ISO 9439 Ultimate Biodegradability Test for CO2 Evolution

    Introduction to  ISO 9439

    Testing of biodegradability is critical to understand the behaviour in the environment, in particular for water applications like wastewater treatment and natural environments step one. An ISO standardized test method based on OECD guidelines for measuring the aerobic degradability of chemicals is given by ISO 9439. Inhibition test for ready biodegradability, i.e., rapid and complete mineralization of the substance in the presence of air under standardised conditions. The result means regulatory, environmental, and product development compliance.

    Read more

    ISO 9439  Test Method

    Test procedure ISO 9439 CO2 evolution method uses respirometry to measure CO2 production during biodegradation and evaluate biodegradability over a 28-day exposure to a test substance. 
    Test sample concentrationIn this method, the concentration of 10 mg/l to 40 mg/l of organic carbon is mixed with the inoculum. 

    ISO 9439  Results and Interpretation

    As chemical decomposition occurs primarily via the formation of CO2 and H2O, measurements of CO2 produced during aeration and biodegradation can be used to indicate biodegradation of the test substance. During aeration of the working solution, it is important to use CO2-free air, which can be produced by using a few NaOH washing bottles to strip CO2 from the air. Once produced, CO2-free air can be used to aerate the working solution. While the solution is aerated, the test substance is biodegraded to form CO2.

    Read more

    The results are interpreted based on the percentage of organic carbon converted to CO2, with specific criteria for “readily” and “ultimate” biodegradability. 

    Alternatively, ISO 14593 and ISO 15462 are used for more accurate information on biodegradation rates. ISO 9439 is similar to OECD 301B and ASTM D5864.

    Use of ISO 9439  in Various Industries

    This test is primarily used by the environmental industry. 

    Materials Commonly Tested with ISO 9439 

     This test is suitable for highly soluble, poorly soluble (or even insoluble), and/or absorbing materials.

    Updated on September 17, 2026

    Divakar Shukla
    About Author
    Divakar Shukla
    Divakar Shukla is an Electrical and Electronics Engineer specializing in the convergence of embedded systems architecture, industrial automation, and applied artificial intelligence.
    Know More
    Testimonials
    Real results
    Engineers trust us with what matters most
    Why Choose Matestlab?
    Matestlab is a unified testing services partner based in the USA. Matestlab offers raw material and product testing services through accredited, expert laboratories primarily based in the USA. Matestlab supports physical, thermal, chemical, electrical, mechanical, environmental, and characterization testing needs through its global network of 2200+ accredited testing laboratories. Matestlab's in-house materials science experts curate and design comprehensive testing programs matched to the sample material and specific testing need, with regulatory requirements and confidentiality in mind.

    If you are looking for a managed and trusted testing partner to achieve your research goals, feel free to schedule a meeting with us or send us a request at connect@matestlabs.com to learn more about our services. For a quick quote, call us at (302)244-7710. We are happy to serve you.
    Start Your Testing
    Project Today
    Define your requirements and get access to
    specialized laboratories ready to deliver results
    Start Testing
    Contact us
    Partners with us
    Clients
    Vendors
    Process for testing
    • STEP 01

      You share your testing requirements

    • STEP 02

      You share your sample(s)

    • STEP 03

      We deliver your test reports

    Get your testing done

    Let us know your testing requirements and we will be right back with a solution.

      Let us root for each other. Collaborate to grow, expand, and accelerate our businesses.

      Partner with us