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Biomedical subjects

E Thofern

Publications and source records attributed to E Thofern.

50 records · Page 3Linked to original sources
PubMed1975

[Glass fibre HEPA filters. II. Communication: Microbiological and physico-chemical researchs on used and unusued, hydrophilic and hydrophobic filter materials in an air conditioning plant (author's transl)].

Hydrophobic and hydrophilic, used and unused HEPA filters from various manufacturers, inoculated with vegetative bacteria, bacterial and fungal spores, were exposed to clean outside air for up to 17 weeks in an air conditioning plant. With relative humidities up to 60%, an increase in germ count could not be found. The rate of killing the micro-organisms inoculated were different and were generally higher on used filters. The low water content of the filter material was apparently not sufficient for microbial growth. In addition, the increase in electric conductivity and reduction of pH value resulting from deposition of substances from the outside air with an acid reaction ascertained in the aqueous filter extracts had a negative effect on the living conditions of the microorganisms.

Air Conditioning↗
PubMed1975

[Glass fibre HEPA filters. I. Communication: Microbiological and physico-chemical researchs on used and unused, hydrophobic and hydrophilic filter materials at relative humidities up to 98% in the climatic test chamber (author's transl)].

1. At high humidities up to 98%, an increase in bacteria cannot be detected. This applies to all HEPA filters investigated from the various manufacturers, independent of whether they are hydrophilic or hydrophobic, used or unused. 2. Fungal growth can only be obtained when large amounts of nutrient material (e.g. bacterial cultures) are present. In these cases a streaky growth appears . Under normal conditions of use, however, such intense contamination is not to be expected because of the prefiltration. Penetration only occurs with fungi. 3. Limitation of supply air humidity to 90% or less seems therefore to be unjustified on the basis of these investigations, if prefiltration and a satisfactory intermixing section can be guaranteed technically, and condensation is avoided. 4. HEPA filters of Grade S from various manufacturers and with different behaviour with respect to water do not allow bacterial growth even in the presence of nutrients. Additional measures for the killing of bacteria are therefore not considered necessary.

Air Conditioning↗
PubMed1975

[The behavier of Pseudomonas aeruginosa in surface water, cooling water and waste water (author's transl)].

This is a report on the occurrence and numerical behaviour of Ps. aeruginosa in natural waters with and without waste water contamination, in dams, cooling water circulations and cooling water discharge, in clarification plant and supplementary laboratory tests. The results show that Ps. aeruginosa may occur in the natural flora of open waters, but only following the introduction of human sewage. In the main, a more or less rapid reduction in the number of Ps. aeruginosa to low levels occurs, but periods of several days to several weeks must be allowed for this. In the presence of large quantities of nutrient, multiplication of Ps. aeruginosa in natural waters cannot be excluded. It certainly appears in technical systems such as cooling water circuits and filter plants. Presumably Ps. aeruginosa also multiplies in waste water, whereas in the biological aerobic clarification process a reduction occurs. The effect of a higher temperature on the survival or multiplication of Ps. aeruginosa could not be confirmed by laboratory experiments.

Cell Count↗