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The development of low volatile organic compound emission houses

Guo, Hai (1999) The development of low volatile organic compound emission houses. PhD thesis, Murdoch University.

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Indoor air pollution by a variety of volatile organic compounds (VOCs) has become increasingly recognised as a public health problem. Although much work has been done in Scandinavian countries and the United States, very limited studies on the emissions of total VOCs from indoor materials have been reported in countries with Mediterranean climates, or warm temperate climates where the weather conditions and house ventilation rate are quite different from those in which most studies have been reported. There is also a lack of information about specific materials suitable for buildings for which the main priority is healthy indoor air. Therefore, the primary purposes of this project were to characterise VOCs emissions from building materials and consumer products and to develop a model for a low VOC emission house.

Environmental test chambers with controlled temperature, relative humidity and air exchange rate were developed to evaluate emissions of total volatile organic compounds (TVOCs) from a variety of building and furnishing materials and consumer products. Organic vapours were collected on Tenax - GR and quantified by GC/FID with thermal desorption techniques. Headspace analysis was used to assess VOCs emitted from indoor pollution sources. The main VOCs were detected by GC/MS techniques. A case study involving the design and development of a low VOCs emission house and testing of this house is presented. This low VOCs emission house emphasises pollution prevention based on the results of environmental chamber testing and headspace analysis.

The findings in this study support the hypothesis that indoor materials make significant contributions to the levels of TVOCs in indoor air in houses. This study supports the hypothesis that TVOCs concentrations in indoor air in the houses tested were much lower than those reported in most studies. The findings from this research support the hypothesis that the indoor air quality model is adequate to estimate the TVOCs concentrations in indoor air.

Measurements of VOCs emissions from 15 paints, 3 adhesives, 3 furniture polishes, 11 carpets, 6 pressed wood products and 10 consumer products in environmental chambers by GC/FID showed that the indoor materials tested all emitted a variety of VOCs. “Wet” sources such as paints, adhesives, furniture polishes and consumer products, showed a rapid change in initial emission characteristics. These “wet” sources initially have high TVOCs emissions and the concentrations of TVOCs emitted from these materials decreased significantly over time. Most of these “wet” sources emit aromatic hydrocarbons e.g. benzene, toluene, xylene isomers, styrene, ethylbenzene, which are suspected to be carcinogens.

“Dry” sources such as carpets and pressed wood products have emission characteristics which change relatively slowly with time. Compared with “wet” sources, these “dry” sources have low TVOCs emissions both in number and amounts of VOCs.

Double-exponential empirical models were used to describe the time dependence of TVOCs concentrations and emission rates in environmental chambers. The correlations between measurements of indoor materials in environmental chambers and the predictions of the model showed that the change of TVOCs concentrations for a variety of indoor materials in environmental chambers fitted the double-exponential model very well. The models enabled the characterisation of complex TVOCs emissions and their time dependence with relatively few parameters. With this double-exponential model, the mechanism of TVOCs emissions from indoor materials and products can be characterised. The model also enabled the calculation of a variety of emission parameters which can be used to predict indoor air quality.

This study measured TVOCs concentrations in one new conventional house and one low VOCs emission house. The TVOCs concentrations in the conventional house ranged from 60 - 162 Jig/nr and the TVOCs levels in the low VOCs emission house ranged from below the limits of detection (1 jig/m3) to 43 pg/m3. These values are much lower than the published data (0.48-31.7 mg/m3) for new houses. They are even lower than published data for mixed new and old houses (0.19-9.4 mg/m3). This is due to the high air exchange rates in these houses in warm climates, which make maximum use of sea breezes to minimise the accumulation of indoor air pollutants; and the use of low TVOCs emission materials in the low VOCs emission house.

An indoor air quality model was used to predict the indoor air quality in these houses. This study preliminarily validates the indoor air quality model by comparing the model predictions with the measured data. This model considered the effects of air exchange rate, source strength and source size on the TVOCs concentration indoors. The correlations (R2 = 0.90, ProbN = 0 - 0.6%) between measurements of indoor TVOCs concentrations in the conventional house (chapter 11) and the predictions of the model showed that the indoor air quality model provided useful predictions of the change of TVOCs concentrations in the conventional house. With this indoor air quality model, the TVOCs concentrations in indoor air under specific conditions (specific ventilation rates and material loadings) can be predicted.

This study measured TVOCs rather than individual VOCs concentrations from indoor materials. The next step in research should be aimed at investigating individual VOCs emissions and their effects on indoor air quality and human health. This would extend the existing database to describe and predict emissions of VOCs from indoor materials. It would also provide a better understanding of population indoor exposure.

Item Type: Thesis (PhD)
Murdoch Affiliation: Division of Science and Engineering
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Murray, Frank
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