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Abstract: While indoor air quality issues have received increasing attention the past decades, detailed investigations of primary sources of indoor pollution are still difficult to carry out. There is a lack of analytical tools and measurement procedures to identify sources of pollutants and to characterize their emissions. Formaldehyde is a ubiquitous pollutant in indoor environments, which is known to lead to adverse health effects. This study describes a measurement procedure to apportion formaldehyde emissions from building and furnishing materials and presents a source apportionment study performed in French public schools. More than 29 sources of formaldehyde were characterized in each investigated classroom, with higher emissions from building materials compared to furnishing materials. Formaldehyde emission rates measured using passive flux samplers (PFS) range from 1.2 to 252 μg/m2/h, highlighting several strong emitters made of wood products and foam. Interestingly, the ceiling was identified as the main source of formaldehyde in most classrooms. Measured emissions and air exchange rates were constrained in a mass balance model to evaluate the impact of formaldehyde reduction strategies. These results indicate that formaldehyde concentrations can be reduced by 87–98% by removing or replacing the main source of emission by a less emissive material and by increasing the air exchange rate to 1 h−1. In addition, an intercomparison of total emissions calculated from (1) PFS measurements and from (2) measured formaldehyde concentrations and air exchange rates indicate that an unidentified sink of formaldehyde may exist in indoor environments. [Copyright &y& Elsevier]

Over the last 30 years, several experimental chambers were developed and implemented for indoor air studies. Yet, they were not all representative of real indoor air conditions. Either they did not have sufficient volumes or they were hindered by difficulties to control experimental conditions and air exchange rates. In this context, a 40 m 3 Innovative experimental Room for Indoor Air studies (IRINA) has been developed and validated at Mines Douai (Atmospheric Sciences et Environmental Engineering department (SAGE)) to overcome these drawbacks and above all to perform reproducible indoor air studies avoiding any possible experimental biases. IRINA inner walls are covered with aluminum foils. The room is operated in a closed mode and is equipped with a VOC injection system that relies on the heated and pressurized injection of vaporized VOC. IRINA is also equipped with analytical instruments that allow the analysis of both gas (online and offline measurements) and particle phases. IRINA validation evidenced that: (i) the air exchange rate of the room is well controlled over an one year timespan; (ii) both gaseous and particulate background levels in IRINA remain lower than typical indoor air conditions; (iii) fast homogenization of injected VOC concentrations is reached in the room; (iv) adsorption phenomena on IRINA walls are limited; and (v) there is no VOC matrix impact regarding individual VOC decays. The modelling of VOC natural decay in IRINA based on the new INCA-Indoor model showed that the VOC removal in IRINA is mainly due to the air exchange rate. [ABSTRACT FROM AUTHOR]

This study investigates the photocatalytic oxidation of limonene, used as a model terpenoid, close to indoor air conditions. Besides the characterization of limonene removal kinetic on the ppb range, special attention has been paid to reaction intermediates and by-products: (i) in the gas phase, (ii) in the adsorbed phase and (iii) in the particulate phase. All along the oxidation reaction organic reaction intermediates have been monitored. Despite a high conversion rate of limonene after 10 h of treatment, 20 primary and secondary reaction intermediates were detected and quantified in the gas phase with acetone and acetaldehyde as the most abundant ones. The characterization of limonene adsorbed on TiO 2 surface under UV illumination using DRIFTS pointed out the fact that the photocatalyst surface acts as a pool of heavy reaction intermediates, close to terpenoid structure, which may be responsible for the release of some secondary reaction intermediates. The mineralization of limonene has been assessed during the whole oxidation process through CO and CO 2 monitoring. CO 2 formation is observed more than 12 h beyond limonene complete removal, confirming the long term oxidation of the adsorbed phase. The photocatalytic heterogeneous formation of secondary organic aerosol is reported for the first time. A massive production of SOA since the first steps of limonene photocatalytic oxidation is evidenced. Based on the quantitative analyses performed, carbon mass balances have been calculated along the oxidation reaction advancement. The highest contributions of organic reaction intermediates and SOA in the carbon balance are respectively 12% and 1.6%. When limonene is removed from the gas phase, more than 60% of the carbon balance remains unidentified but this contribution can be mainly attributed to the adsorbed organic species. After 24 h of treatment, almost 75% of the organics are mineralized into CO 2 . [ABSTRACT FROM AUTHOR]