Articoli di riviste: "Filtres – Humidité"

1

Aqueveque, Pablo, Macarena Díaz, Britam Gomez, Rodrigo Osorio, Francisco Pastene, Luciano Radrigan e Anibal Morales. "Embedded Electronic Sensor for Monitoring of Breathing Activity, Fitting and Filter Clogging in Reusable Industrial Respirators". Biosensors 12, n. 11 (8 novembre 2022): 991. http://dx.doi.org/10.3390/bios12110991.

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Millions of workers are required to wear reusable respirators in several industries worldwide. Reusable respirators include filters that protect workers against harmful dust, smoke, gases, and vapors. These hazards may cause cancer, lung impairment, and diseases. Respiratory protection is prone to failure or misuse, such as wearing respirators with filters out of service life and employees wearing respirators loosely. Currently, there are no commercial systems capable of reliably alerting of misuse of respiratory protective equipment during the workday shifts or provide early information about dangerous clogging levels of filters. This paper proposes a low energy and non-obtrusive functional building block with embedded electronics that enable breathing monitoring inside an industrial reusable respirator. The embedded electronic device collects multidimensional data from an integrated pressure, temperature, and relative humidity sensor inside a reusable industrial respirator in real time and sends it wirelessly to an external platform for further processing. Here, the calculation of instantaneous breathing rate and estimation of the filter’s respirator fitting and clogging level is performed. The device was tested with ten healthy subjects in laboratory trials. The subjects were asked to wear industrial reusable respirator with the embedded electronic device attached inside. The signals measured with the system were compared with airflow signals measured with calibrated transducers for validation purposes. The correlation between the estimated breathing rates using pressure, temperature, and relative humidity with the reference signal (airflow) is 0.987, 0.988 and 0.989 respectively, showing that instantaneous breathing rate can be calculated accurately using the information from the embedded device. Moreover, respirator fitting (well-fitted or loose condition) and filter’s clogging levels (≤60%, 80% and 100% clogging) also can be estimated using features extracted from absolute pressure measurements combined to statistical analysis ANOVA models. These experimental outputs represent promising results for further development of data-driven prediction models using machine learning techniques to determine filters end-of-service life. Furthermore, the proposed system would collect relevant data for real-time monitoring of workers’ breathing conditions and respirator usage, helping to improve occupational safety and health in the workplace.

2

Widziewicz-Rzońca, Kamila, Sławomir Janas, Barbara Błaszczak, Monika Błaszczak, Halina Pyta, Patrycja Rogula-Kopiec, Barbara Mathews e Krzysztof Klejnowski. "ADVANCING THE UNDERSTANDING OF PM FILTER MASS STABILITY: UNVEILING THE INFLUENCE OF HUMIDITY AND TEMPERATURE". Zeszyty Naukowe Pro Publico Bono 1, n. 1 (13 novembre 2023): 7–26. http://dx.doi.org/10.5604/01.3001.0053.9741.

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The intricate interplay between humidity and temperature on PM filter performance has remaineda subject of profound scientific interest. By employing fully-automated weighing method anda two-factor regression model, the study aimed to evaluate mass variations of unloaded PM filtersunder diverse humidity and temperature conditions. Existing guidelines, as posited by the USEPA and the European Standard (EN), have demonstrated a pronounced disparity. The US EPAadvocates a narrow humidity range of 30–40% RH, while the EN suggests a broader range of40–50% RH. The results of this investigation confirm the US EPA’s guidelines, which exhibitedsuperior filter mass stability under varying humidity. In controlled stable temperature conditionsof 20C, the research unveiled significant variations in filter mass as RH% increased from 50%to 55%. It has been proven that under stable temperature conditions (20C) inside a weighingrobot, an increase in relative air humidity from 50% to 55% results in filters mass addition by15 μg (Q, quartz fibre filters); by 93 μg (PTFE filters); by 9 μg (G, glass fibre filters); by 112 μg (PA,polyamide filters) and by 20 μg (PC, polycarbonate filters). Further exploration of the conditioningranges prescribed by the EN 12341:2014 standard, the study highlighted glass fibre filters as beingnotably stable, while polyamide membrane filters posed intriguing challenges potentially relatedto ionization insufficiencies during the equilibration stage. These findings bear significance forfilter manufacturing and conditioning protocols, potentially enhancing the precision of air qualitymonitoring practices.

3

Myers, David L., e B. Dean Arnold. "Electret Media for HVAC Filtration Applications". International Nonwovens Journal os-12, n. 4 (dicembre 2003): 1558925003os—12. http://dx.doi.org/10.1177/1558925003os-1200412.

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Air filters produced with charged, or electret, media for HVAC filtration applications have gained significant market share and acceptance over the past few years. While these filters provide the advantage of high initial efficiency and low pressure drop, there are concerns about their ability to maintain efficiency in service. Furthermore, there is a tendency to classify all electret media in the same general category without any consideration of media structure, fiber size, and charging technique. Current research suggests that a variety of factors influence the loss of efficiency in use including humidity, exposure to certain chemicals, aging, temperature, and etc. While this is true of some charged media, the effect of environmental factors on filtration performance is highly dependent upon the media technology itself. This paper provides an overview of current electret media types detailing media structure and charging techniques. Fundamental impact of environmental factors on filtration performance is presented along with field studies detailing in-use performance of filterers manufactured with charged media.

4

Abd Ali, Safaa Abd Zaid, Aurélie Joubert e Yves Andrès. "Evaluation of Antimicrobial Effect of Zinc Pyrithione against Airborne Fungi and Bacteria Growth Collected onto New and Loaded HVAC Fibrous Filters". Processes 9, n. 9 (27 agosto 2021): 1528. http://dx.doi.org/10.3390/pr9091528.

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Microbial growth onto HVAC filters was observed in real conditions with possible degradation of the indoor air quality. The filtration performance of marketed antimicrobial filters containing zinc pyrithione was tested under laboratory conditions and compared to that of similar filters with the same classification, F7 (EN779:2002). The filtration performance of the two tested filters during loading with PM10 particles was quantified in an experimental setup with filter pressure drop measurement and particle counting upstream and downstream of the filters. The microbial growth on the new and loaded filters, both contaminated with a microbial airborne consortium composed of two bacteria (Gram-positive and -negative) and fungi, was quantified by colony-forming units after conditioning the filters for a few days under controlled temperature (25 °C) and humidity (50% or 90% relative humidity). The results reveal that there was no degradation of the filtration performance of the filters treated with the antimicrobial agent. The efficiency of the antimicrobial treatment, i.e., the ability to inhibit the growth of microorganisms during the incubation period, was significant with the new filters regarding the fungal growth, but the results demonstrate that the antimicrobial treatment became inefficient with the loaded filters.

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Widziewicz-Rzońca, Kamila, e Malwina Tytła. "Water Sorption by Different Types of Filter Media Used for Particulate Matter Collection Under Varying Temperature and Humidity Conditions". International Journal of Environmental Research and Public Health 17, n. 14 (17 luglio 2020): 5180. http://dx.doi.org/10.3390/ijerph17145180.

