO administrator will review and advise you if you should provide any additional information to complete your application. The Committee meets monthly to review applications, and SES posts the date of the next Committee meeting on the SES website. (Select SES Home page for the date of the next SES QSTI/QSTO application review meeting.) The deadline to submit your application and ensure that the committee acts on it at the committee’s next meeting is three days prior to the date of the scheduled meeting.

  • If you have any questions, please contact Theresa Lowe.

  • Thank you,
Theresa Lowe
SES QSTI/QSTO Program Administrator





  • Tips for Passing the Exams/Study Guidelines


  • RFT (viewable in any word processor)
  • PDF

QSTI Program Complaint/Suspension Guidelines

Frequently Asked Questions

List of Qualified Stack Testing Individuals/Qualified Stack Testing Observers