@article{TanHantschkeKaminskietal.2021, author = {Tan, Zhaofeng and Hantschke, Luisa and Kaminski, Martin and Acir, Ismail-Hakki and Bohn, Birger and Cho, Changmin and Dorn, Hans-Peter and Li, Xin and Novelli, Anna and Nehr, Sascha and Rohrer, Franz and Tillmann, Ralf and Wegener, Robert and Hofzumahaus, Andreas and Kiendler-Scharr, Astrid and Wahner, Andreas and Fuchs, Hendrik}, title = {Atmospheric photo-oxidation of myrcene: OH reaction rate constant, gas-phase oxidation products and radical budgets}, series = {Atmospheric Chemistry and Physics}, volume = {21}, journal = {Atmospheric Chemistry and Physics}, number = {20}, publisher = {Copernicus GmbH}, issn = {1680-7324}, doi = {10.5194/acp-21-16067-2021}, pages = {16067 -- 16091}, year = {2021}, abstract = {Abstract. The photo-oxidation of myrcene, a monoterpene species emitted by plants, was investigated at atmospheric conditions in the outdoor simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a Large Reaction Chamber). The chemical structure of myrcene consists of one moiety that is a conjugated π system (similar to isoprene) and another moiety that is a triple-substituted olefinic unit (similar to 2-methyl-2-butene). Hydrogen shift reactions of organic peroxy radicals (RO2) formed in the reaction of isoprene with atmospheric OH radicals are known to be of importance for the regeneration of OH. Structure-activity relationships (SARs) suggest that similar hydrogen shift reactions like in isoprene may apply to the isoprenyl part of RO2 radicals formed during the OH oxidation of myrcene. In addition, SAR predicts further isomerization reactions that would be competitive with bimolecular RO2 reactions for chemical conditions that are typical for forested environments with low concentrations of nitric oxide. Assuming that OH peroxy radicals can rapidly interconvert by addition and elimination of O2 like in isoprene, bulk isomerization rate constants of 0.21 and 0.097 s-1 (T=298 K) for the three isomers resulting from the 3′-OH and 1-OH addition, respectively, can be derived from SAR. Measurements of radicals and trace gases in the experiments allowed us to calculate radical production and destruction rates, which are expected to be balanced. The largest discrepancies between production and destruction rates were found for RO2. Additional loss of organic peroxy radicals due to isomerization reactions could explain the observed discrepancies. The uncertainty of the total radical (ROx=OH+HO2+RO2) production rates was high due to the uncertainty in the yield of radicals from myrcene ozonolysis. However, results indicate that radical production can only be balanced if the reaction rate constant of the reaction between hydroperoxy (HO2) and RO2 radicals derived from myrcene is lower (0.9 to 1.6×10-11 cm3 s-1) than predicted by SAR. Another explanation of the discrepancies would be that a significant fraction of products (yield: 0.3 to 0.6) from these reactions include OH and HO2 radicals instead of radical-terminating organic peroxides. Experiments also allowed us to determine the yields of organic oxidation products acetone (yield: 0.45±0.08) and formaldehyde (yield: 0.35±0.08). Acetone and formaldehyde are produced from different oxidation pathways, so that yields of these compounds reflect the branching ratios of the initial OH addition to myrcene. Yields determined in the experiments are consistent with branching ratios expected from SAR. The yield of organic nitrate was determined from the gas-phase budget analysis of reactive oxidized nitrogen in the chamber, giving a value of 0.13±0.03. In addition, the reaction rate constant for myrcene + OH was determined from the measured myrcene concentration, yielding a value of (2.3±0.3)×10-10 cm3 s-1.}, language = {en} } @article{BausNehr2022, author = {Baus, Lukas and Nehr, Sascha}, title = {Potentials and limitations of direct air capturing in the built environment}, series = {Building and Environment}, volume = {208}, journal = {Building and Environment}, publisher = {Elsevier}, issn = {0360-1323}, doi = {10.1016/j.buildenv.2021.108629}, year = {2022}, abstract = {This concept study presents an approach for resolving the trade-off between energy-efficient building operation and the provision of hygienically harmless indoor air quality. A novel coupling of HVAC-systems (heating, ventilation and air conditioning systems) with DAC-technology (direct air capturing technology) is proposed to separate CO2 in the exhaust air of buildings and recirculate the CO2-depleted air back into the building. In a mainly theoretical approach, the corresponding potentials and limitations of the novel HVAC/DAC-coupling in recirculation mode are evaluated. For that purpose, CO2-loads in the feed and exhaust air of four buildings located in Germany were measured using calibrated