Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) transmission lead to the recommendation of mask wearing during the pandemic COVID-19. Bacterial filtration efficiency (BFE) measurements ...are used to measure the efficiency of medical face masks in preventing the spread of bioaerosols. Even though these measurements are simple, BFE testing still raise several scientific questions. This paper presents an inter-laboratory comparison between Bacterial Filtration Efficiency (BFE) and Particle Filtration Efficiency (PFE), in order to better understand and establish an overview of both ways for testing surgical masks. Filtration efficiency of six commercial surgical masks have been measured using such experimental methods, i.e., the BFE and the PFE using 3 µm particles initially developed for community face covering testing. The fractional filtration efficiencies have been measured and compared in order to explain the differences. Recommendations for improving associated EN14683:2019+AC standard are also proposed according to the results.
During the recent pandemic of SARS-CoV-2, and as a reaction to the worldwide shortage of surgical masks, several countries have introduced new types of masks named ＂community face coverings＂ (CoFC). ...To ensure the quality of such devices and their relevance to slow down the virus spreading, a quick reaction of the certification organisms was necessary to fix the minimal acceptable performances requirements. Moreover, many laboratories involved in the aerosol research field have been asked to perform tests in a quick time according to (CEN, 2020) proposed by the European committee for standardization. This specification imposes a minimal air permeability of 96 L m^(-2) s^(-1) for a 100 Pa pressure drop and a minimal filtration efficiency of 70% for 3 μm diameter particles. In the present article, an intercomparison of efficiencies and permeabilities measured by 3 laboratories has been performed. Results are in good agreement considering the heterogeneity of the material samples (within 27% in terms of filtration efficiency and less than 20% in terms of permeability). On this basis, an analysis of 233 materials made of woven, non-woven and mixed fibrous material has been done in terms of filtration efficiency and air permeability. For some of them, measurements have been performed for 0.2 μm, 1 μm and 3 μm particle diameters. As expected, no deterministic correlation could be determined to link these efficiencies to the permeability of the considered samples. However, a trend could be identified for woven and mixed materials with an increase of filtration efficiency when the air permeability decreases. The same exercise has been conducted to link the filtration efficiency measured at 3 μm to the one for lower diameters. Finally, a discussion on the kind of material that is the most relevant to manufacture CoFC supported by spectral filtration efficiency values (from 0.02 μm to 3 μm) is proposed.
Biogenic volatile organic compounds (BVOCs) are intensely emitted by forests and crops into the atmosphere. They can rapidly react with the nitrate radical (NO.sub.3) during the nighttime to form a ...number of functionalized products. Among them, organic nitrates (ONs) have been shown to behave as reservoirs of reactive nitrogen and consequently influence the ozone budget and secondary organic aerosols (SOAs), which are known to have a direct and indirect effect on the radiative balance and thus on climate.
Biogenic volatile organic compounds (BVOCs) are intensely emitted by forests and crops into the atmosphere. They can
rapidly react with the nitrate radical (NO3) during the nighttime to form a
number ...of functionalized products. Among them, organic nitrates (ONs) have
been shown to behave as reservoirs of reactive nitrogen and consequently
influence the ozone budget and secondary organic aerosols (SOAs), which are
known to have a direct and indirect effect on the radiative balance and
thus on climate. Nevertheless, BVOC + NO3 reactions remain poorly understood. Thus,
the primary purpose of this study is to furnish new kinetic and mechanistic
data for one monoterpene (C10H16), terpinolene, and one
sesquiterpene (C15H24), β-caryophyllene, using simulation
chamber experiments. These two compounds have been chosen in order to
complete the few experimental data existing in the literature. Rate
constants have been measured using both relative and absolute methods. They
have been measured to be (6.0 ± 3.8) ×10-11 and (1.8 ± 1.4) ×10-11 cm3 molec.−1 s−1 for
terpinolene and β-caryophyllene respectively. Mechanistic studies
have also been conducted in order to identify and quantify the main reaction
products. Total organic nitrates and SOA yields have been determined. Both
terpenes appear to be major ON precursors in both gas and particle phases
with formation yields of 69 % for terpinolene and 79 % for β-caryophyllene respectively. They are also major SOA precursors, with
maximum SOA yields of around 60 % for terpinolene and 90 % for β-caryophyllene. In order to support these observations, chemical analyses
of the gas-phase products were performed at the molecular scale using
a proton transfer reaction–time-of-flight–mass spectrometer (PTR-ToF-MS) and FTIR. Detected products allowed proposing chemical mechanisms
and providing explanations through peroxy and alkoxy reaction pathways.
