High roughness and porosity of indoor surfaces increases sorption capacity and may impact indoor air quality.

Surface properties impact indoor gas-surface interactions and thus indoor air quality. Specific surface area impacts sorption capacity, while pores increase diffusion and storage in the bulk material. We measured roughness, porosity, and specific surface area of eleven common indoor surfaces and calculate the sorption capacity of an authentic office space. The specific surface area of the office is four orders of magnitude greater than the geometric surface area typically considered in indoor studies. Paint decreases the specific surface area for wood and drywall. Due to the substantial sorption capacity, surface films may be patchworks of organic and water-rich layers instead of spatially-ubiquitous, multilayer organic films on top of all indoor surfaces. The pores within surfaces can enhance diffusion resulting in different bulk diffusion equilibration timescales for different surfaces with ceiling tile, carpet and wood require longer timescales (up to years) to equilibrate. Thus, easily cleaned dust and surface films can increase short-term uptake of gas-phase contaminants then be removed to reduce re-emission; however, those contaminants may still penetrate deeper into the indoor building material that cannot be removed by surface cleaning. More solid surfaces with lower sorption capacity and longer diffusive timescales improve air quality in the long term by decreasing the gas-phase contaminants stored on surfaces that can be later re-emitted. Our results imply that building material selection may decrease long-term exposure to wildfire smoke or other air pollutants.