Oklahoma DEQ Laboratory Accreditation
Oklahoma environmental lab accreditation, state rules and the TNI track.
How the Oklahoma DEQ accredits environmental labs under two rule chapters, how out-of-state labs qualify, what is changing, and the calibration rules in the code.
At a glance
How environmental lab accreditation works in Oklahoma.
Oklahoma is a NELAP state. The Department of Environmental Quality accredits labs under two separate rule chapters: a state accreditation track in OAC 252:301 and a TNI track in OAC 252:307.
NELAP accreditation body
- Program
- Laboratory Accreditation Program (LAP), State Environmental Laboratory Services, Oklahoma Department of Environmental Quality
- NELAP status
- Listed by TNI as a NELAP accreditation body as of October 2026. DEQ accredits to the TNI standard under OAC 252:307.
- State track
- OAC 252:301 applies to all labs certified or applying to be accredited by DEQ under that chapter, in the Drinking Water, General Water Quality and Petroleum Hydrocarbons matrices.
- TNI track
- OAC 252:307 applies to any environmental lab that seeks accreditation under it and incorporates by reference Volume 1, Modules 1 through 7, of the TNI Environmental Laboratory Sector standard as adopted January 31, 2020.
- Who needs it
- DEQ states that several state rules require the use of a state-accredited lab. OAC 252:301-1-2 lets an unaccredited lab submit operational testing for municipal wastewater and water supply systems when a DEQ-certified laboratory operator ran the lab and signs the report.
- Field labs
- Field laboratories have a separate rule, OAC 252:302, Field Laboratory Accreditation.
- Out-of-state labs
- Under OAC 252:307-11-1, DEQ grants accreditation to labs accredited by another TNI primary accreditation body, for the fields they hold. Under OAC 252:301-5-4, out-of-state labs already in the program may be required to have an on-site evaluation by a DEQ approved assessor.
The accreditation cycle
From application to renewal.
The steps below summarize OAC 252:301 and 252:307 as DEQ currently posts them. DEQ has proposed changes to the accreditation year and renewal deadlines, so confirm current dates with the Laboratory Accreditation Program.
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Choose the track and scope
Apply under OAC 252:301 by matrix (Drinking Water, General Water Quality, Petroleum Hydrocarbons) or under OAC 252:307 by field of accreditation to the TNI standard.
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On-site evaluation
Both chapters require an on-site evaluation before initial primary accreditation. Under OAC 252:301-5-4, DEQ may evaluate a lab approximately biennially, or upon complaint; DEQ has proposed approximately every three years.
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Proficiency testing
Two PT studies per year, approximately six months apart. Labs must pass two of the most recent three studies attempted (252:301-7-5 and 252:307-9-3).
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Annual renewal
Accreditation is renewed annually. As posted, OAC 252:307-1-6 sets a September 1 to August 31 term and DEQ’s 2025 fact sheet says scopes expire August 31, but DEQ has proposed a January through December period.
Initial calibration
What auditors check in your initial calibrations.
Oklahoma’s state track writes its own default calibration frequencies into OAC 252:301, while the TNI track incorporates the TNI standard. Under Chapter 301, those defaults apply where the approved method does not set its own QA/QC requirements.
A range that brackets what you report
The lowest standard should sit at or below your reporting limit and the highest at or above the top concentration you report. Results outside the calibrated range need to be qualified.
Error at the low end, not r² alone
A correlation coefficient of 0.999 can still hide a low standard that back-calculates 30 percent off. Auditors look at relative error, especially at the lowest levels.
Records that rebuild the curve
Raw responses, the model and weighting used, any excluded points with the reason, and the verification that followed. An auditor should be able to reconstruct every initial calibration from the record.
Three standards and a check every ten samples
Where approved methods do not specify minimum QA/QC requirements, OAC 252:301-9-54 and 9-55 require a minimum of three concentrations of standards for daily calibration plus one continuing calibration check standard after each ten samples. For inorganics, if a check is outside plus/minus 10 percent, the lab should repeat samples tested after the last acceptable check.
Source: OAC 252:301-9-54 and 252:301-9-55
OAC 252:301-9-56 also requires calibration records to include the calibration curve or the coefficient of the linear equation that describes it, and the percent recovery of an initial calibration check standard.
Self-check
Are your initial calibrations ready for an Oklahoma assessment?
Tick what your lab could show an auditor today. Nothing you select is saved or sent anywhere.
6Checks to work through
Select each item your lab could show an auditor today.
A self-assessment to help you prepare, not a compliance determination.
Oklahoma specifics
One agency, two rule chapters, and rules in revision.
