BS EN ISO 846:2019 pdf free.Plastics – Evaluation of the action of microorganisms.
The test involves exposing test specimens of plastic to the action of selected test strains of fungi and bacteria (or, in the case of the soil-burial test, to microbially active soil) for specified or agreed periods of time under specified conditions of temperature and humidity.
At the end of the exposure, the test specimens are assessed before and/or after cleaning by visual examination and/or any change in mass or other physical properties is determined.
The results obtained with the specimens exposed to microorganisms (test series I) are compared with those obtained from retained reference specimens (test series 0) or sterile specimens (test series S) kept under the same conditions.
In the case of testing fungistatic properties, a visual assessment is made between test specimens free of biocides and with those containing biocides to demonstrate the effect of a biocide in a qualitative manner.
Short descriptions of the test methods used to determine the resistance of plastics to fungi (method A)
or the fungistatic effects (method B), resistance to bacteria (method C) and resistance to soil
microorganisms (method D) are given in 4.2 to £4.Test specimens are exposed to a mixed suspension of fungal spores in the presence of a humidity 95 % relative humidity. After the limited nutrients from the spore itself are depleted through formation of a germination tube, the fungi can only grow at the expense of the material of the test specimens. If the specimens contain no nutritive component, the fungi cannot develop mycelia and there will be no deterioration of the plastic.Any inhibition of growth either on the plastic or in the nutrient-agar medium (zone of inhibition) shows fungistatic activity of the plastic or the presence of a fungicidal treatment. In order to show a basic qualitative effect of a biocide in a plastic material, specimens free from biocide
shall be included in the test. Only if these biocide-free specimens show more growth than the specimens containing biocides can a qualitative indication of fungistatic or fungicidal efficacy be determined.BS EN ISO 846 pdf download.