Total Surface Area in Indoor Environments
Certain processes in indoor air, such as deposition, partitioning, and heterogeneous reactions, involve interactions with surfaces. To accurately describe the surface-area-to-volume ratio in a room, we have characterized the surface area, volume, shape, and material of objects in five bedrooms, four kitchens, and three offices. Averaged over all types of rooms, the ratio of surface area with contents to that without contents was 1.7 ± 0.2 (mean ± standard error), and the ratio of volume of freely moving air to volume of the entire space was 0.89 ± 0.05. Ignoring contents, the surface-area-to-volume ratio was 1.9 ± 0.3 m-1; accounting for contents, the ratio was 3.7 ± 1.2 m-1. Ratios were not significantly different between room types and were comparable to those measured for 33 rooms in a similar study. Due to substantial differences in the design and contents of kitchens, their ratios had the highest variability among the three room types. On average, the contents of bedrooms, kitchens, and offices increase their surface area by 70% and decrease their volume of freely moving air by 11% compared to an empty room. The most common shape of objects in a room was a flat plate, while each room also had many irregularly-shaped objects. Paint and wood were the two most common materials in each room, although the distribution of materials varied by room type. The results of this study can be used to improve understanding of the behavior of gases and particles in indoor environments.