Oklahoma DEQ is both the state’s accreditation program and a NELAP-recognized accreditation body. A lab can be accredited under OAC 252:301, the state’s own chapter covering drinking water, general water quality and petroleum hydrocarbon analyses, or under OAC 252:307, which incorporates the TNI standard. Drinking water accreditation is available under both chapters, and OAC 252:307 notes that TNI accreditation may be required for labs reporting drinking water analyses to DEQ.
Chapter 301 is specific about calibration. Where the approved method does not set its own QA/QC requirements, it requires at least three standard concentrations for daily calibration and a continuing calibration check after every ten samples, with a plus/minus 10 percent limit for inorganic checks. It also requires a written QA plan implemented as a QA/QC program, and annual calibration or verification of support equipment.
The rules are changing. DEQ’s 2025 rule impact statements for Chapters 301 and 307 propose a January through December accreditation period, a September 15 deadline for renewal documentation and a December 15 deadline for renewal invoices, and the Chapter 301 proposal moves routine assessments to approximately every three years. These rulemakings, with Chapter 302, were on the Environmental Quality Board agenda for January 21, 2026. As of October 2026, the rule text DEQ posts still shows 2022 as its latest amendment, so confirm current deadlines with the program.
How WLTR helps
Calibration evidence ready for an Oklahoma assessment.
WLTR independently reviews the calibration your instrument software produced. Your analyst still makes the final call. What changes is that the evidence is complete, consistent across analysts, and ready before the auditor asks for it.
- Each analyte reviewed one at a time in the instrument software.
- The model and weighting are whatever the batch was processed with.
- r² is the number most people look at, even though it does not measure error at the low end.
- QA signs off without an independent check on the curve.
- Every analyte and every candidate model side by side in the Calibration Intelligence dashboard.
- Diagnostics run automatically and the best fit curve is identified, with the reasons recorded.
- Relative error at every level, including the lowest standard, shown on one screen.
- A traceable record your QA manager can review, sign and hand to an Oklahoma DEQ assessor.
See how your own ICAL data looks when every analyte and model is laid out for review.
Questions
Oklahoma accreditation FAQs
Is Oklahoma a NELAP state?
Yes. TNI lists the Oklahoma Department of Environmental Quality as a NELAP accreditation body as of October 2026. DEQ accredits to the TNI standard under OAC 252:307 and also runs a state accreditation track under OAC 252:301.
What is the difference between OAC 252:301 and 252:307?
OAC 252:301 is Oklahoma’s own accreditation chapter, organized by matrix (Drinking Water, General Water Quality and Petroleum Hydrocarbons) with its own PT and QA/QC rules. OAC 252:307 accredits to Volume 1 of the TNI Environmental Laboratory Sector standard, which it incorporates by reference.
Who accredits drinking water labs in Oklahoma?
The Oklahoma DEQ Laboratory Accreditation Program. Drinking Water is a matrix under OAC 252:301, and OAC 252:307 offers drinking water categories including metals, general chemistry, microbiology, asbestos, SOCs, VOCs and radionuclides.
Can an out-of-state lab be accredited in Oklahoma?
Yes. Under OAC 252:307-11-1, DEQ grants accreditation to labs accredited by another TNI primary accreditation body, for the fields they hold. Under OAC 252:301, an out-of-state lab already in the program may be required to have an on-site evaluation by a DEQ approved assessor.
Does Oklahoma have its own calibration rule?
Yes, for the state track. Where approved methods do not specify minimum QA/QC requirements, OAC 252:301-9-54 and 9-55 require at least three standard concentrations for daily calibration and a continuing calibration check after every ten samples.
Sources
Primary sources for this page.
- TNI, NELAP accreditation bodies (opens in a new tab)
- Oklahoma DEQ, Laboratory Accreditation Program (opens in a new tab)
- Oklahoma DEQ, laboratory accreditation program resources (opens in a new tab)
- OAC 252:301, Laboratory Accreditation (DEQ copy) (opens in a new tab)
- OAC 252:307, TNI Laboratory Accreditation (DEQ copy) (opens in a new tab)
- Oklahoma DEQ, Selecting an Accredited Laboratory fact sheet (opens in a new tab)
- Oklahoma DEQ, OAC 252:301 rule impact statement (2025) (opens in a new tab)
- OAC 252:301-9-54, inorganic chemistry (Justia, secondary copy) (opens in a new tab)
This page summarizes public program information to help labs prepare. Requirements change, and the agency’s current rules and guidance always take precedence. WLTR is not affiliated with or endorsed by the Oklahoma Department of Environmental Quality. Spot something out of date? Tell us at admin@wltr.tech.
Before your next assessment
See your Oklahoma ICALs the way an assessor will.
Bring a recent initial calibration. We will walk you through every analyte and candidate model in the Calibration Intelligence dashboard, the best fit, and the record your QA manager would sign.
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