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The present study describes the effects of temperature and humidity on the level of water absorption by filter blanks most popularly used for gravimetric analyzes of particulate matter (PM) and the effects of those on the accuracy of its weight measurements. The main parts of the research quantified the effect of temperature and humidity conditions on water contents quartz fiber (Q), fiberglass (G), PTFE, and nylon (N) filters. Supplementary studies were conducted to estimate the effects of temperature, humidity and material on mass loss/gain and the shape of water retention. All chemical analyses of water contents were performed by the Karl Fischer titration method. The results indicate that quartz filters are the most susceptible to the variations in water contents under changing humidity levels and therefore, less suitable to high accuracy determinations of PM mass compared to nylon or glass filters; PTFE performed the best due to their hydrophobicity. For PM water contents determinations, the best choice of filter media is PTFE. Although many other factors determine the choice of filter type for PM analyses, the present study is an important contribution to knowledge of assessing the suitability of different types of filter material for specific measurements.

6

Dierkes, M., e U. Hilleringmann. "Telemetric surface acoustic wave sensor for humidity". Advances in Radio Science 1 (5 maggio 2003): 131–33. http://dx.doi.org/10.5194/ars-1-131-2003.

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Abstract. Surface acoustic wave sensors consist of a piezoelectric substrate with metal interdigital transducers (IDT) on top. The acoustic waves are generated on the surface of the substrate by a radio wave, as it is well known in band pass filters. The devices can be used as wireless telemetric sensors for temperature and humidity, transmitting the sensed signal as a shift of the sensor’s resonance frequency.

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Chervinskii, Semyon, Ibrahim Issah, Markus Lahikainen, Alireza R. Rashed, Kim Kuntze, Arri Priimagi e Humeyra Caglayan. "Humidity- and Temperature-Tunable Metal–Hydrogel–Metal Reflective Filters". ACS Applied Materials & Interfaces 13, n. 42 (13 ottobre 2021): 50564–72. http://dx.doi.org/10.1021/acsami.1c15616.

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Chien, Chih-Hsiang, Chufan Zhou, Simon Yang Sing, Benjamin Lopez, Alexandros Theodore, Chang-Yu Wu e Brian K. Birky. "Effects of Relative Humidity on Impregnated Filters Used in Measurement of Airborne Sulfur Dioxide". Annals of Work Exposures and Health 63, n. 7 (6 luglio 2019): 806–13. http://dx.doi.org/10.1093/annweh/wxz053.

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Abstract Impregnated filters treated with alkali and humectant were first used as collection media to assess occupational exposure to sulfur dioxide (SO2), as outlined in the National Institute for Occupational Safety and Health Method 6004 in 1979. Since then, updated treatment protocols have been proposed with decreased amounts of alkali and glycerol, which claim the same filtering capacity. However, there has been no report on how the collection of SO2 on such impregnated media is influenced by relative humidity (RH). This study investigated the role of glycerol (G) amount on impregnated filters (G2 and G10, referring to 2 and 10% glycerol, respectively) in the collection of SO2 (100 l of 10 ppm at 1 l per minute) under low, medium, and high RHs. The testing results show that RH significantly impacted G2 filters with respect to breakthrough time, capacity, and recovery. At low RH, the 5% breakthrough time was less than 10 min and its recovery was merely 42%; at medium and high RHs, although the recovery was satisfactory, the 5% breakthrough time was still less than 100 min. By contrast, G10 filters illustrated nearly 100% recovery and evaluation by analysis of variance showed no significant effect of RH on recovery. In summary, the current treatment protocol of 2% glycerol leads to a significant underestimation of the exposure to SO2 in a low-RH environment; increasing the glycerol content can be an effective alternative to compensating for the effect of RH.

9

Lee, Jinwook, e Jooyoun Kim. "Material Properties Influencing the Charge Decay of Electret Filters and their Impact on Filtration Performance". Polymers 12, n. 3 (24 marzo 2020): 721. http://dx.doi.org/10.3390/polym12030721.

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Electret filters as opposed to mechanical filters display the enhanced ability to capture airborne particles with the electrostatic attraction. However, the environmental aging during shelf-life or use may cancel its benefit by dissipating the charges. This work investigates the polymeric attributes influencing the charge decay and the electrostatic filtration of electret filters, employing polymers with different dielectric constants (εr) and wettability. As accelerated aging, high temperature (120 °C) or high humidity (25 °C, 90% RH) was applied to the electret filters for 48 h. For the humidity aging, wetting property of material was a critical factor affecting the charge decay and the filtration performance, as the absorbed water increases the electrical conductivity. For the thermal aging, the material with the highest εr deteriorated the electric potential and the filtration performance by the largest extent, due to the lower band gap energy for charge transfer. The results of this study implicate that εr and wettability are important material parameters influencing the electric conductivity and chain mobility, and they can be used as convenient predictors for charge retention capacity affecting the robust electrostatic filtration performance.

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Sidheswaran, Meera, Wenhao Chen, Agatha Chang, Robert Miller, Sebastian Cohn, Douglas Sullivan, William J. Fisk, Kazukiyo Kumagai e Hugo Destaillats. "Formaldehyde Emissions from Ventilation Filters Under Different Relative Humidity Conditions". Environmental Science & Technology 47, n. 10 (6 maggio 2013): 5336–43. http://dx.doi.org/10.1021/es400290p.

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ROGOZIŃSKI, TOMASZ, e SERGEI TROFIMOV. "Principles of pulse-jet filters used in the woodworking industry". Annals of WULS, Forestry and Wood Technology 105 (6 giugno 2019): 98–101. http://dx.doi.org/10.5604/01.3001.0013.7724.

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Principles of pulse-jet filters used in the woodworking industry. The pulse-jet filters used to separate wood dust and factors influencing their operation were described in this paper. The analysis of the possibility of the use of pulse-jet filters for wood dust separation presented in this work was based on two basic quantitative criteria. These are the separation efficiency and the pressure drop in the filtration process performed in a dust collector. The influence of wood dust type, filtration velocity and air relative humidity the separation efficiency and the pressure were described.

12

Gryga, Michal, Dalibor Ciprian e Petr Hlubina. "Distributed Bragg Reflectors Employed in Sensors and Filters Based on Cavity-Mode Spectral-Domain Resonances". Sensors 22, n. 10 (10 maggio 2022): 3627. http://dx.doi.org/10.3390/s22103627.

