When dielectric materials are brought into contact and then separated, they develop static electricity. For centuries, it has been assumed that such contact charging derives from the spatially homogeneous material properties (along the material's surface) and that within a given pair of materials, one charges uniformly positively and the other negatively. We demonstrate that this picture of contact charging is incorrect. Whereas each contact-electrified piece develops a net charge of either positive or negative polarity, each surface supports a random "mosaic" of oppositely charged regions of nanoscopic dimensions. These mosaics of surface charge have the same topological characteristics for different types of electrified dielectrics and accommodate significantly more charge per unit area than previously thought.

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The Mosaic of Surface Charge in Contact Electrification

A gap in emission inventories of urban volatile organic compound (VOC) sources, which contribute to regional ozone and aerosol burdens, has increased as transportation emissions in the United States and Europe have declined rapidly. A detailed mass balance demonstrates that the use of volatile chemical products (VCPs)—including pesticides, coatings, printing inks, adhesives, cleaning agents, and personal care products—now constitutes half of fossil fuel VOC emissions in industrialized cities. The high fraction of VCP emissions is consistent with observed urban outdoor and indoor air measurements. We show that human exposure to carbonaceous aerosols of fossil origin is transitioning away from transportation-related sources and toward VCPs. Existing U.S. regulations on VCPs emphasize mitigating ozone and air toxics, but they currently exempt many chemicals that lead to secondary organic aerosols.

Volatile chemical products emerging as largest petrochemical source of urban organic emissions.

WHO Guidelines for Indoor Air Quality: Selected pollutants.

Exposure to major volatile organic compounds and carbonyls in European indoor environments and associated health risk

Emissions of organophosphate and brominated flame retardants from selected consumer products and building materials

Formaldehyde is considered as carcinogenic and is emitted from particleboards and plywood used in toy manufacturing. Currently, the flask method is frequently used in Europe for market surveillance purposes to assess formaldehyde release from toys, but its concordance to levels measured in emission test chambers is poor. Surveillance laboratories are unable to afford laborious and expensive emission chamber testing to comply with a new amendment of the European Toy Directive; they need an alternative method that can provide reliable results. Therefore, the application of miniaturised emission test chambers was tested. Comparisons between a 1 m3 emission test chamber and 44 mL microchambers with two particleboards over 28 days and between a 24 L desiccator chamber and the microchambers with three puzzle samples over 10 days resulted in a correlation coefficient r2 of 0.834 for formaldehyde at steady state. The correlation between the results obtained in microchambers vs. flask showed a high variability over 10 samples (r2: 0.145), thereby demonstrating the error-proneness of the flask method in comparison to methods carried out under ambient parameters. An exposure assessment was also performed for three toy puzzles: indoor formaldehyde concentrations caused by puzzles were not negligible (up to 8 µg/m3), especially when more conservative exposure scenarios were considered.

/pdf/formaldehyde-emissions-from-wooden-toys-comparison-of-1o1qk8zs95.pdf

Formaldehyde Emissions from Wooden Toys: Comparison of Different Measurement Methods and Assessment of Exposure.

Eco-Label for low emission wood products and wood base products (RAL-UZ-38) - Part 1: Criteria and requirements for labeling

Im vorliegenden Bericht wurden 11 Fusbodenbelagskleber, eine Grundierung, eine Spachtelmasse, 14 Teppiche, 5 PVC-Bodenbelage, drei Linoleum-Belage, ein Kautschukbelag und ein Polyolefinbelag uber einen Zeitraum von mindestens 28 Tagen mittels Prufkammer- bzw. Prufzellenmessung auf ihr Emissionsverhalten untersucht. Die Emissionsmessungen an den Einzelmaterialien Kleber und Bodenbelag sollten die moglichen Emissionen (Substanzen und Konzentrationen) und deren zeitlichen Verlauf ermitteln. Auserdem wurden die Emissionen aus 7 Materialkombinationen ermittelt. Dazu gerhorten drei Komplettaufbauten aus Estrich, Grundierung, Spachtelmasse und Kleber mit den Belagen Teppich, PVC und Linoleum sowie 4 Verbundsysteme. Dies waren: Verbundsystem Estrich/Grundierung/Spachtelmasse/Kleber, Verbundsystem Glasplatte/Kleber/Teppich, Verbundsystem Glasplatte/Kleber/PVC-Belag und das Verbundsystem Estrich/Kleber. Die Emissionen aus den Komplettbauten wueden durch Sorptionseffekte und durch die unterschiedliche Durchlassigkeit der Bodenbelage beeinflusst. Dabei waren die Emissionen aus den Komplettaufbauten und Verbundsystemen jeweils geringer als die Summe der Emissionen der entsprechenden Einzelmaterialien. Erganzende Untersuchungen wurden durchgefuhrt zur Vergleichbarkeit der Emissionsmessungen in unterschiedlichen Prufkammern (Volumen 1 m3 und 0,02 m3) bzw. Messzellen(Volumen 1 l und 0,035 l [FLEC]). und bei 42 Klebern zur Anwendbarkeit der Direkt-Thermodesorption (dynamische Headspace-Methode) als Screening-Verfahren. Des weiteren wurden Versuche durchgefuhrt, um die Auswirkungen unterschiedlicher Probenherstellung (Tragermaterial, Auftragsmenge, Auftragsart) auf die Emissionen aus den Fusbodenklebern abschhatzen konnen. Die durchgefuhrten Untersuchungen stellen eine Grundlage zur Erarbeitung eines Umweltzeichens fur Fusbodenkleber dar.

Untersuchung und Ermittlung emissionsarmer Klebstoffe und Bodenbeläge

Inter-laboratory study approach to validate the performance of a prototype reference material for product emissions testing | NIST

Most VVOC were rarely considered in the evaluation of construction products. (Salthammer, 2014) In Germany this will change because the latest version of the German AgBB scheme for health evaluation (2015) now include VVOC, e.g. ethyl acetate and ethanol. In this study selected compounds were tested with the procedure described in ISO 16017 and a method for measuring VVOC with thermal desorption was developed.
Three different adsorbents Tenax TA, Carbograph 5TD and Carbopack X were tested to analyse VVOC according to ISO 16017. For the tested VVOC, Carbograph 5TD showed the best results under the chosen analytical conditions.

Olaf Wilke

Papers

Formaldehyde Emissions from Wooden Toys: Comparison of Different Measurement Methods and Assessment of Exposure.

Eco-Label for low emission wood products and wood base products (RAL-UZ-38) - Part 1: Criteria and requirements for labeling

Untersuchung und Ermittlung emissionsarmer Klebstoffe und Bodenbeläge

Inter-laboratory study approach to validate the performance of a prototype reference material for product emissions testing | NIST

Analysis of very volatile organic compounds (VVOC) with thermal desorption GC-MS