Residential biomass burning for heating purposes is an important source of air pollutants during winter. Here we test the hypothesis that significant secondary organic aerosol production can take ...place even during winter nights through oxidation of the emitted organic vapors by the nitrate (NO3) radical produced during the reaction of ozone and nitrogen oxides. We use a mobile dual smog chamber system which allows the study of chemical aging of ambient air against a control reference. Ambient urban air sampled during a wintertime campaign during nighttime periods with high concentrations of biomass burning emissions was used as the starting point for the aging experiments. Biomass burning organic aerosol (OA) was, on average, 70 % of the total OA at the beginning of our experiments. Ozone was added in the perturbed chamber to simulate mixing with background air (and subsequent NO3 radical production and aging), while the second chamber was used as a reference. Following the injection of ozone, rapid OA formation was observed in all experiments, leading to increases in the OA concentration by 20 %–70 %. The oxygen-to-carbon ratio of the OA increased on average by 50 %, and the mass spectra of the produced OA was quite similar to the oxidized OA mass spectra reported during winter in urban areas. Furthermore, good correlation was found for the OA mass spectra between the ambient-derived emissions in this study and the nocturnal aged laboratory-derived biomass burning emissions from previous work. Concentrations of NO3 radicals as high as 25 ppt (parts per trillion) were measured in the perturbed chamber, with an accompanying production of 0.1–3.2 µg m−3 of organic nitrate in the aerosol phase. Organic nitrate represented approximately 10 % of the mass of the secondary OA formed. These results strongly indicate that the OA in biomass burning plumes can chemically evolve rapidly even during wintertime periods with low photochemical activity.
Biogenic volatile organic compounds (BVOCs) are intensely
emitted by forests and crops into the atmosphere. During the night, they
react very rapidly with the nitrate radical (NO3), leading to the
...formation of a variety of functionalized products including organic nitrates
and to large amounts of secondary organic aerosols (SOAs). Organic nitrates
(ONs) have been shown not only to play a key role in the transport of reactive
nitrogen and consequently in the ozone budget but also to be important
components of the total organic-aerosol mass, while SOAs are known to play a direct
and indirect role in the climate. However, the reactivity of BVOCs with
NO3 remains poorly studied. The aim of this work is to provide new
kinetic and mechanistic data for two monoterpenes (C10H16),
α- and γ-terpinene, through experiments in simulation
chambers. These two compounds, which have very similar chemical structures,
have been chosen in order not only to overcome the lack of experimental data but also to
highlight the influence of the chemical structure on the reactivity. Rate constants have been measured using both relative and absolute methods.
They were found to be (1.2±0.5)×10-10 and (2.9±1.1)×10-11 cm3 molecule−1 s−1 for α- and γ-terpinene respectively. Mechanistic studies have
also been conducted in order to identify and quantify the main reaction
products. Total organic nitrate and SOA yields have been determined. While
organic nitrate formation yields appear to be similar, SOA yields exhibit
large differences with γ-terpinene being a much more efficient
precursor of aerosols. In order to provide explanations for this difference, chemical analysis of the gas-phase products was performed at the molecular scale. Detected products allowed for proposing chemical mechanisms and providing explanations through peroxy and alkoxy reaction pathways.
An incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) technique has been developed for the in situ monitoring of NO3 radicals at the parts per trillion level in the CSA simulation ...chamber (at LISA). The technique couples an incoherent broadband light source centered at 662 nm with a high-finesse optical cavity made of two highly reflecting mirrors. The optical cavity which has an effective length of 82 cm allows for up to 3 km of effective absorption and a high sensitivity for NO3 detection (up to 6 ppt for an integration time of 10 s). This technique also allows for NO2 monitoring (up to 9 ppb for an integration time of 10 s). Here, we present the experimental setup as well as tests for its characterization and validation. The validation tests include an intercomparison with another independent technique (Fourier-transform infrared, FTIR) and the absolute rate determination for the reaction trans-2-butene + NO3, which is already well documented in the literature. The value of (4.13 ± 0.45) × 10-13 cm3 molecule-1 s-1 has been found, which is in good agreement with previous determinations. From these experiments, optimal operation conditions are proposed. The technique is now fully operational and can be used to determine rate constants for fast reactions involving complex volatile organic compounds (VOCs; with rate constants up to 10-10 cm3 molecule-1 s-1).
