Test aerosols

Test aerosols and methods for testing the effectiveness of air purification technologies against Sars-CoV-2

HHN team

Project partners

Prof. Dr. Susanne Bailer, Universität Stuttgart

Prof. Dr. Achim Dittler, Karlsruher Institut für Technologie

Prof. Dr. Gunnar Grün, Universität Stuttgart

Prof. Dr. Thomas Iftner, Universitätsklinikum Tübingen

Prof. Dr. Jennifer Niessner, Hochschule Heilbronn

Prof. Dr. Michael Schindler, Universitätsklinikum Tübingen

Prof. Dr. Konstantinos Stergiaropoulos, Universität Stuttgart

Prof. Dr. Zöllner, Hochschule Heilbronn

Brief description and objective

The corona pandemic continues to restrict public life and has far-reaching long-term effects on German society, culture, science, and the economy.

In particular, the spread of the corona virus indoors and via airborne particles, i.e. aerosols, is currently at the center of many discussions and is determining for many measures - from the operation of schools and kindergartens, hygiene in hospitals and medical practices, in offices, administrative and production facilities through to the hotel, restaurant and event industry.

In order to master the possible risk of infection via highly pathogenic aerosol-borne viral pathogens (SARS-CoV-2, influenza etc.), air purification and inactivation technologies are hotly debated and more and more promising devices are coming onto the market. In the absence of established test and evaluation procedures, however, no statements can currently be made about the effectiveness and comparability of such devices for inactivating SARS-CoV-2 and other aerosol-borne pathogens, so that an evidence-based assessment is not possible.

This lack of procedures begins with the selection of suitable test aerosols depending on the technology to be tested, their application, characterization and sampling, the selection and comparability of surrogate viruses with regard to the original pathogen and extends to the definition of suitable test arrangements and procedures to the necessary ones accompanying investigations, such as the proof of by-products or the sound power.

Project goals

  1. Definition of test aerosols, their application, characterization, and sampling
  2. Proof of effectiveness of methods for inactivating SARS-CoV-2 in aerosols by determining the infectivity in cell culture
  3. Proof and limitation of the admissibility of the conclusion by analogy of particles and corona surrogate viruses compared to realistic aerosols with SARS-CoV-2 exposure
  4. Determination of the parameters of the devices and rooms influencing the proof of effectiveness
  5. Definition of test procedures and accompanying evidence


Measurement and simulation of indoor aerosol particle transport

Thermal dummies with PM1 particle sensors (left) and simulation of aerosol particle transport with an infected dummy and an air purifier (right). Simulatin: Adrian Tobisch, HHN.

Schematic representation of HHN’s test bench for investigating the inactivation of SARS-CoV-2 in aerosols by UV-C radiation

  • Aerosol generator: Generation of SARS-CoV-2 loaded aerosols
  • UV-C permeable quartz glass construction: Controlled exposure of the aerosol particles with UV-C radiation of known intensity
  • Sampling filter: Here the aerosol particles are collected and tested for active and inactive viruses in the virology department
  • HEPA filter: Highly separating filter as an additional safety measure
  • Vacuum pump: This device sucks the particle-laden air through the test bench


In addition, radiation intensity, temperature, and ozone concentration are measured.

The project is funded by the Ministry of Science, Research and the Arts (Ministerium für Wissenschaft, Forschung und Kunst (MWK) Baden-Württemberg.

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