non-dispersive infrared (NDIR) sensors with pyroelectric detection principle. Subsequent numerical model simulations resort to typical meteorological data as well as building operation parameters grouped in different scenarios. The measurement and simulation results were assessed with regard to: (i) the unique possibilities of a HVAC/DAC-coupling in recirculation mode for the improvement of indoor air quality, (ii) the energy saving potentials through reduced air conditioning requirements enabled by a HVAC/DAC-coupling in recirculation mode, and (iii) the potential allocation of CO2 separated from building exhaust air for energetic and/or material reutilization in decentralized systems. In conclusion, a HVAC/DAC-coupling in recirculation mode can not only reduce the energy demand of buildings but also facilitates access to unutilized CO2-resources transported in the built environment and additionally offers the potential to improve indoor air quality. However, a suitable DAC module for operation in indoor air is not yet commercially available.}, language = {en} } @article{AlvarezCarslawDusanteretal.2022, author = {Alvarez, Elena G{\´o}mez and Carslaw, Nicola and Dusanter, S{\´e}bastien and Edwards, Pete and G{\´a}bor Mihucz, Viktor and Heard, Dwayne and Kleffmann, J{\"o}rg and Nehr, Sascha and Schoemacker, Coralie and Venables, Dean}, title = {Techniques for measuring indoor radicals and radical precursors}, series = {Applied Spectroscopy Reviews}, volume = {57}, journal = {Applied Spectroscopy Reviews}, number = {7}, publisher = {Informa UK Limited}, issn = {0570-4928}, doi = {10.1080/05704928.2022.2087666}, pages = {580 -- 624}, year = {2022}, abstract = {Radicals and their precursors play a central role in the chemical transformations occurring in indoor air and on indoor surfaces. Such species include OH, HO2, peroxy radicals, nitrous acid, reactive chlorine species, NO3, N2O5, Criegee intermediates, and glyoxal and methylglyoxal. Recent advances on instrumental analysis and modeling studies have demonstrated the need for a wider range of measurements of radical species and their precursors in indoor air. This work reviews measurement techniques and provides considerations for indoor measurements of several radicals and their precursors. Techniques to determine the actinic flux are also presented owing to the relevance of photolytically-initiated processes indoors. This review is also intended to provide pointers for those wanting to learn more about measurements of radicals indoors.}, language = {en} } @article{PangNovelliKaminskietal.2022, author = {Pang, Jacky Yat Sing and Novelli, Anna and Kaminski, Martin and Acir, Ismail-Hakki and Bohn, Birger and Carlsson, Philip T. M. and Cho, Changmin and Dorn, Hans-Peter and Hofzumahaus, Andreas and Li, Xin and Lutz, Anna and Nehr, Sascha and Reimer, David and Rohrer, Franz and Tillmann, Ralf and Wegener, Robert and Kiendler-Scharr, Astrid and Wahner, Andreas and Fuchs, Hendrik}, title = {Investigation of the limonene photooxidation by OH at different NO concentrations in the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber)}, series = {Atmospheric Chemistry and Physics}, volume = {22}, journal = {Atmospheric Chemistry and Physics}, number = {13}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-22-8497-2022}, pages = {8497 -- 8527}, year = {2022}, abstract = {Abstract. The oxidation of limonene by the hydroxyl (OH) radical and ozone (O3) was investigated in the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) in experiments performed at different nitric oxide (NO) mixing ratios from nearly 0 up to 10 ppbv. For the experiments dominated by OH oxidation, the formaldehyde (HCHO) yield was experimentally determined and found to be (12 ± 3), (13 ± 3), and (32 ± 5) \% for experiments with low (∼ 0.1 ppbv), medium (∼ 0.3 ppbv), and high NO (5 to 10 ppbv), respectively. The yield in an ozonolysis-only experiment was (10 ± 1) \%, which agrees with previous laboratory studies. The experimental yield of the first-generation organic nitrates from limonene-OH oxidation is calculated as (34 ± 5) \%, about 11 \% higher than the value in the Master Chemical Mechanism (MCM), which is derived from structure-activity relationships (SARs). Time series of measured radicals, trace-gas concentrations, and OH reactivity are compared to results from zero-dimensional chemical box model calculations applying MCM v3.3.1. Modeled OH reactivity is 5 to 10 s-1 (25 \% to 33 \% of the OH reactivity at the start of the experiment) higher than measured values at the end of the experiments under all chemical conditions investigated, suggesting either that there are unaccounted loss processes of limonene oxidation products or that products are less reactive toward OH. In addition, model calculations underestimate measured