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Spectral-domain resonances for cavities formed by two distributed Bragg reflectors (DBRs) were analyzed theoretically and experimentally. We model the reflectance and transmittance spectra of the cavity at the normal incidence of light when DBRs are represented by a one-dimensional photonic crystal (1DPhC) comprising six bilayers of TiO2/SiO2 with a termination layer of TiO2. Using a new approach based on the reference reflectance, we model the reflectance ratio as a function of both the cavity thickness and its refractive index (RI) and show that narrow dips within the 1DPhC band gap can easily be resolved. We revealed that the sensitivity and figure of merit (FOM) are as high as 610 nm/RIU and 938 RIU−1, respectively. The transmittance spectra include narrow peaks within the 1DPhC band gap and their amplitude and spacing depend on the cavity’s thickness. We experimentally demonstrated the sensitivity to variations of relative humidity (RH) of moist air and FOM as high as 0.156 nm/%RH and 0.047 %RH−1, respectively. In addition, we show that, due to the transmittance spectra, the DBRs with air cavity can be employed as spectral filters, and this is demonstrated for two LED sources for which their spectra are filtered at wavelengths 680 nm and 780 nm, respectively, to widths as narrow as 2.3 nm. The DBR-based resonators, thus, represent an effective alternative to both sensors and optical filters, with advantages including the normal incidence of light and narrow-spectral-width resonances.

13

Joubert, A., J. C. Laborde, L. Bouilloux, S. Callé-Chazelet e D. Thomas. "Influence of Humidity on Clogging of Flat and Pleated HEPA Filters". Aerosol Science and Technology 44, n. 12 (3 novembre 2010): 1065–76. http://dx.doi.org/10.1080/02786826.2010.510154.

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Nordbo, Annika, Pekka Kekäläinen, Erkki Siivola, Ivan Mammarella, Jussi Timonen e Timo Vesala. "Sorption-Caused Attenuation and Delay of Water Vapor Signals in Eddy-Covariance Sampling Tubes and Filters". Journal of Atmospheric and Oceanic Technology 31, n. 12 (1 dicembre 2014): 2629–49. http://dx.doi.org/10.1175/jtech-d-14-00056.1.

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Abstract Adsorption and desorption (together called sorption) processes in sampling tubes and filters of eddy-covariance stations cause attenuation and delay of water vapor signals, leading to an underestimation of water vapor fluxes by tens of percent. The aim of this work was (i) to quantify the effects on sorption in filters and tubes of humidity, flow rate, and dirtiness and (ii) to test a recently introduced sorption model that facilitates correction of fluxes. Laboratory measurements on the transport of water vapor pulses through tubes and filters were carried out, and eddy-covariance field measurements were also used. In the laboratory measurements, the effects of sorption processes were evident, and filters caused a similar attenuation and delay of the signal as tubes. Filters could have a larger impact than a long tube, whereas the flow rate had a much smaller impact on the flux loss than the sorption processes (Reynolds numbers 2120–3360). The sorption model represented well the water vapor pulses in a wide range of conditions. As for the field measurements, the transfer function (TF) derived from the sorption model represented well the observations. Fitting parameters were found to depend strongly on the relative humidity and correlate with the signal delay. Having a more complex shape, TF of the sorption model represented much better the measured TFs than, for example, a Lorentzian or adjusted Gaussian TF, leading on average to a 4% unit difference in the flux corrections. Use of this more complex TF is recommended and its implementation is assisted by the codes provided in appendix B.

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Beliuchenko, Dmytro, Kateryna Tishechkina, Tetiana Hannichenko e Olga Salamatina. "Study of Humidity During Sand Dewatering Using a Cone-Shaped Installation". Key Engineering Materials 953 (25 agosto 2023): 43–51. http://dx.doi.org/10.4028/p-tog6wu.

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The issue of moisture content of sand, which is used in construction as an aggregate for asphalt concrete mixtures, in the production of silicate building materials, roofing roll materials, and various types of glass, is considered. The results of an experimental study of the process of dewatering construction sand samples in conical warehouses under the conditions of using vacuum systems, depending on the time and placement scheme of needle filters, are presented.

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Woo, Myung-Heui, Adam Grippin, Diandra Anwar, Tamara Smith, Chang-Yu Wu e Joseph D. Wander. "Effects of Relative Humidity and Spraying Medium on UV Decontamination of Filters Loaded with Viral Aerosols". Applied and Environmental Microbiology 78, n. 16 (8 giugno 2012): 5781–87. http://dx.doi.org/10.1128/aem.00465-12.

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ABSTRACTAlthough respirators and filters are designed to prevent the spread of pathogenic aerosols, a stockpile shortage is anticipated during the next flu pandemic. Contact transfer and reaerosolization of collected microbes from used respirators are also a concern. An option to address these potential problems is UV irradiation, which inactivates microbes by dimerizing thymine/uracil in nucleic acids. The objective of this study was to determine the effects of transmission mode and environmental conditions on decontamination efficiency by UV. In this study, filters were contaminated by different transmission pathways (droplet and aerosol) using three spraying media (deionized water [DI], beef extract [BE], and artificial saliva [AS]) under different humidity levels (30% [low relative humidity {LRH}], 60% [MRH], and 90% [HRH]). UV irradiation at constant intensity was applied for two time intervals at each relative humidity condition. The highest inactivation efficiency (IE), around 5.8 logs, was seen for DI aerosols containing MS2 on filters at LRH after applying a UV intensity of 1.0 mW/cm2for 30 min. The IE of droplets containing MS2 was lower than that of aerosols containing MS2. Absorption of UV by high water content and shielding of viruses near the center of the aggregate are considered responsible for this trend. Across the different media, IEs in AS and in BE were much lower than in DI for both aerosol and droplet transmission, indicating that solids present in AS and BE exhibited a protective effect. For particles sprayed in a protective medium, RH is not a significant parameter.

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Sýkora, Vlastimil, e Čestmír Hylák. "Dynamická sorpční kapacita malých ochranných filtrů – průmyslové škodliviny". Krízový manažment 20, n. 1 (2021): 23–31. http://dx.doi.org/10.26552/krm.c.2021.1.23-31.

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The aim of the study was to assess the effects of input parameters on the value of dynamic sorption capacity of small protective filters used in the civil protection of the Czech Republic. Relative humidity, the concentration of the test substance/air mixture, type of filter, year of manufacture, batch and type of sorbent, were used as the monitored parameters. The measurements were performed using a gas-air mixture bas ed on cyclohexane, ammonia, sulphur dioxide, chlorine and sulfane. MOF, MOF-2, MOF-4, MOF-5 and MOF-6-M filters were used for the measurements. It has been detected that the tested filters in many cases meet the requirements of the relevant Standard for sorption capacity, namely in cases of cyclohexane, sulfane and sulphur dioxide. It has also been established that MOF-4 filters containing medium-grained sorbent SZS-1000 attained lower values of sorption capacity than filters with CHS-5 sorbent.

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Givehchi, Raheleh, Qinghai Li e Zhongchao Tan. "Filtration of Sub-3.3 nm Tungsten Oxide Particles Using Nanofibrous Filters". Materials 11, n. 8 (25 luglio 2018): 1277. http://dx.doi.org/10.3390/ma11081277.

