Material Testing
Head of Department
Stephanie Knes
Head of Unit – Conformity Testing / Hygiene Inspections
Bernd Zeidler
Material Testing
Hygienic and technical regulations also define requirements for materials used in ventilation and air conditioning systems or evaporative cooling systems. For example, materials used in air-carrying sections must be corrosion-resistant or, in the case of plastics, must not be metabolizable by microorganisms. Whether plastic materials meet this requirement can be tested, for example, in accordance with DIN EN ISO 846, Methods A and C. If fungicides are used in the materials, their effectiveness can be assessed using Method B.
The chemical resistance of materials to various cleaning and disinfecting agents is also of relevance, as are cleaning tests to demonstrate that system surfaces can be cleaned and disinfected. In addition, the emission behavior of materials is of interest.
DIN EN ISO 846 “Determination of the effect of microorganisms on plastics”, Methods A, B and C
Method A is used to assess the inherent resistance of plastics to fungal attack in the absence of organic contamination.
Method B is suitable for testing the fungistatic or fungicidal effectiveness of a material.
Method C is used to assess the inherent resistance of plastics to bacterial attack in the absence of organic contamination.
For testing in accordance with DIN EN ISO 846 “Determination of the effect of microorganisms on plastics”, the test specimens are inoculated under defined conditions with test fungi for Method A and with a bacterium for Method C and incubated in a nutrient-free environment. After an incubation period of 4 weeks, microbial growth is visually assessed.
The following test fungi are used for Method A:
- Aspergillus niger
- Penicillium pinophillum
- Paecilomyces variotii
- Trichoderma virens
- Chaetomium globosum
The following bacterial strain is used for Method C:
- Pseudomonas aeruginosa
For the test, we require 4 test specimens per material with a surface area of 50 mm x 50 mm. For coatings or paint materials, glass or stainless steel plates should ideally be used as substrates.
Chemical resistance
In this test , specimens of the material to be tested are exposed to selected test substances under defined conditions with regard to exposure time, concentration, and test temperature, depending on the selected method, either by wetting or immersion. After the exposure period, the specimens are examined for visual changes such as peeling/abrasion, discoloration/change in gloss, blistering/swelling/softening, rust formation/corrosion, and cracking.
For this test, we require 14 specimens per material. These should have a minimum size of approximately 50 mm x 50 mm or a diameter of 50 mm.
The test conditions must be defined with the client prior to testing and should reflect the actual conditions of use.
Emission chamber measurements
Committee for Health-related Evaluation of Building Products.
For the tests, we require 2 specimens per material, each with a surface area of 100 mm x 100 mm.
Cleanability tests
To ensure long-term hygiene in ventilation and air conditioning systems, it is also necessary to verify cleanability and disinfectability. For this purpose, we offer various tests.
For this test, we require either one component or three specimens per material. The specimens should have a size of approximately 200 mm x 200 mm. In the case of systems consisting of multiple components, such as duct systems, a specific test setup is required, which is configured individually in consultation with the client.