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Processes based on non-thermal plasma (NTP) for indoor air treatment inevitably lead to the formation of toxic by-products such as ozone (O 3 ) and nitrogen oxides (NO x ). Adding a step of heterogeneous catalysis in series with NTP could allow for the decomposition of the by-products. Therefore, different catalysts were developed based on transition metal oxides, such as NiO x , CoO x and MnO x with different weight percentage 1, 5 and 10wt.%, deposited on a γ-Al 2 O 3 support. The O 3 removal efficiency (ORE) and the NO x removal efficiency (NRE) were very encouraging in dry air: about 65% and 80%, respectively, by using 2g 5wt.% MnO x /Al 2 O 3 catalyst under the experimental conditions. However, strongly negative effects of relative humidity (RH) on the catalytic decomposition performance were observed. To overcome this limitation, the catalyst surface was modified to make it hydrophobic using a cost-effective chemical grafting method. This treatment consisted in impregnating the 5wt.% MnO x /Al 2 O 3 catalyst with different trichloro(alkyl)silanes (TCAS). The effects of different linker lengths and amounts of TCAS for the hydrophobicity and the decomposition performance of surface-modified catalysts under humid conditions were investigated. Our results show that the surface-modified catalyst with the shortest linker and 0.25mmol/g cat of modifying agent represents the best catalytic decomposition performance for O 3 . Its ORE is 41% at 60% RH, which is twice that of the non-modified catalyst., (Copyright © 2017. Published by Elsevier B.V.)

Background and gaps. The topic of indoor air quality (IAQ) in low-energy buildings has received increasing interest over the past few years. Often based on two measurement points and on passive measurements over one week, IAQ studies are struggling to allow the calculation of pollutants exposure. Objectives. We would like to improve the evaluation of the health impacts, through measurements able to estimate the exposure of the occupants. Methodology. This article presents detailed IAQ measurements taken in an energy-efficient occupied house in France. Two campaigns were conducted in winter and spring. Total volatile organic compounds (TVOC), formaldehyde, the particle numbers and PM2.5, carbon dioxide (CO2), relative humidity (RH), temperature (T), ventilation airflows, and weather conditions were dynamically measured in several points. Laboratory and low-cost devices were used, and an inter-comparison was carried out for them. A survey was conducted to record all the daily activities of the inhabitants. IAQ performance indicators based on the different pollutants were calculated. Results. PM2.5 cumulative exposure did not exceed the threshold available in the literature. Formaldehyde concentrations were high, in the kitchen, where the average concentrations exceeded the threshold. However, the formaldehyde cumulative exposure of the occupants did not exceed the threshold. TVOC concentrations were found to reach the threshold. With these measurements performed with high spatial and temporal discretization, we showed that such detailed data allow for a better-quality health impacts assessment and for a better understanding of the transport of pollutants between rooms. [ABSTRACT FROM AUTHOR]

• An ESP containing corona needles was proposed for indoor air treatment. • Fractional efficiency was measured for particles of 10 nm–10 µm in diameter. • Geometric, environmental and operating parameters were investigated. • In the MPPS, the fractional efficiency was higher than 99%. • The partial charging regime was highlighted. An electrostatic precipitator was evaluated to reduce nanometric and micron-sized particles in indoor air environments. This process consists in a negative air ionizer assisted by a parallel-plate collector. The ionization stage contained four or eight corona needles, which were supplied by a negative high-voltage DC. The collection stage was designed in a plate-to-plate configuration, of which the plates are alternately connected to a high-voltage DC supply and the ground. Fractional efficiency (expressed in number) was investigated using NaCl ultrafine particles and atmospheric aerosol according to different geometric, environmental and operating parameters (concentration, relative humidity, collector and ionizer voltage, collector length, number of needles, and airflow rates). The results are discussed according to particle size. Under optimized conditions (eight needles, 20 cm collector length, −7 kV ionization voltage, 5 kV collection voltage, 1 m/s air velocity), the process revealed high performance levels. The efficiency of particles of 10–25 nm in diameter was 94%, between 30 and 300 nm the efficiency was 99%, while in the most penetrating particle size, the efficiency was 96%, with an ozone concentration at the outlet of the process less than 5 ppbv. This process generated a very low ozone concentration, which is an essential challenge for indoor air treatment. The results confirmed the existence of the partial charging regime for particles less than a few tens of nanometers for which the efficiency was lower. For these particles, the collection conditions (collection time and voltage) had no influence on the efficiency. For larger particles, both the parameters of the charging phase (ion concentration, charging time) and the parameters of the collection phase (collection time and voltage) had a significant influence on the collection efficiency. [ABSTRACT FROM AUTHOR]