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This work aims to understand the effects of particle concentration on the filtration of nanoparticles using nanofibrous filters. The filtration efficiencies of triple modal tungsten oxide (WOx) nanoparticles were experimentally determined at three different concentrations for the size range of 0.82–3.3 nm in diameter. All tests were conducted using polyvinyl alcohol (PVA) nano-fibrous filters at an air relative humidity of 2.9%. Results showed that the filtration efficiencies of sub-3.3 nm nanoparticles depended on the upstream particle concentration. The lower the particle concentration was, the higher the filtration efficiency was.

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Khazraei Vizhemehr, Ali, Fariborz Haghighat e Chang-Seo Lee. "Gas-phase filters breakthrough models at low concentration – Effect of relative humidity". Building and Environment 75 (maggio 2014): 1–10. http://dx.doi.org/10.1016/j.buildenv.2014.01.010.

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Jang, Jaehyuck, Kyungnam Kang, Niloufar Raeis‐Hosseini, Aizhan Ismukhanova, Heonyeong Jeong, Chunghwan Jung, Byeongsu Kim, Jung‐Yong Lee, Inkyu Park e Junsuk Rho. "Self‐Powered Humidity Sensor Using Chitosan‐Based Plasmonic Metal–Hydrogel–Metal Filters". Advanced Optical Materials 8, n. 9 (24 febbraio 2020): 1901932. http://dx.doi.org/10.1002/adom.201901932.

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van Popta, A. C., J. J. Steele, S. Tsoi, J. G. C. Veinot, M. J. Brett e J. C. Sit. "Porous Nanostructured Optical Filters Rendered Insensitive to Humidity by Vapor-Phase Functionalization". Advanced Functional Materials 16, n. 10 (4 luglio 2006): 1331–36. http://dx.doi.org/10.1002/adfm.200500899.

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Tago, Yuichiro, Fumie Akimoto, Kuniyuki Kitagawa, Norio Arai, Stuart W. Churchill e Ashwani K. Gupta. "Spectroscopic Measurements of High Emissivity Materials Using Two-Dimensional Two-Color Thermometry". Journal of Engineering for Gas Turbines and Power 127, n. 3 (10 agosto 2004): 472–77. http://dx.doi.org/10.1115/1.1917889.

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Radiative heat transfer characteristics from the surface of a substance coated with a high-emissivity material have been examined from the measured two-dimensional (2D) temperature distribution using two-color thermometry principle. The technique utilized a charge coupled device camera and optical filters having either wide or narrow wavelength bandpass filters. The results obtained were compared to evaluate the accuracy of the temperature measurements. The 2D emissivity distributions were also derived from the measured 2D temperature distributions. The results indicate that the substrate coated with high-emissivity material exhibit high emission of radiation, resulting in effective cooling. The enhanced emissivity of materials also results in improved radiative heat transfer in heating furnaces and other high-temperature applications. The emissivity measured with the wide-bandpass filters increased with temperature. Atmospheric absorption, mainly due to humidity, made a negligible contribution to the total spectral intensity and to the temperature measurements. The small discrepancies are attributed to the dependence of emissivity on wavelength. Thus, the use of narrow-bandpass filters in thermometry is advantageous over the wide-bandpass ones.

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Zhang, Zhaobo, Mahmut S. Ersan, Paul Westerhoff e Pierre Herckes. "Do Surface Charges on Polymeric Filters and Airborne Particles Control the Removal of Nanoscale Aerosols by Polymeric Facial Masks?" Toxics 12, n. 1 (19 dicembre 2023): 3. http://dx.doi.org/10.3390/toxics12010003.

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The emergence of facial masks as a critical health intervention to prevent the spread of airborne disease and protect from occupational nanomaterial exposure highlights the need for fundamental insights into the interaction of nanoparticles (<200 nm) with modern polymeric mask filter materials. While most research focuses on the filtration efficiency of airborne particles by facial masks based on pore sizes, pressure drop, or humidity, only a few studies focus on the importance of aerosol surface charge versus filter surface charge and their role in the net particle filtration efficiency of mask filters. In this study, experiments were conducted to assess mask filter filtration efficiency using positively and negatively charged polystyrene particles (150 nm) as challenge aerosols at varying humidity levels. Commercial masks with surface potential (Ψf) in the range of −10 V to −800 V were measured by an electrostatic voltmeter and used for testing. Results show that the mask filtration efficiency is highly dependent on the mask surface potential as well as the charge on the challenge aerosol, ranging from 60% to 98%. Eliminating the surface charge results in a maximum 43% decrease in filtration efficiency, emphasizing the importance of electrostatic charge interactions during the particle capture process. Moreover, increased humidity can decrease the surface charge on filters, thereby decreasing the mask filtration efficiency. The knowledge gained from this study provides insight into the critical role of electrostatic attraction in nanoparticle capture mechanisms and benefits future occupational and environmental health studies.

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Pavlichenko, Ida, Armin T. Exner, Gennady Logvenov, Giuseppe Scarpa, Paolo Lugli e Bettina V. Lotsch. "Nanomorphology tuning of the thermal response of TiO2/SiO2 Bragg stacks". Canadian Journal of Chemistry 90, n. 12 (dicembre 2012): 1069–77. http://dx.doi.org/10.1139/v2012-081.

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Herein, we present a comparative study of thermo- and environmentally responsive TiO2/SiO2 one-dimensional photonic crystals (Bragg stacks) fabricated by different deposition methods and fabrication schemes, featuring various multilayer nanomorphologies. These include dense multilayer systems processed by physical vapor deposition and wet-chemistry protocols, as well as porous systems, namely, nanoparticle-based optical filters exhibiting textural porosity, and evaporation-induced self-assembled mesoporous Bragg stacks exhibiting predominantly structural porosity, as well as hybrid structures comprising both dense and porous layers. We investigate the spectral shift of the photonic stop band for the different Bragg stack nanomorphologies induced by the humidity-enhanced thermo-optic effect in a temperature range from 15 to 60 °C. We also demonstrate the response and recovery kinetics of the multilayer systems during external changes in ambient humidity. Notably, the choice of fabrication method plays a significant role in the thermal and humidity response of the system. Taking advantage of different material nanomorphologies we can tune the thermal shift of the photonic stop band in the range 0.2–32.9 nm for the Bragg stacks at ambient relative humidity. In addition, we can design dense multilayer systems nonresponsive to humidity and achieve time responses of the porous systems to external changes in humidity ranging from about 1 to 3 s.

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Hsu, Ying-Fang, Chi-Yu Chuang e Shinhao Yang. "Evaluation of the Bioaerosol Inactivation Ability of Chitosan-Coated Antimicrobial Filters". International Journal of Environmental Research and Public Health 18, n. 13 (5 luglio 2021): 7183. http://dx.doi.org/10.3390/ijerph18137183.