hydroperoxyl radical (HO2) concentrations by 20 \% to 90 \% and overestimate organic peroxyl radical (RO2) concentrations by 50 \% to 300 \%. The largest deviations are found in low-NO experiments and in the ozonolysis experiment. An OH radical budget analysis, which uses only measured quantities, shows that the budget is closed in most of the experiments. A similar budget analysis for RO2 radicals suggests that an additional RO2 loss rate constant of about (1-6) × 10-2 s-1 for first-generation RO2 is required to match the measured RO2 concentrations in all experiments. Sensitivity model runs indicate that additional reactions converting RO2 to HO2 at a rate constant of about (1.7-3.0) × 10-2 s-1 would improve the model-measurement agreement of NOx, HO2, and RO2 concentrations and OH reactivity. Reaction pathways that could lead to the production of additional OH and HO2 are discussed, which include isomerization reactions of RO2 from the oxidation of limonene, different branching ratios for the reaction of RO2 with HO2, and a faster rate constant for RO2 recombination reactions. As the exact chemical mechanisms of the additional HO2 and OH sources could not be identified, further work needs to focus on quantifying organic product species and organic peroxy radicals from limonene oxidation.}, language = {en} } @article{NehrJaeckel2023, author = {Nehr, Sascha and J{\"a}ckel, Simon}, title = {Successful Innovation Transfer through Pre-Standardization: A Case Study}, series = {Standards}, volume = {3}, journal = {Standards}, number = {1}, publisher = {MDPI}, issn = {2305-6703}, doi = {10.3390/standards3010004}, pages = {31 -- 42}, year = {2023}, abstract = {This study presents an approach to structure, analyze and evaluate corporate standardization processes using the example of pre-standardization for the reduction of environmental impacts in product design and development. For this purpose, we give a detailed description of the evolution of the European Standard EN 16524 entitled "Mechanical products—Methodology for reduction of environmental impacts in product design and development". The standardization strategy behind the evolution of EN 16524 is analyzed using the approach of a Business Model Canvas combined with an evaluation using pre-defined success factors. Moreover, we derive general recommendations for corporate standardization professionals in checklists for each field of the underlying Business Model Canvas. With regard to the case study depicted here, we come to the conclusion that pre-standards are especially suited for innovation transfer in the field of emerging and rapidly evolving scientific and technical results.}, language = {en} } @article{NehrDuarteAlmeidaetal.2023, author = {Nehr, Sascha and Duarte, Regina M. B. O. and Almeida, Antoine S. and Baus, Lukas and Bergmann, Karl-Christian}, title = {Assessing the relevance of allergenic pollen in indoor environments—current knowledge base and research needs}, series = {Allergo Journal International}, volume = {32}, journal = {Allergo Journal International}, number = {6}, publisher = {Springer Nature}, issn = {2197-0378}, doi = {10.1007/s40629-023-00251-y}, pages = {167 -- 175}, year = {2023}, abstract = {SummaryAirborne pollen allergens—a relevant component of bioaerosols and, therefore, of airborne particulate matter—are considered an important metric in air quality assessments. Although the measurement of airborne pollen allergen concentrations in outdoor environments (namely, in urban areas) has been recognized as a key environmental health indicator, no such obligation exists for indoor environments (dwellings or occupational settings). However, people spend most of their daily time (80-90\%) indoors, where the majority of their exposure to air pollution, including pollen allergens, occurs. Nonetheless, the relative importance of airborne pollen allergen exposure indoors differs from outdoors because of differences in pollen loads, sources, dispersion, and degree of penetration from the outdoor surroundings, as well as the differences in the allergenic pollen profiles. In this brief review, we mined the literature over the last 10 years to summarize what existing measurements reveal about the relevance of airborne allergenic pollen in indoor environments. The research priorities on this topic are presented, highlighting the challenges and the motivations for obtaining pollen data in built environments which are key to understand the extent and mechanisms of human exposure to airborne pollen allergens. Thus, we provide a comprehensive assessment of the relevance of airborne allergenic pollen in indoor environments, highlighting knowledge gaps and research needs related to their health effects.