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Author: Mull, Birte ×

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  • Publication
    Quantitative distribution of SVOC substances in a room during and after cleaning measures
    ( 2019)
    Uhde, Erik
    ;
    Varol, Deniz
    ;
    Mull, Birte
    ;
    Salthammer, Tunga
    Semi-volatile organic compounds (SVOC) in the indoor environment are nowadays receiving increased attention. They can occur in a multitude of products and materials, and their release into air is governed by many parameters. Due to the fact that it is both time-consuming and analytically difficult to measure the usually very low concentrations of SVOC in the field, modelling the fate of these substances has become quite popular. Measured data, especially from realistic environments, is still very scarce. In this study, five different SVOC substances were introduced into two test rooms (one reference room, one intervention room). A wall paint (doped with 3 substances) and pre-cleaned house dust (doped with 2 SVOC substances) were used as sources. The indoor air concentrations of all five substances were monitored over a period of 180 days. After an equilibration phase of 80 days, interventions (air cleaning, vacuum cleaning) were performed in one of the rooms, and the effect on air concentrations was monitored. The interventions included short-term operation of an air purifier and continuous operation over 50 hours. During operation of the air purifier, the air concentration of the target substances in the room was found to be reduced by approximately 50%. Following deactivation of the purifier, however, the concentration swiftly returned to its initial value. This is a strong indication of an evaporation controlled process. The effect of vacuum cleaning on air concentrations was negligible, and even the successive removal of the doped dust in the intervention room during the experiment did not result in a significant decrease of the SVOC concentration compared to the reference room.
  • Publication
    Distribution of five SVOCs in a model room
    ( 2019)
    Uhde, Erik
    ;
    Varol, Deniz
    ;
    Mull, Birte
    ;
    Salthammer, Tunga
    With regard to the application of semi-volatile organic compounds (SVOCs) in products for indoor use, a distinct trend towards substitutions can currently be observed. Among the possible phthalate alternatives, in particular the adipic acid esters have gained in market importance. The chemical-physical and thermodynamic properties of the phthalates and adipates allow the conclusion to be drawn that they are distributed between different compartments (gas phase, particle phase, dust, material surfaces) of the indoor space. There are, however, hardly any data in existence which were collected in a real environment over six months and longer. Diisobutyl adipate (DiBA), di-n-butyl adipate (DnBA), dipentyl phthalate (DPP), butyl benzyl phthalate (BBzP) and di-2-ethylhexyl adipate (DEHA) were selected as model substances. By means of spiked latex paint and spiked house dust, these SVOCs were introduced into two identically equipped test rooms. One room was cleaned regularly, whilst the reference room was not entered for a 133 day experimental period. The concentrations of the five target substances were determined in the air and in material samples (carpet, vacuum-cleaner bags, filters). During the operation of an air purifier, the air concentration of the target substances in a room could be reduced by more than 50%. In the reference room, a correlation between the logarithmic air concentration and the reciprocal room temperature was found. The results show with great clarity the complexity of the conditions in an indoor room. Models can therefore depict the exposure as a statistical average but not, however, describe the individual case.
  • Publication
    Reproducibly emitting reference material on thermoplastic polyurethane basis for quality assurance/quality control of emission test chamber measurements
    ( 2017)
    Richter, Matthias
    ;
    Mull, Birte
    ;
    Horn, Wolfgang
    ;
    Brödner, Doris
    ;
    Mölders, Nils
    ;
    Renner, Manfred
    Volatile Organic Compounds (VOC) are ubiquitous in the indoor air since they are emitted from materials used indoors. Investigations of these materials are mostly carried out in emission test chambers under controlled climatic conditions. Reference materials are an important tool for quality assurance/quality control of emission test chamber measurements but so far they are not commercially available. In this study, a new approach was tested to develop an appropriate reference material with homogenous and reproducible emission of the VOC with well measurable air concentrations in emission test chambers larger than 20 L at air change rates of 0.5-1 h−1. Thermoplastic Polyurethane (TPU) was selected as matrix material which was impregnated with 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (texanol) as test VOC using compressed carbon dioxide. An optimization of the impregnation parameters such as temperature, pressure, time, VOC injection volume and TPU sample size was performed until the targeted area specific emission rate (SERa) value was reached. Further aspects like process control, storage effects and correlation of the sample size to the emission rate were investigated. It was found that the SERa immediately after sample preparation were not reproducible between the batches but became unified 10 days after loading into the test chamber indicating the necessity of aging before use. SERa between 13,000 and 18,000 mg m−2 h−1 were obtained, and the impregnated materials could be well stored in aluminum-coated polyethylene foil for at least seven weeks without significant losses. Furthermore, the impregnation of styrene and the SVOC 2,6-diisopropylnaphthalene was tested.