This paper investigates the role of commercially available natural building materials, including lime mortars, natural fibres and wood panels on the indoor air quality. Initially, the emissions of volatile organic compounds (VOCs) from building materials were identified and measured. Subsequent tests then considered the adsorption and re-emission behaviour of four VOCs: toluene, limonene, dodecane and formaldehyde. The significance of this paper lies in its demonstration that emissions are dependent on the chemical composition of building materials and the production process, whereas the adsorption/desorption characteristics are related to the material microstructure and the polarity of the VOCs. The results allow the performance of a construction material, in terms of its influence on indoor air quality, to be deduced from knowledge of chemical composition and microstructure. This paper provides a new approach to assessing the influence of different building materials on indoor air quality when they are exposed to gaseous pollutants.

High levels of Volatile Organic Compounds (VOCs) and extremes of Relative Humidity (RH) commonly reduce indoor air quality with associated negative effects on human health and wellbeing. Interior materials are known to be one of the main contributors to poor indoor air quality. Notwithstanding, they can also act as a sink for airborne pollutants and excess moisture through adsorption. In this paper, we evaluate the ability of Medium Density Fibreboard (MDF) modified with walnut shell to regulate RH, toluene, limonene, dodecane and formaldehyde. The physicochemical properties, including molecular size/shape, vapour pressure, polarity and boiling point of VOCs allowed them to represent a range of pollutants. Adsorption and desorption behaviour of MDF containing up to 15% walnut shell was evaluated in 2-L environmental chambers under dynamic conditions at 23 °C and 50% RH. The porous microstructure of the MDF and walnut shell and their chemical composition were analysed using SEM, XRD and FTIR. Compared to a control panel, walnut shell additions showed an improved ability to remove VOCs and formaldehyde from the indoor air and buffer humidity. Of particular significance was the irreversible sink effect of formaldehyde and dodecane. This was attributed to the porous surface of walnut shell increasing the specific surface area of the panel and thus its adsorption capacity. The improved capacity of buffer humidity also increased the ability to adsorb water soluble VOCs such as formaldehyde. This research provides for the first time significant evidence that walnut shell modified MDF can improve indoor air quality

In the present study, two photocatalytic graphene oxide (GO) and carbon nanotubes (CNT) modified TiO₂ materials thermally treated at 300 °C (T300_GO and T300_CNT, respectively) were tested and revealed their conversion efficiency of nitrogen oxides (NO_x) under simulated solar light, showing slightly better results when compared with the commercial Degussa P25 material at the initial concentration of NO_x of 200 ppb. A chemical kinetic model based on the Langmuir–Hinshelwood (L-H) mechanism was employed to simulate micropollutant abatement. Modeling of the fluid dynamics and photocatalytic oxidation (PCO) kinetics was accomplished with computational fluid dynamics (CFD) approach for modeling single-phase liquid fluid flow (air/NO_x mixture) with an isothermal heterogeneous surface reaction. A tuning methodology based on an extensive CFD simulation procedure was applied to adjust the kinetic model parameters toward a better correspondence between simulated and experimentally obtained data. The kinetic simulations of heterogeneous photo-oxidation of NO_x carried out with the optimized parameters demonstrated a high degree of matching with the experimentally obtained NO_x conversion. T300_CNT is the most active photolytic material with a degradation rate of 62.1%, followed by P25-61.4% and T300_GO-60.4%, when irradiated, for 30 min, with emission spectra similar to solar light.

This article reports a novel photocatalytic lime render for indoor and outdoor air quality improvement that is composed of a lime binder and doped TiO₂ (KRONOClean 7000^®) nanoparticles. These nanoparticles were distributed throughout the bulk of the finishing render, instead of as a thin coating, thus ensuring the durability of the photocatalytic properties upon superficial damage. The physical properties of these renders were not affected by the addition of nanoparticles except in the case of surface area, which increased significantly. In terms of their photocatalytic activity, these novel lime renders were shown to degrade up to 12% NO_x under UV light and up to 11% formaldehyde under visible light.