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 two-litre 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. 2Of 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. KeywordsVolatile organic compounds, Adsorption/desorption, Medium density fibre board, Walnut shell, Moisture buffering, Occupant health and wellbeing.

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The increased effort to improve energy efficiency, has led to improved "airtightness" of buildings, therefore leading to a reduction in ventilation. This results in an increase in concentration of indoor air pollutants, namely formaldehyde and volatile organic compounds (VOCs), which are suspected to contribute to "sick building syndrome" (SBS). There has been considerable research into the reduction of emissions via modification of current construction products. One modification is to use solid additives, "scavengers" in wood-based panels. This paper examines the effects of these scavengers on mould growth and the absorption of the VOCs; toluene, limonene and formaldehyde. The effects of the sorption of VOCs on the colonisation and growth of different mould species on modified MDF panels were also studied. It was shown that modified boards absorbed the 3 VOCs tested and this absorption did effect mould growth with differences observed in species present and in succession of mould colonisation. INTRODUCTION In recent years, indoor air quality and volatile organic compounds (VOCs) have received increasing attention. Coupled with this, there is an increased effort to improve the energy efficiency of buildings, which has resulted in the improved "air tightness" of buildings. An adverse effect of this, however, is the increase in the concentration of air pollutants, such as VOCs, inside homes where concentrations of many pollutants can be higher than in the outdoor environment (Rong et al., 2002). These VOCs often cause sick building syndrome (SBS) and have a number of symptoms; dizziness, eye and lung irritation, nausea and depression (Zhang and Xu, 2003). Therefore, indoor air quality has become an issue of public health (Kim et al., 2011). The World Health Organisation defines VOCs as compounds with a boiling point between 50 o C to 260 o C (WHO, 1989), which encompasses a great variety of compounds including, hydrocarbons, terpenes and aromatic hydrocarbons. Therefore it is an immense challenge to develop a product that will act as a sink to all VOCs. Historically, there has been considerable research into the reduction of emissions from their original source, such as odourless paints and replacing formaldehyde based resins with biobased resins during wood-based panel production. More recently, there have been investigations into modifying wood-based construction materials and insulation materials to actively absorb formaldehyde and VOCs from the atmosphere.