INDOOR AIR QUALITY DURING SLEEP PERIOD IN RESIDENTIAL BUILDING

Abstract

Both indoor air environment and sleeping are two important factors for a person’s well-being and performance. Indoor air environment has the potential in causing sick building syndrome while having a good night’s sleep is vital for maintaining adequate daytime performance. One of the factors that affect sleep quality is the sleeping environment. In Singapore, there is increasing residential dwellings have adopted the use of air-conditioners due to the increasing affluence of the people and the hot weather. The domestic air-conditioners used at home usually have no fresh air intake, leading to constant build-up of carbon dioxide in the room. This causes displacement of oxygen in a confined space, which may affect the sleeping duration. Therefore, there is a need to find out if the thermal conditions and indoor air quality of the bedrooms have any associations with sleep quality. Objective measurements were carried out in 24 bedrooms over a period of 1 month to find out the indoor air quality of the bedrooms during sleep period. There are two types of bedrooms, an air-conditioned (AC) one and a naturally or mechanically ventilated (NMV) one. A questionnaire survey was also distributed to each subject at the end of the objective measurement to assess their perceptions on the thermal comfort, inhaled air quality of the bedrooms during sleep and their sleeping conditions. It was found that although the mean AC temperatures were within the recommended limits, there were complaints of poor sleep. On the other hand, there was no complaint of poor sleep even though the mean NMV temperatures were not within the acceptable limit. This proved that NMV environment was a better sleeping environment as compared to an AC one. In addition, it was found that there was a considerable increase in carbon dioxide level in an AC bedroom as compared to a NMV bedroom. However, there was no clear evidence that showed that the sleeping duration deceased with increasing level of carbon dioxide, but it suggested that high level of carbon dioxide may hinder the duration of sleep. However, this set of findings cannot be generalised because of the specific age group chosen.