IRF: Institutional Repository FHNW
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Neuzugänge
Knowledge blockchains: applying blockchain technologies to enterprise modeling
(2018) Fill, Hans-Georg; Härer, Felix; Bui, Tung X.
04B - Beitrag Konferenzschrift
Nanoparticle counting for PTI: the dirty tail paradigm - a pragmatic proposal to strongly reduce urban PN pollution from combustion engine fleets
(Springer, 28.01.2025) Mayer, Andreas; Czerwinski, Jan; Lutz, Thomas; Legerer, Friedrich; Wyser, Michael; Comte, Pierre; Larsen, Lars; Rubino, Lauretta; Vasilatou, Konstantina; Engelmann, Danilo; Knoll, Markus; Burtscher, Heinz
Using solid particle number (PN) measurements in the European Periodic Technical Inspection (PTI) of diesel engines equipped with particulate filters was proposed by VERT in 2016 during the Dieselgate Hearing of the Federal Republic of Germany. An international working group developed the standards and instruments for this method over 3 years under the leadership of TNO and VERT, which were next implemented in four countries, Belgium, the Netherlands, Germany, and Switzerland, starting in 2022. PN measurement is now state of the art, enabling rapid and reliable detection of possible failures in particulate filters and the need for their immediate restoration. This paper expands on that successful experience, recommending that PN counting be used for control of PN emissions from all vehicles during PTI. It reviews results from a number of earlier studies on “high emitters” and shows some new data sets for gasoline engines. Five large vehicle fleets, diesel and gasoline, heavy-duty engines (HDE), light-duty vehicles (LDV), and non-road mobile machinery (NRMM), with and without emission aftertreatment were analyzed. It was observed that, while most vehicles in working fleets are clean (i.e., meet or often are far are below their corresponding emission limits), every fleet, however, contains some high emitters, about 4–8% of the fleet hereby termed “dirty tail” — diesel as well as gasoline engines. This small fraction dominates the PN emission of the entire fleet and may increase the overall PN emission of its corresponding fleet by more than tenfold over the level of the compliant vehicles! Experience indicates that PN emission may be a strong indicator of many different deteriorations in a combustion engine and thus can be used as a highly sensitive diagnostic signal to detect various engine or emission faults quickly and reliably. This is a new understanding of emission control of vehicle fleets: not by regulations for new vehicles only which apply for all vehicles but by selecting the high emitters and consequently repair or replace these relatively few vehicles to the extent desired in terms of emissions policy. Most countries have already implemented strong periodic technical inspection systems. We suggest to expand such tests by additionally measuring the particle number concentration in the exhaust gas of all vehicles for just 1 min, thereby detecting the high emitters. With consistent annual monitoring, this procedure will reduce urban particle pollution from combustion engines to one-tenth or lower, a significant contribution to reducing local health risks.
01A - Beitrag in wissenschaftlicher Zeitschrift
Air cleaners and respiratory infections in schools: a modeling study based on epidemiologic, environmental, and molecular data
(Oxford University Press, 2024) Banholzer, Nicolas; Jent, Philipp; Bittel, Pascal; Zürcher, Kathrin; Furrer, Lavinia; Bertschinger, Simon; Weingartner, Ernest; Ramette, Alban; Egger, Matthias; Hascher, Tina; Fenner, Lukas
Background. Using a multiple-measurement approach, we examined the real-world effective-ness of portable HEPA air filtration devices (air cleaners) in a school setting.