En 2020, la communauté scientifique et l'Organisation mondiale de la santé confirmaient le risque de transmission aérienne du coronavirus Sars-CoV-2. En raison de la pénurie mondiale de masques, ...plusieurs pays ont introduit de nouveaux types de protection. Dans ce contexte, la Commission européenne a identifié le besoin urgent d'harmoniser les exigences en la matière, notamment en termes de performances de filtration et de confort associées au port du masque. Un guide de l'Afnor et un guide européen CEN ont alors été élaborés ; et, en lien avec les demandes des pouvoirs publics français formulées pendant le premier confinement, en 2020, le LNE a été mobilisé afin de répondre à la question centrale de l'efficacité des masques de protection apportant en la matière toute son expertise en métrologie des aérosols. Pour ce faire, une plateforme expérimentale a été développée en un temps record pour évaluer l'efficacité de filtration de différents types de masques de protection. Ce nouveau moyen d'essai permet, depuis le début de la crise, d'accompagner les pouvoirs publics, les industriels et les importateurs dans la qualification des masques FFP2, chirurgicaux, barrières et grand public. Dans cet article, nous présentons le banc expérimental développé par le LNE pour réaliser les mesures d'efficacité de filtration des masques barrières et grand public, ainsi que les comparaisons inter-laboratoires organisées dans ce cadre. En termes de perspectives, des axes d'amélioration du contexte normatif associé à chaque type de masques sont également présentés.
En 2020, la communauté scientifique et ^'Organisation mondiale de la santé confirmaient le risque de transmission aérienne du coronavirus Sars-CoV-2. En raison de la pénurie mondiale de masques, ...plusieurs pays ont introduit de nouveaux types de protection. Dans ce contexte, la Commission européenne a identifié le besoin urgent d'harmoniser les exigences en la matiere, notamment en termes de performances de filtration et de confort associées au port du masque. Un guide de l'Afnor et un guide européen CEN ont alors été elabores ; et, en lien avec les demandes des pouvoirs publics français formulées pendant le premier confinement, en 2020, le LNE a été mobilisé afin de répondre â la question centrale de l'efficacité des masques de protection apportant en la matiere toute son expertise en métrologie des aérosols. Pour ce faire, une plateforme expérimentale a été développée en un temps record pour évaluer l'efficacité de filtration de différents types de masques de protection. Ce nouveau moyen d'essai permet, depuis le début de la crise, d'accompagner les pouvoirs publics, les industriels et les importateurs dans la qualification des masques FFP2, chirurgicaux, barrieres et grand public. Dans cet article, nous présentons le banc expérimental développé par le LNE pour réaliser les mesures d'efficacité de filtration des masques barrieres et grand public, ainsi que les comparaisons inter-laboratoires organisées dans ce cadre. En termes de perspectives, des axes d'amélioration du contexte normatif associé a chaque type de masques sont également présentés.
An incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) technique has been developed for the in situ monitoring of NO.sub.3 radicals at the parts per trillion level in the CSA ...simulation chamber (at LISA). The technique couples an incoherent broadband light source centered at 662 nm with a high-finesse optical cavity made of two highly reflecting mirrors. The optical cavity which has an effective length of 82 cm allows for up to 3 km of effective absorption and a high sensitivity for NO.sub.3 detection (up to 6 ppt for an integration time of 10 s). This technique also allows for NO.sub.2 monitoring (up to 9 ppb for an integration time of 10 s). Here, we present the experimental setup as well as tests for its characterization and validation. The validation tests include an intercomparison with another independent technique (Fourier-transform infrared, FTIR) and the absolute rate determination for the reaction trans-2-butene + NO.sub.3, which is already well documented in the literature. The value of (4.13 ± 0.45) x 10.sup.-13 cm.sup.3 molecule.sup.-1 s.sup.-1 has been found, which is in good agreement with previous determinations. From these experiments, optimal operation conditions are proposed. The technique is now fully operational and can be used to determine rate constants for fast reactions involving complex volatile organic compounds (VOCs; with rate constants up to 10.sup.-10 cm.sup.3 molecule.sup.-1 s.sup.-1).
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