Protective masks used multiple times by hospital personnel are safe

Investigation at TU Darmstadt: Sterilisation process at high temperature recommended

2020/04/29 by

FFP-2 respiratory masks worn by hospital personnel and the emergency services can be used multiple times without any concerns and continue to meet the strictest hygiene standards if they have been sterilised in advance for twenty minutes at 121°C. These are the findings of analyses carried out by TU Darmstadt for the Alice Hospital Darmstadt. The results should help to ease the supply shortages for FFP-2 masks.

Use of FFP-2 type respiratory masks at the Alice Hospital in Darmstadt.

On behalf of the Alice Hospital, the Centre for Structural Materials at TU Darmstadt investigated whether the twenty minute sterilisation process at 121°C that was recommended by the hospital for FFP-2 face masks had any negative impact on the function of the masks. The hospital did not believe that the recommendation published by the German Federal Ministry of Labour and Social Affairs of exposing the FFP-2 masks to dry heat at a temperature of 65-70° C to kill the SARS-CoV-2 virus was sufficient because the masks used in the hospital could also be contaminated by multiresistant germs or spores that can only be killed at much higher temperatures.

The Centre for Structural Materials set up electomicroscopic tests in its laboratories and also called on the assistance of the Institute of Reactive Flows and Diagnostics at TU Darmstadt for sample technical flow apparatus. The institute designed and validated special apparatus within a few days to test important properties of the masks such as particle filtering and any drop in pressure after multiple sterilisation processes. The detailed analyses of the material samples for new masks and also masks that had been sterilised multiple times at the Alice Hospital from different manufactures provided a clear picture: “We were not able to identify any negative impact with respect to a change or damage to the structure of the fibres or their filtering effect even after up to ten sterilisation treatments”, says Professor Matthias Oechsner, Head of the Centre for Structural Materials.

“We have achieved a high level of safety with the help of the work carried out at TU Darmstadt”, says Bernd Göckel, Manager of the Alice Sterile Supply Department. “We are now able to reliably evaluate the risk to employees and patients.” Alice Hospital now wants to carry out some accompanying microbiological tests related to the sterilisation of previously worn masks.

Centre for Construction Materials (State Material Testing Institute Darmstadt, Department and Institute of Materials Science): Prof. Dr.-Ing. Matthias Oechsner, Dr.-Ing. Holger Hoche, Heike Karpenstein, Meike Szabo

Institute of Reactive Flows and Diagnostics: Prof. Dr. habil. Andreas Dreizler, Florian Zentgraf, Pascal Johe, Johannes Emmert

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