Methods. We collected data over 7 weeks during winter 2022/2023 in 2 Swiss secondary school classes: environmental (CO2, particle concentrations), epidemiologic (absences related to res-piratory infections), audio (coughing), and molecular (bioaerosol and saliva samples). Using a crossover design, we compared particle concentrations, coughing, and risk of infection with and without air cleaners. Results. All 38 students participated (age, 13–15 years). With air cleaners, mean particle concentration decreased by 77% (95% credible interval, 63%−86%). There were no differences in CO2 levels. Absences related to respiratory infections were 22 without air cleaners vs 13 with them. Bayesian modeling suggested a reduced risk of infection, with a pos-terior probability of 91% and a relative risk of 0.73 (95% credible interval, 0.44–1.18). Coughing also tended to be less frequent (posterior probability, 93%), indicating that fewer symptomatic students were in class. Molecular analysis detected mainly non–SARS-CoV-2 viruses in saliva (50/448 positive) but not in bioaerosols (2/105) or on the HEPA filters of the air cleaners (4/160). The molecular detection rate in saliva was similar with and without air cleaners. Spatiotemporal analysis of positive saliva samples identified several likely transmissions.
Conclusions. Air cleaners improved air quality and showed potential benefits in reducing respira-tory infections. Airborne detection of non–SARS-CoV-2 viruses was rare, suggesting that these viruses may be more difficult to detect in the air. Future studies should examine the importance of close contact and long-range transmission and the cost-effectiveness of using air cleaners. Keywords. air cleaner; airborne transmission; molecular detection; respiratory viruses; schools.
01A - Beitrag in wissenschaftlicher Zeitschrift
Nanofiltration must be combined with laminar vertical flow to minimize virus infection risk
(2022) Mayer, Andreas; Mayer, J.; Burtscher, Heinz; Czerwinski, Jan; Lutz, Thomas; Mayer, R.; Rothen-Ruthishauser, Barbara; Frey, Joachim; Lämmle, Chr.; Rüggeberg, Tobias; Specht, Patrick
A SARS CoV-2 infected person may emit up to 10 million viruses with each m3 of exhaled air, and on the other hand, the infection dose may be as low as 500-1000 viruses. Given these numbers, the infection risk in a room cannot be sufficiently reduced by periodic window ventilation or by partly cleaning with mobile air cleaners but requires a continuous perfect virus elimination. Furthermore, lateral flow from the infected persons to their direct or distant neighbors must be avoided. This sounds utopic but can indeed be solved by body heat induced vertical aminar flow and ventilation from floor to the ceiling, extracting the contaminated air at the ceiling and recycling it via a filter back to the floor. Filtration must be very close to 100%. Since the « naket » Corona virus has a size of 60-150 nm, which is the typical size of particles emitted by combustion engines. The diesel particle filter DPF, a honeycomb type ceramic wall-flow filter, was selected for this nanofiltration task. These filters reach > 99% efficiency for soot particles of 10-500 nm and have attractive properties since their filtration surface is > 1 m2 per liter bulk volume, they can easily be cleaned in situ, if needed thermically disinfected or catalytically coated, and have the life, the quality, low bulk and low cost of an automotive product. To test the bioaerosol filtration properties, bacteriophages MS2, which are non-pathogenic to human, animals and plants and have a viral particle size of 30-40nm were used for the test as a proxy for SARS-CoV-2 virus. The wall flow filters reached a filtration rate of >99 % for these bacteriophages and the survival test resulted in 1% active viruses after 24 hours, zero after 48 hours. To test the whole system, a classroom was selected as a pilot case. The ventilation was designed to ex-change the room’s air volume five times per hour. Contaminated air was extracted at the ceiling and recycled to the floor corners after filtration. Fresh air from outside supplied for CO2-control was also filtered to clean it from ultrafine traffic related carcinogenic particles. The dynamic cleaning process and room distribution was tested with salt nanoparticles simulating the virus source by a cloud concentration of 80'000 particles per cubic centimeter. The lateral flow reaching the neighbor desk of the infected schoolboy contained only 2-300 P/cc, demonstrating that the contaminated air escapes vertically, showing a cross-contamination risk reduction of 2-3 orders of magnitude. This virus protection system is universally applicable, not only for applications in classrooms, but can also be scaled and adapted to industry, hospitals and public transport environments including aircraft cabins.
04B - Beitrag Konferenzschrift