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This work considers the enhancement of indoor bioaerosol removal efficiency by liquid coating of the antimicrobial agent chitosan onto polypropylene fibrous filters (CCFs). Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) were chosen as the tested bioaerosols. The results revealed that 2.5% (w/w) of CCFs have significantly higher bioaerosol survival capability (23% and 34% of E. coli and B. subtilis, respectively), compared to an untreated filter (65% and 64% for E. coli and B. subtilis, respectively). Increasing face velocity and relative humidity during operating CCFs could reduce the bioaerosol removal capability. The regression analysis of the experimental findings demonstrated that the higher coating concentration of chitosan had the most positive influence on bioaerosol removal, while the face velocity and relative humidity had a negative influence, but a milder effect was observed (R2 = 0.83 and 0.81 for E. coli and B. subtilis bioaerosols, respectively). A CCF-loaded air-cleaning device was tested in a real indoor environment and resulted in 80.1% bioaerosol removal within 3 h of operating, which suggests that the chitosan-coated filter has the potential for further application in improving indoor air quality in the future.

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Weber, Ines C., Chang-ting Wang e Andreas T. Güntner. "Room-Temperature Catalyst Enables Selective Acetone Sensing". Materials 14, n. 8 (8 aprile 2021): 1839. http://dx.doi.org/10.3390/ma14081839.

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Catalytic packed bed filters ahead of gas sensors can drastically improve their selectivity, a key challenge in medical, food and environmental applications. Yet, such filters require high operation temperatures (usually some hundreds °C) impeding their integration into low-power (e.g., battery-driven) devices. Here, we reveal room-temperature catalytic filters that facilitate highly selective acetone sensing, a breath marker for body fat burn monitoring. Varying the Pt content between 0–10 mol% during flame spray pyrolysis resulted in Al2O3 nanoparticles decorated with Pt/PtOx clusters with predominantly 5–6 nm size, as revealed by X-ray diffraction and electron microscopy. Most importantly, Pt contents above 3 mol% removed up to 100 ppm methanol, isoprene and ethanol completely already at 40 °C and high relative humidity, while acetone was mostly preserved, as confirmed by mass spectrometry. When combined with an inexpensive, chemo-resistive sensor of flame-made Si/WO3, acetone was detected with high selectivity (≥225) over these interferants next to H2, CO, form-/acetaldehyde and 2-propanol. Such catalytic filters do not require additional heating anymore, and thus are attractive for integration into mobile health care devices to monitor, for instance, lifestyle changes in gyms, hospitals or at home.

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Ukagwu, Kelechi John, Azando Isaac Enzoionzi, Val Hyginus Udoka Eze, Chikadibia Kalu Awa Uche e Faith Ukagwu. "Innovative Design and Implementation of Portable and Rechargeable Air Purifier and Humidifier". International Journal of Recent Technology and Applied Science (IJORTAS) 6, n. 1 (29 marzo 2024): 14–24. http://dx.doi.org/10.36079/lamintang.ijortas-0601.618.

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This study presents the innovative design and successful implementation of a Portable and Rechargeable Air Purifier and Humidifier (PRAPH) aimed at addressing indoor air quality issues in Uganda. The device combines air purification and humidification functionalities into a compact, user-friendly, and energy-efficient unit. The design phase of the PRA-PH involved a thorough analysis of existing air purifiers and humidifiers, identifying key limitations such as limited portability, energy inefficiency, and complex maintenance requirements. The system incorporates high-efficiency particulate air (HEPA) filters, activated carbon filters, and ultrasonic humidification technology to effectively remove particulate matter, allergens, and airborne contaminants while simultaneously maintaining optimal humidity levels. A rechargeable lithium-ion battery was integrated to ensure portability, enabling users to use the PRA-PH without relying on a constant power source. Additionally, smart sensors and microcontroller-based control systems were employed to automate the device's operation, adjusting purification and humidification settings based on real-time air quality measurements. The PRA-PH was subjected to rigorous testing to evaluate its efficiency in purifying air and maintaining suitable humidity levels across various indoor environments. The results demonstrated significant improvements in air quality, showcasing the device's ability to effectively remove pollutants and maintain a comfortable humidity range. This study contributes to a portable and rechargeable air purifier and humidifier system that addresses the limitations of existing solutions. The PRA-PH's innovative design, efficient operation, and user-friendly interface make it a promising option for individuals seeking a convenient and effective way to improve indoor air quality and enhance the overall well-being of Ugandans.

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Kendler, Shai, e Asaf Zuck. "The Challenges of Prolonged Gas Sensing in the Modern Urban Environment". Sensors 20, n. 18 (11 settembre 2020): 5189. http://dx.doi.org/10.3390/s20185189.

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The increase in the urban population is impacting the environment in several ways, including air pollution due to emissions from automobiles and industry. The reduction of air pollution requires reliable and detailed information regarding air pollution levels. Broad deployment of sensors can provide such information that, in turn, can be used for the establishment of mitigating and regulating acts. However, a prerequisite of such a deployment strategy is using highly durable sensors. The sensors must be able to operate for long periods of time under severe conditions such as high humidity, solar radiation, and dust. In recent years, there has been an ongoing effort to ruggedize sensors for industrial applications with an emphasis on elevated temperature, humidity, and pressure. Some of these developments are adapted for urban air sensing applications. However, protection from dust is based on filters that have not been modified in the last few decades. Such filters clog over time, thus requiring frequent replacement. This editorial presents the need for a consumable-free dust removal device that provides consistent performance without affecting the sensing process. A specific solution for removing dust using a cyclone dust separator is presented. The cyclone dust separator is implemented as an add-on module to protect commercially available sensors.

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Schwarz, Almuth D., Julian Dutzi, Patrick Weber, Carsten Sattler, Karsten Schulz, Thomas Caesar, Jörg Meyer e Achim Dittler. "Humidity Considerations in Filter Testing Based on Analysis of Filters from Gas Turbine Applications". Chemical Engineering & Technology 45, n. 1 (17 novembre 2021): 43–50. http://dx.doi.org/10.1002/ceat.202100344.

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Montgomery, James F., Sheldon I. Green e Steven N. Rogak. "Impact of Relative Humidity on HVAC Filters Loaded with Hygroscopic and Non-Hygroscopic Particles". Aerosol Science and Technology 49, n. 5 (11 marzo 2015): 322–31. http://dx.doi.org/10.1080/02786826.2015.1026433.

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Godoy, Charlotte, e Dominique Thomas. "Influence of relative humidity on HEPA filters during and after loading with soot particles". Aerosol Science and Technology 54, n. 7 (3 marzo 2020): 790–801. http://dx.doi.org/10.1080/02786826.2020.1726278.

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Düsing, Sebastian, Birgit Wehner, Thomas Müller, Almond Stöcker e Alfred Wiedensohler. "The effect of rapid relative humidity changes on fast filter-based aerosol-particle light-absorption measurements: uncertainties and correction schemes". Atmospheric Measurement Techniques 12, n. 11 (8 novembre 2019): 5879–95. http://dx.doi.org/10.5194/amt-12-5879-2019.

