Experimental investigation of indoor air pollutants in three residential buildings

• Main Author: Tan, Caren
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2012
• Subjects: Environmental engineering

We spend about 90% of our time inside buildings, where we control the quality of the environment for health, thermal comfort, security and productivity. The quality of the indoor environment is affected by many factors including the design of the building, ventilation, thermal insulation and energy provision and use. To improve thermal comfort and reduce energy consumption, the inside environment has been almost completely isolated from the outside environment in recent years, through making buildings airtight. However, as dwellings are made more airtight internal pollution sources (such as heating and cooking) can have a greater impact on the indoor air quality and occupants may experience adverse health effects. The main objective of this research was therefore to investigate indoor air pollutant emissions in relation to energy use in residential buildings, with a focus on particulate matter (PM). Three environments were investigated: (i) a rural house with an electric cooker; (ii) a citycentre flat with a gas cooker; and (iii) an urban flat on a main road, also with gas appliances. Concentrations of PM, carbon monoxide (CO), nitrogen dioxide (NO2) and volatile organic compounds (VOCs) were measured in the kitchens and enhanced emission rates were calculated for cooking periods. Although there has been a great deal of research examining the effects of gaseous pollutants in the indoor environment, this is the first study to focus on PM. This study showed that most particulates were small (≤2.5μm) and thus respirable. The elemental analysis of the PM revealed high metal concentrations (Fe/Na/Zn), whilst their morphologies indicated these were present as salt, skin flakes and mineral fibres. Cooking activities were found to directly contribute to PM2.5 emissions in the indoor environment. In the kitchen of the rural house with the electrical cooker, PM2.5 emission rates ranged from 5 to 22 mg/hr. The city centre flat with a gas cooker had higher PM2.5 concentrations and thus also greater emission rates (up to 54 mg/hr). CO concentrations were generally quite low - around 1-2 ppm in all three residential environments. During cooking however, the CO levels became elevated in the kitchens with the gas cookers (Cases 2 and 3), as this was a significant source of this species; levels often peaked at 10-20 ppm during cooking. For Case 1, where an electric cooker was installed, there was no difference in CO levels during cooking and non-cooking periods. In the rural house (Case 1), since there was no source of NO2 emissions inside, the indoor and outdoor NO2 concentrations were the same, around 10-11 μg/m³. However in the city-centre flat (Case 2), the gas cooker was found to be a significant source of NO2 and thus the indoor concentration was much greater than the outdoor levels (47 μg/m³ compared to 15 μg/m³) and the resultant indoor emission rate was also high - up to 65.5 mg/hr. The VOC concentrations were consistently higher in the indoor environments at all locations compared to outdoor levels. The highest emission rate for VOCs was for the kitchen of Case 2, the city-centre flat (~ 43 mg/hr). This study has shown that indoor air quality is influenced by fuel, type of cooker, and cooking method. Air quality in residential buildings, especially in the kitchen, was generally poorer when using gas appliances compared to when an electric cooker was used; this was true for both solid and gas-phase pollutants. In addition, indoor air was strongly influenced by outdoor sources of pollution.