How do I effectively control inactivation processes in autoclaves?
Dr. Tino Köster
The Committee for Biological Agents (ABAS) publishes a technical recommendation on the process validation of waste inactivation processes in autoclaves.
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Both the Genetic Engineering Safety Ordinance (GenTSV) and the Biological Agents Ordinance (BioStoffV) require waste to be treated, depending on the hazard potential, before final disposal, preferably by means of physical inactivation process According to the GenTSV, these requirements are usually met by the thermal inactivation at 121 °C or 134 °C for 20 minutes This becomes problematic when it comes to the inactivation of microorganisms in heterogeneous laboratory waste (e.g., centrifuge tubes or syringes) or special matrices (e.g., carcasses). For this purpose, the autoclave programs must be adapted and optimized, and the inactivation processes must be validated using thermoelectric detection or bioindicators.
According to ABAS, non-infectious "worst-case loads" should be used for process validation to test whether the above-mentioned requirements for successful inactivation reach difficult levels. Packaging should not impede vapor penetration, and mixed loads of solid and liquid waste should be avoided. If autoclaving closed containers is unavoidable, it must be ensured that the inactivation temperature is reached within these. ABAS also recommends conducting thermoelectric validation at at least six measuring points in autoclaves with a chamber volume of less than 800 l and at at least ten measuring points in those with a chamber volume of more than 800 l. To be able to demonstrate the necessary holding time, the process parameters must be recorded and documented.
When inactivating liquid waste The "worst-case loading" must simulate the maximum number of the largest individual liquid quantities, and the measurement must be taken in the center of the respective containers. To enable a direct comparison between the autoclave and, for example, the data logger, the reference container should also be prepared with a thermal sensor. In all cases, the container material with the poorest thermal conductivity (e.g., plastic) should be used as the reference.
At the Inactivation of solids It must be ensured that air inclusions are removed by the fractional pre-vacuum process and that the measuring devices or bioindicators are placed at critical points in the center of the load.
For both liquid and solid waste, the Detection of the inactivation temperature in three replicates be reproducible. Revalidation is recommended regularly and is necessary if the load changes or if procedural changes are made to the autoclave.
The ABAS technical recommendation can be found here .