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Abstract. Measuring vertical profiles of the particle light-absorption coefficient by using absorption photometers may face the challenge of fast changes in relative humidity (RH). These absorption photometers determine the particle light-absorption coefficient due to a change in light attenuation through a particle-loaded filter. The filter material, however, takes up or releases water with changing relative humidity (RH in %), thus influencing the light attenuation. A sophisticated set of laboratory experiments was therefore conducted to investigate the effect of fast RH changes (dRH ∕ dt) on the particle light-absorption coefficient (σabs in Mm−1) derived with two absorption photometers. The RH dependence was examined based on different filter types and filter loadings with respect to loading material and areal loading density. The Single Channel Tricolor Absorption Photometer (STAP) relies on quartz-fiber filter, and the microAeth® MA200 is based on a polytetrafluoroethylene (PTFE) filter band. Furthermore, three cases were investigated: clean filters, filters loaded with black carbon (BC), and filters loaded with ammonium sulfate. The filter areal loading densities (ρ*) ranged from 3.1 to 99.6 mg m−2 in the case of the STAP and ammonium sulfate and 1.2 to 37.6 mg m−2 in the case the MA200. Investigating BC-loaded cases, ρBC* was in the range of 2.9 to 43.0 and 1.1 to 16.3 mg m−2 for the STAP and MA200, respectively. Both instruments revealed opposing responses to relative humidity changes (ΔRH) with different magnitudes. The STAP shows a linear dependence on relative humidity changes. The MA200 is characterized by a distinct exponential recovery after its filter was exposed to relative humidity changes. At a wavelength of 624 nm and for the default 60 s running average output, the STAP reveals an absolute change in σabs per absolute change of RH (Δσabs∕ΔRH) of 0.14 Mm−1 %−1 in the clean case, 0.29 Mm−1 %−1 in the case of BC-loaded filters, and 0.21 Mm−1 %−1 in the case filters loaded with ammonium sulfate. The 60 s running average of the particle light-absorption coefficient at 625 nm measured with the MA200 revealed a response of around −0.4 Mm−1 %−1 for all three cases. Whereas the response of the STAP varies over the different loading materials, in contrast, the MA200 was quite stable. The response was, for the STAP, in the range of 0.17 to 0.24 Mm−1 %−1 and, in the case of ammonium sulfate loading and in the BC-loaded case, 0.17 to 0.62 Mm−1 %−1. In the ammonium sulfate case, the minimum response shown by the MA200 was −0.42 with a maximum of −0.36 Mm−1 %−1 and a minimum of −0.42 and maximum −0.37 Mm−1 %−1 in the case of BC. A linear correction function for the STAP was developed here. It is provided by correlating 1 Hz resolved recalculated particle light-absorption coefficients and RH change rates. The linear response is estimated at 10.08 Mm−1 s−1 %−1. A correction approach for the MA200 is also provided; however, the behavior of the MA200 is more complex. Further research and multi-instrument measurements have to be conducted to fully understand the underlying processes, since the correction approach resulted in different correction parameters across various experiments. However, the exponential recovery after the filter of the MA200 experienced a RH change could be reproduced. However, the given correction approach has to be estimated with other RH sensors as well, since each sensor has a different response time. And, for the given correction approaches, the uncertainties could not be estimated, which was mainly due to the response time of the RH sensor. Therefore, we do not recommend using the given approaches. But they point in the right direction, and despite the imperfections, they are useful for at least estimating the measurement uncertainties due to relative humidity changes. Due to our findings, we recommend using an aerosol dryer upstream of absorption photometers to reduce the RH effect significantly. Furthermore, when absorption photometers are used in vertical measurements, the ascending or descending speed through layers of large relative humidity gradients has to be low to minimize the observed RH effect. But this is simply not possible in some scenarios, especially in unmixed layers or clouds. Additionally, recording the RH of the sample stream allows correcting for the bias during post-processing of the data. This data correction leads to reasonable results, according to the given example in this study.

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Henne, Stephan, Wolfgang Junkermann, Josiah M. Kariuki, John Aseyo e Jörg Klausen. "Mount Kenya Global Atmosphere Watch Station (MKN): Installation and Meteorological Characterization". Journal of Applied Meteorology and Climatology 47, n. 11 (1 novembre 2008): 2946–62. http://dx.doi.org/10.1175/2008jamc1834.1.

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Abstract The meteorological conditions at the Mount Kenya (station identifier MKN) tropical Global Atmosphere Watch Programme station are described. Like other stations in mountainous terrain, the site experiences thermally induced wind systems that disturb free tropospheric conditions. Therefore, the adequacy of the site for long-term background atmospheric composition measurements needs to be evaluated. Meteorological parameters for the period June 2002–June 2006 were analyzed, focusing on the development of thermally induced wind systems and boundary layer influence. Filters based on the local wind and day–night differences in specific humidity were developed for selection of times representative of undisturbed free tropospheric conditions. In addition, the convective boundary layer depth was evaluated. Throughout the whole year the station is influenced by thermally induced wind systems and the atmospheric boundary layer. The filters distinguished between thermally and synoptically influenced days. Thermally influenced days (86%) dominated. However, maxima in specific humidity were also reached in the afternoon on synoptically influenced days and were attributed to mixing in the convective boundary layer. During nighttime, downslope wind dominated that carries undisturbed free tropospheric air masses. Nevertheless, during 24% of all nights the specific humidity was also elevated, possibly indicating the presence of residual layers. It is recommended that nighttime data only (2100–0400 UTC) be used for analysis of long-term trends of the free tropospheric background while the remaining data can be used to characterize composition and trends of the regional atmospheric boundary layer. Further exclusion of apparent pollution events and residual layer influence should be considered. With these constraints, the Mount Kenya Global Atmosphere Watch site is adequate for the study of trends and budgets of background atmospheric composition.

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Walter, Stefanie, Peter Schwanzer, Gunter Hagen, Hans-Peter Rabl, Markus Dietrich e Ralf Moos. "Soot Monitoring of Gasoline Particulate Filters Using a Radio-Frequency-Based Sensor". Sensors 23, n. 18 (13 settembre 2023): 7861. http://dx.doi.org/10.3390/s23187861.

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Owing to increasingly stringent emission limits, particulate filters have become mandatory for gasoline-engine vehicles. Monitoring their soot loading is necessary for error-free operation. The state-of-the-art differential pressure sensors suffer from inaccuracies due to small amounts of stored soot combined with exhaust gas conditions that lead to partial regeneration. As an alternative approach, radio-frequency-based (RF) sensors can accurately measure the soot loading, even under these conditions, by detecting soot through its dielectric properties. However, they face a different challenge as their sensitivity may depend on the engine operation conditions during soot formation. In this article, this influence is evaluated in more detail. Various soot samples were generated on an engine test bench. Their dielectric properties were measured using the microwave cavity perturbation (MCP) method and compared with the corresponding sensitivity of the RF sensor determined on a lab test bench. Both showed similar behavior. The values for the soot samples themselves, however, differed significantly from each other. A way to correct for this cross-sensitivity was found in the influence of exhaust gas humidity on the RF sensor, which can be correlated with the engine load. By evaluating this influence during significant humidity changes, such as fuel cuts, it could be used to correct the influence of the engineon the RF sensor.