}, language = {en} } @article{SaffellNehr2023, author = {Saffell, John and Nehr, Sascha}, title = {Improving Indoor Air Quality through Standardization}, series = {Standards}, volume = {3}, journal = {Standards}, number = {3}, publisher = {MDPI}, issn = {2305-6703}, doi = {10.3390/standards3030019}, pages = {240 -- 267}, year = {2023}, abstract = {Human beings experience a large fraction of their exposure to air pollutants in indoor environments. Air pollution is a large environmental health risk, and exposure to ambient air pollution and indoor air pollution contribute equally to the total number of fatalities worldwide. Although legislative authorities have established limit values for ambient outdoor air and stack emissions, there are inconsistent and variable national and regional limit values for gaseous substances and airborne particulate matter in the built environment (schools, homes, healthcare facilities, offices, and other public spaces). This lack of regulation is unsurprising, because indoor spaces are characterized by complex air chemistry, and their construction materials and types of activities vary significantly. The current understanding of indoor pollutants, including short-lived oxidants, degradation of VOCs, particle formation, and particle composition, is incomplete. It is necessary to identify and assess emerging pollutants and their toxicity, and to consider new consumer products and green construction materials and their impact on indoor air quality (IAQ). Learning from IAQ surveys and audit protocols, research methodologies should be regularized for cross-research comparisons. Some indoor air quality guidance and standards have been written, and several more are in development, with the international ISO 16000 series of indoor standards leading the way for improving indoor air data quality. The WHO has established some ambient air limit values which can mostly be translated into indoor limit values. The built environment needs to harmonize energy efficiency, thermal comfort and air quality standards and guidance. In this review, we discuss the next steps for improving international, regional and national standards and guidance, leading to better and more complete indoor air quality regulations.}, language = {en} } @article{BausNehrMaeda2023, author = {Baus, Lukas and Nehr, Sascha and Maeda, Nobutaka}, title = {Investigation of CO2-Sorption Characteristics of Readily Available Solid Materials for Indoor Direct Air Capturing}, series = {Indoor Air}, volume = {2023}, journal = {Indoor Air}, editor = {Ming, Ting Zhen}, publisher = {Wiley}, issn = {1600-0668}, doi = {10.1155/2023/8821044}, pages = {1 -- 8}, year = {2023}, abstract = {Direct air capturing (DAC) is an energy demanding process for CO2-removal from air. Ongoing research focuses on the potential of indoor air as DAC-feed to profit from currently unused energetic synergies between DAC and the built environment. In this work, we investigated the performance of three different readily available, solid DAC-adsorbers under typical indoor environmental conditions of 16-25°C, 25-60\% relative humidity (RH), and CO2-concentrations of less than 800 ppm above atmospheric concentrations. The measured mass-specific CO2-adsorption capacities of K2CO3-impregnated activated carbon, polyethylenimine-snow (PEI-snow), and polyethylenimine (PEI) on silica a amount to 6.5 ± 0.3 mg g-1, 52.9 ± 4.9 mg g-1, and 56.9 ± 4.2 mg g-1, respectively. Among the three investigated adsorber materials, PEI on silica is the most promising candidate for DAC-applications as its synthesis is rather simple, the CO2-desorption is feasible at moderate conditions of about 80°C at 100 mbar, and the competing co-adsorption of water does not strongly affect the CO2-adsorption under the investigated experimental conditions.}, language = {en} } @article{CarslawBekoeLangeretal.2024, author = {Carslaw, Nicola and Bek{\"o}, Gabriel and Langer, Sarka and Schoemaecker, Coralie and Mihucz, Victor G. and Dudzinska, Marzenna and Wiesen, Peter and Nehr, Sascha and Huttunen, Kati and Querol, Xavier and Shaw, David}, title = {A new framework for indoor air chemistry measurements: Towards a better understanding of indoor air pollution}, series = {Indoor Environments}, volume = {1}, journal = {Indoor Environments}, number = {1}, publisher = {Elsevier}, issn = {2950-3620}, doi = {10.1016/j.indenv.2023.100001}, year = {2024}, language = {en} } @article{NehrBausCınaretal.2024, author = {Nehr, Sascha and Baus, Lukas and {\c{C}}{\i}nar, Hasan and Elsen, Ingo and Frauenrath, Tobias}, title = {Indoor environmental quality assessment in passively ventilated classrooms in Germany and estimation of ventilation energy losses}, series = {Journal of Building Engineering}, volume = {97}, journal = {Journal of Building Engineering}, publisher = {Elsevier}, issn = {2352-7102}, doi = {10.1016/j.jobe.2024.110937}, year = {2024}, language = {en} }