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• Unflued gas appliances and air quality in Australian homes (PDF - 720 KB)
• Unflued gas appliances and air quality in Australian homes - Appendix 1 (PDF - 15 KB)
• Unflued gas appliances and air quality in Australian homes - Appendix 2 (PDF - 12 KB)
• Unflued gas appliances and air quality in Australian homes - Appendix 3 (PDF - 686 KB)
• Unflued gas appliances and air quality in Australian homes - Appendix 4 (PDF - 295 KB)
• Unflued gas appliances and air quality in Australian homes - Appendix 5 (PDF - 943 KB)
• Unflued gas appliances and air quality in Australian homes - Appendix 6 (PDF - 57 KB)

About this report

The Department of the Environment and Heritage (DEH ) Unflued Gas Appliances and Air Quality in Australian Homes (UGA) Study evaluated the exposure of occupants in residential properties where unflued gas heaters were in operation, to a range of atmospheric contaminants in temperate and cold climates.

In summary, study objectives were achieved through measurements and observations in 116 suburban houses (148 house-days) in Sydney, Melbourne, country Victoria and Canberra.

Parameters measured or recorded included:

• Indoor concentrations of nitrogen dioxide, nitric oxide, carbon monoxide, carbon dioxide and formaldehyde;
• Outdoor concentrations of nitrogen dioxide and nitric oxide;
• Indoor temperature and relative humidity;
• Ventilation rate;
• Ambient wind speed, wind direction, barometric pressure, temperature and relative humidity;
• Gas appliance details;
• House construction and age.

Houses tested ranged from new to over 100 years old, containing a large number of different heater models and types, with heat outputs ranging from 8 MJ/h to greater than 30 MJ/h.

The strength of the Study lies in the fact that observations are not theoretical values obtained from trials that can only imitate real situations, instead they are practical observations that are the outcome of actual heater use.

In summary, the UGA Study outcomes were as follows:

• When unflued gas heaters are operating, indoor air generally exhibits substantially higher levels of nitrogen dioxide, carbon dioxide and carbon monoxide than the highest concentrations measured in ambient air in Australia. The measured average peak indoor 1 hour nitrogen dioxide levels were over 10 times higher than the equivalent measured outdoor values;
• Air pollutant levels, especially for nitrogen dioxide, were often significantly above health based indoor air quality criteria;
• Measured concentrations of nitrogen dioxide substantially resulting from the use of unflued gas heaters in several Australian settings, have revealed levels in many houses well above those associated with health effects in Australian children with asthma;
• In the homes tested, the levels of nitrogen dioxide when new or near new appliances were being operated, were not significantly different to the average levels for all heaters;
• Formaldehyde levels exceeded the NHMRC indoor air quality guideline value on 2 out of 13 occasions (15%);
• The levels measured in this study were not substantially different to those found in a late 1980's study in Australian homes (Ferrari et al, 1988). This is despite the fact that many homes tested in the UGA Study were of open-plan design, thus requiring heating over a large area.

As a result of the late start to the testing programme, the sampling period did not cover the entire winter season, and extended to mid spring in Melbourne and country Victoria. It is likely that if all samples were taken in winter, the measured levels of combustion gases would have been higher than those reported, given that the indoor/outdoor temperature differential was identified as a factor associated with nitrogen dioxide levels;

Simple single parameter linear regression analysis of peak 1 hour nitrogen dioxide concentrations generally showed poor correlations with other parameters.

Multiple parameter regression analysis was conducted by John Wlodarczyk Consulting Services (JWCS). This analysis found that indoor nitrogen dioxide concentrations were strongly related to several explanatory variables. Relationships were found with indoor/ outdoor temperature differential and indoor humidity.