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Zhao, Wei, Kelimu Tulugan, Xin Zhang, Xiang Li e Peng Tian. "Electrospun 3D Curly Electret Nanofiber Air Filters for Particulate Pollutants". Sustainability 16, n. 7 (28 marzo 2024): 2808. http://dx.doi.org/10.3390/su16072808.

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Amidst rapid industrialization and urbanization, air pollution has emerged as a global environmental challenge. Traditional air filtration materials face challenges in effectively filtering PM0.3 and often result in discomfort due to high air resistance when used for personal protection, as well as excessive energy consumption in industrial air purification applications. This study initially utilized extremely high environmental humidity to induce fiber formation, resulting in the preparation of a fluffy fiber membrane with a three-dimensional curly morphology, which increased the porosity to 96.93%, significantly reducing air resistance during filtration. Subsequently, rutile TiO2 with a high dielectric constant was introduced, exploiting the low pressure drop characteristic of the fluffy 3D curly fiber membrane combined with the electret effect of TiO2 nanoparticles to notably improve the issue of excessive pressure drops while maintaining filtration efficiency. The microstructure, morphology, and element distribution of the fibers were analyzed using FESEM and EDS. FTIR and XRD were employed to examine the functional groups and crystal structure within the fibers. The electret effect and filtration performance of the fiber membrane were investigated using an electrostatic tester and a particulate filtration efficiency tester. The results demonstrated that inducing fiber formation under high-humidity conditions could produce fibers with a 3D curly structure. The fiber membrane was highly fluffy, significantly reducing the pressure drop. Introducing an appropriate amount of titanium dioxide markedly improved the electrostatic effect of the fiber membrane, enhancing the filtration performance of the 3D curly PVDF/TiO2 composite fiber membrane. With a 0.5% addition of TiO2 nanoparticles, the filtration efficiency of the fiber membrane reached approximately 99.197%, with a pressure drop of about 49.83 Pa. This study offers a new approach to developing efficient, low-resistance air filtration materials, showcasing the potential of material innovation in addressing air quality challenges within the sustainable development framework.

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Nunes, Deivid Marques, João Jorge Ribeiro Damasceno e Fábio de Oliveira Arouca. "Analysis of the Collection Efficiency of Fiber Filters on the Filtration of Nano-Sized Particles from Aerosol". Materials Science Forum 802 (dicembre 2014): 297–302. http://dx.doi.org/10.4028/www.scientific.net/msf.802.297.

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Several studies on removal of nanosized particles are being developed with the aim of minimizing the adverse effects nanoaerosols can cause to the environment and human health due to poor air quality. Moreover, scientific and technological studies have developed in the application of nanosized particles. In academy and industry there are many mechanisms to remove nanoparticles from aerosols, such as fiber filters. Thus, this study aims to analyze the performance of fibrous filters, such as polyester filters (porosity is 0.82 and thickness is 2.2 mm and fiber mean diameter of 26 μm. A nanoparticle generator constitutes an atomizer that was used to generate nanoaerosols of monodisperses polystyrene latex) in a size distribution from 20 nm to 200 nm. The performance of the fibrous media was evaluated through the analysis of removal efficiency of nanoaerossols, using a particle counter TSI model 3007 before and after the filtering device. The experimental system consists of a compressor, which generates air current; high efficiency filters, in order to generate ultra-pure air; an atomizer and a container of polystyrene solution to generate aerosol; diffusion dryer to remove silica humidity from the gas stream; a filtration device; and, a counter to particles. The results obtained showed that the efficiency of a filter decreases with increasing filtration rate and diameter in the range in work. The diffusion mechanism is dominant in the separation process.

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Sattenhwaite, Andrew. "The Better Bathroom: A Spiritual and Political Landscape". UnderCurrents: Journal of Critical Environmental Studies 3 (1 aprile 1991): 19–25. http://dx.doi.org/10.25071/2292-4736/37926.

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Imagine this scene: luxuriant broadleaf greenery, ferns and verdant mosses. Perhaps a rock or two poking through. A pool, perhaps with clear water, but obviously deep, and a waterfall, flashing and tumbling, soothing to the ear, and lending the air a tangible humidity. Filtered sunlight dapples the waters.

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MOYER, ERNEST S., e GREGORY A. STEVENS. "“Worst Case” Aerosol Testing Parameters: II. Efficiency Dependence of Commercial Respirator Filters on Humidity Pretreatment". American Industrial Hygiene Association Journal 50, n. 5 (maggio 1989): 265–70. http://dx.doi.org/10.1080/15298668991374624.

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Moyer, Ernest S., e Gregory A. Stevens. "“Worst Case” Aerosol Testing Parameters: II. Efficiency Dependence of Commercial Respirator Filters on Humidity Pretreatment". AIHAJ 50, n. 5 (maggio 1989): 265–70. http://dx.doi.org/10.1202/0002-8894(1989)050<0265:catpie>2.0.co;2.

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Gayo, E., e J. de Frutos. "Interference filters as an enhancement tool for infrared thermography in humidity studies of building elements". Infrared Physics & Technology 38, n. 4 (giugno 1997): 251–58. http://dx.doi.org/10.1016/s1350-4495(97)00025-x.

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Henneken, Hartmut, Martin Vogel e Uwe Karst. "Effects of humidity and filter material on diffusive sampling of isocyanates using reagent-coated filters". Journal of Environmental Monitoring 8, n. 10 (2006): 1014. http://dx.doi.org/10.1039/b607658k.

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Tang, W., T. H. Kuehn e Matt F. Simcik. "Effects of Temperature, Humidity and Air Flow on Fungal Growth Rate on Loaded Ventilation Filters". Journal of Occupational and Environmental Hygiene 12, n. 8 (7 luglio 2015): 525–37. http://dx.doi.org/10.1080/15459624.2015.1019076.

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Joubert, A., J. C. Laborde, L. Bouilloux, S. Chazelet e D. Thomas. "Modelling the pressure drop across HEPA filters during cake filtration in the presence of humidity". Chemical Engineering Journal 166, n. 2 (gennaio 2011): 616–23. http://dx.doi.org/10.1016/j.cej.2010.11.033.

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Xu, Bin, Ya Wu, Zhongping Lin e Zhiqing Chen. "Investigation of Air Humidity Affecting Filtration Efficiency and Pressure Drop of Vehicle Cabin Air Filters". Aerosol and Air Quality Research 14, n. 3 (2014): 1066–73. http://dx.doi.org/10.4209/aaqr.2013.06.0204.

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Huang, Yi Chin, Shin Hao Yang e Chin Hsiang Luo. "Removal Virus Bioaerosols by Filters Pretreated with Chitosan/Surfactant". Advanced Materials Research 214 (febbraio 2011): 163–67. http://dx.doi.org/10.4028/www.scientific.net/amr.214.163.

