Things to Look for from Your NELAP Accredited Laboratory

Jun 7, 2019

In 1995, the Environmental Protection Agency (EPA) established the National Environmental Laboratory Accreditation Program (NELAP) to address a problem with numerous environmental laboratory accreditation program inefficiencies and inconsistencies. Today, The NELAC Institute (TNI) is comprised of several core programs for accrediting environmental projects.

What Is NELAP Accreditation?

NELAP was established to provide a better way to develop consensus on national standards for environmental laboratory accreditation. The NELAP system includes federal, state and local agencies, as well as the laboratories and environmental interest groups. These groups participate in committees and meetings to provide continual guidance to TNI.

In addition to the NELAP committees, a federal advisory board committee provides public sector feedback. Quality assurance audits are provided through agency representatives or through third party auditors to ensure that the laboratory is complying with the NELAP standards for any required procedure. Third-party auditing of NELAP accredited laboratories is required at regular intervals - usually every two years - for accreditation continuance.

Why Is NELAP Accreditation Beneficial?

While it is generally true that as the years have passed, the sensitivity, precision, and accuracy of environmental testing data have generally improved, there is a growing perception among the data user community that legally defensible data is frequently not being provided by laboratories. This situation can only be remedied by a NELAP accreditationfundamental change in how laboratories face their responsibilities to the community at large.

NELAP accreditation provides the environmental testing industry with internationally accepted requirement on the elements of a comprehensive ethics program, best practices for analysis and quality assurance. All this together provides the end data user with accurate, precise, legally defensible data in a framework that strives for great customer service and constant improvement.

Things to Look For

When looking at a NELAP accredited lab, the focus should go beyond the certificate to how they go above and beyond the minimum standards. The standard has a section on "Service to the Client" which allows the client to view quality system documentation. Some examples of documents worth reviewing are: Quality Assurance Manual (QAM), their written Standard Operating Procedures (SOPs), and any applicable demonstration of capability (DOC) along with backup information. These will give you an idea of their analysis policies, how they treat samples, and how they ensure a competent person is performing the requested analysis. 

Any potential laboratory should also be able to supply an example lab report. The easiest example laboratory report for them to supply would be an analysis of their latest Proficiency Test (PT) samples. NELAP requires accredited laboratories to purchase, analyze and generate a lab report on third-party blind PT samples at least twice a year. This example report should also be supplied with a pass/fail grade from the PT supplier When reviewing the information provided, pay close attention to the following areas:

Instrument Calibrations

- Look at the date of analysis for the calibrations compared to the field samples.

- Make sure calibration requirements for your required test methods are being met.

NELAP requires a full 5 point instrument calibration along with a least-squares regression when a significant change is made to either the instrument or the operator. A continuing calibration standard is analyzed at least daily to assure the original instrument calibration is still within specifications. Because of this, some laboratories will only calibrate the instrument on an annual basis. Some EPA methods require more, for example:

  • EPA 26/A: Requires a full pre and post test calibration (EPA 26A: 10.2.3) along with averaged duplicate injections (EPA 26A: 11.1.3).

CTM 027: Requires a 6 point calibration be used (EPA CTM-027: 4.2.2)

Detection Limits

  • - Check if their Method Detection Limit (MDL) is based on collected data or assumption?

- Look to see if they use an established method to calculate the MDL?

 NELAP requires an MDL for most instrument based methods (including Ion Chromatography) but excludes others, such as particulate weight per Method 5. Some labs will make assumptions based on optimal instrument handling, while others will go the extra mile to make a defensible MDL per an established recognized method, such as 40 CFR 136 Appendix B.

Sample Analysis

  • - Make sure sample analysis requirements for your required test methods are being met.

  • - See that all data that may be altered by the user such as a chromatogram is available in its original form for review.

Usually found on the DOC or an example report you can see the analysis standards upon which their procedure is based. If it's not the analysis method you ran in the field, data should be analyzed further. There are some EPA methods that have requirements above and beyond the normal analysis:

  • EPA 18: A spike-recovery is part of the method-required sampling/analysis technique validation. Any technique that passes the criteria is allowed. Inquire with your vendor as to their spike-recovery technique. You’ll especially need this information if planning on using the adsorption tube sampling technique.

  • EPA 26/A: All analysis in duplicate injections (EPA 26A: 11.1.3)


Most labs offer several NELAP accredited analyses. Contact us today to discuss accreditation and your testing needs!