This article discusses several research-based observations on biodegradability testing of chemical wastes, referring guidelines provided by the Organisation for Economic Cooperation and Development (OECD). Several authors have advocated a multi-tiered approach to biodegradability testing, based largely on the practicality of investigating what may be a many factored problem of persistence, and the resultant high costs. The OECD, reportedly, has taken a lead through its Environmental Directorate in establishing standard methods which form the basis of the regulatory tests currently required in many countries for product registration. The OECD define three levels of tests, namely the "Ready," "Inherent," and "Simulation" biodegradation tests. The method described by researcher R.N. Sturm, which is the basis of the OECD 301B, is claimed to be the only current test protocol making a direct measure of a product of biodegradation through carbon dioxide evolution test methods. The method involves the use of a steady carbon dioxide-free air supply to drive carbon dioxide from the test medium to bubble impingers containing barium hydroxide as a carbon dioxide absorbent.