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This work considers the effects of using the chitosan/sodium dodecyl sulfate (SDS) pretreated filters (CSPFs) as the antiseptic filters on the bioaerosol penetration. Three concentrations of chitosan solutions and chitosan/SDS mixing solutions were used to pretreat the polypropylene fibrous filter to make them antiseptic. The λ virus bioaerosol was generated using a Collison nebulizer, as the challenged bioaerosol. The effects of various factors, including the face velocity and the relative humidity on the bioaerosol collection characteristics were evaluated. Experimental results suggested the pretreatment of chitosan/SDS did have an antiseptic effect on virus bioaerosol and increase the inactivation mechanism. Experimental findings also revealed that the addition pretreatment of SDS did raise the inactivation effect of the chitosan. When adding SDS in the chitosan solution, the ammonium groups could appear and present the antiseptic benefit more obviously. Moreover, the antiseptic of the pretreated filter decreased with face velocity and RH.

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Okrasa, Małgorzata, Jörn Hitz, Aleksandra Nowak, Agnieszka Brochocka, Christoph Thelen e Zbigniew Walczak. "Adsorption Performance of Activated-Carbon-Loaded Nonwoven Filters Used in Filtering Facepiece Respirators". International Journal of Environmental Research and Public Health 16, n. 11 (4 giugno 2019): 1973. http://dx.doi.org/10.3390/ijerph16111973.

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Filtering nonwovens loaded with activated carbon are among the most popular materials used in the construction of filtering facepiece respirators (FFRs) with anti-odour properties that can be used for respiratory protection at workplaces where the occupational exposure limits of harmful substances are not exceeded. Such FFRs, in addition to a polymer filter material of varying effectiveness, also contain a layer of activated-carbon-loaded nonwoven filter, which limits the quantity of chemical compounds entering the breathing zone. The aim of this work was to analyse the influence of challenge concentration (20–120 ppm), relative humidity (2–70%), flow rate (20–55 L/min), and flow pattern (steady-state and pulsating) on the breakthrough of polymer/carbon nonwovens. A commercial activated-carbon-loaded nonwoven filter was used in this study. Its morphology and textural parameters were determined using optical microscopy, image processing, and nitrogen adsorption/desorption measurements at 77 K. Breakthrough experiments were carried out using cyclohexane vapours to assess adsorption characteristics of polymer/carbon media. The results showed that the breakthrough times decreased with increasing challenge concentration (up to 30%), relative humidity (up to 73%), and flow rate (up to 72%). The pulsating flow pattern was found to be more favourable in terms of odour reduction efficiency (up to 30%). The results indicate that all of these factors should be considered during selection and performance assessment of respirators used for odour relief.

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Göbel, Manfred Ulrich, Jürgen U. Keller, Karl Meller, Ingo Schmitz, Thomas Seeger e Eva Schieferstein. "Long-Term Behavior of Fuel Vapor Retaining Systems for Pure (E0) and Blended Fuels (E10) Part 2: Regeneration with Nitrogen of 70% Relative Humidity". Processes 10, n. 2 (18 febbraio 2022): 397. http://dx.doi.org/10.3390/pr10020397.

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In gasoline-driven vehicles, fuel vapor retaining systems are used to prevent the emission of hydrocarbons from the fuel tank into the atmosphere. In this paper, which is Part 2 of our publication, measurements of regeneration processes of the activated carbon by flushing it with humid nitrogen gas of 70% relative humidity are represented. Using purge air with high relative humidities, representing realistic conditions, it can be observed that water is accumulated in the activated carbon. For ethanol-containing fuel blends, additional accumulation of ethanol in the carbon occurs, decreasing the adsorption capacity of the carbon for standard fuel’s components considerably. State-of-the-art testing procedures use purge air with about 50% relative humidity for the regeneration of the activated carbon filters. As this often does not represent real operation conditions, the working limits of the fuel vapor retaining systems could not be identified up to now. Furthermore, the determination of the butane working capacity as a quality parameter of the fuel vapor retaining systems is also based on the assumption of relatively low air humidity. Consequently, a new quality criterion has to be established.

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Lodewyckx, P., L. Fernandez-Velasco e Y. Boutillara. "Estimating the Service Life of Activated Carbon Filters for Air Purification". Eurasian Chemico-Technological Journal 21, n. 3 (30 settembre 2019): 193. http://dx.doi.org/10.18321/ectj860.

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It is very important to be able to predict the breakthrough time of gas mask filters under real life circumstances. This article describes the use of a very simple predictive equation, the Wheeler-Jonas equation, that yields excellent predictions but only within a very restrictive set of boundary conditions. In order to make this model work in a more realistic environment, it has been gradually adapted to take into account a number of parameters related to this environment: a non-constant inlet concentration, a breather flow, new physical forms of activated carbon, the relative humidity and temperature of the ambient air, chemisorbed gases and mixtures of organic vapours. As (nearly) all of these parameters can be calculated independently of each other, based on data that are either readily available or that can be measured, their influence on the complexity of the model stays low. This makes this combined model both easy to use and powerful in predicting breakthrough times of gas mask filters under real-life conditions.

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Nir, Ido, Vladislav Shepelev, Alexander Pevzner, Daniele Marciano, Lilach Rosh, Tal Amitay-Rosen e Hadar Rotter. "Phosphate Additives for Aging Inhibition of Impregnated Activated Carbon against Hazardous Gases". International Journal of Molecular Sciences 24, n. 16 (20 agosto 2023): 13000. http://dx.doi.org/10.3390/ijms241613000.

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Impregnated activated carbons (IACs) used in air filtration gradually lose their efficacy for the chemisorption of noxious gases when exposed to humidity due to impregnated metal deactivation. In order to stabilize IACs against aging, and to prolong the filters’ shelf life, inorganic phosphate compounds (phosphoric acid and its three salts, NaHPO4, Na2HPO4, and Na3PO4) were used as anti-aging additives for two different chromium-free IACs impregnated with copper, zinc, molybdenum, and triethylenediamine (TEDA). Phosphoric acid, monosodium, and disodium phosphate were found to be very efficient in inhibiting the aging of IACs over long periods against cyanogen chloride (the test agent) chemisorption, with the latter being the most efficient. However, the efficiency of phosphate as an anti-aging additive was not well correlated with its ability to inhibit the migration of metal impregnants, especially copper, from the interior to the external surface of carbon granules. Unlike organic additives, the inorganic phosphate additives did not decrease the surface area of the IAC or its physical adsorption capacity for toluene. Using a phosphate additive in IAC used in collective protection and personal filters can improve the safety of the user and the environment and dramatically reduce the need to replace these filters after exposure to humid environments. This has safety, economic, logistical, and environmental advantages.

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Yang, Wenli, e Britt A. Holmén. "Effects of Relative Humidity on Chloroacetanilide and Dinitroaniline Herbicide Desorption from Agricultural PM2.5on Quartz Fiber Filters". Environmental Science & Technology 41, n. 11 (giugno 2007): 3843–49. http://dx.doi.org/10.1021/es062692i.

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