Cabin Air Filters Research Articles

Investigating the filtration performance and service life of vehicle cabin air filters in China

To protect occupants in vehicle cabin environments from the health risks of high concentrations of particulate matter (PM), it is important to install vehicle cabin air filter (VCAF) to eliminate PM. In this study, we investigated the filtration performance of 22 VCAFs. Results showed that the minimum average filtration efficiency was 56.1 % for particles with a diameter of 0.1–0.3 μm, a pressure drop of 33.2–250 Pa at air velocity of 2.5 m/s, and the dust-holding capacity ranged from 5.8 to 19.4 g. In addition, as the filter area increased from 0.23 m2 to 0.50 m2, the filtration efficiency for particles with a diameter of 0.1–0.3 μm increased from 56.7 % to 77.5 %, the pressure drop decreased from 96.1 to 62.5 Pa, and the dust holding capacity increased 2.7 times. Furthermore, we compared the service life of VCAF from 31 major Chinese cities and found that the service life varied greatly from maximum of 1730 h for Haikou to minimum of 352 h for Shijiazhuang. Considering occupant health risks, Beijing requires that VCAFs have PM2.5 filtration efficiency at least 88.1 %, and Liaoning requires minimum of 97.5 %. Hence, choosing the appropriate VCAF based on the atmospheric environment of different cities deserves our attention.

Ensuring the reliability of filtration systems for transport and processing machines by redundancy

The relevance of this study is subordinated to the existing global trend of applying the scientific paradigm of redundancy of individual systems of transport and technological machines. This approach ensures the uninterrupted technological process of crop production following the regulatory reliability indicators. The purpose of this study was to identify failures of subsystems and elements of transport and technological machines depending on the operating time and to ensure reliability by redundancy. The study covered the methodological approaches to the formation of reliability of transport and technological machines. The study analysed the areas of ensuring the reliability of transport and technological machines on the example of machinery and equipment for animal husbandry. Methodical approaches to ensuring the indicators of reliability and maintainability during the operation of a self-propelled mixer were covered. A systematic approach to the self-propelled mixer as a complex transport and technological machine was developed. The principal subsystems that define a self-propelled mixer as a complex transport and technological system were identified. During the study, two groups of failures were identified, which lead to the loss of performance of the research objects. The features of using information and structural redundancy to improve the reliability of filtration systems of self-propelled mixers were presented. The technical condition of the engine air filter should be checked and cleaned after 50 hours, while the cartridge should be replaced after 1000 hours of operation. The functioning of the cabin filtration subsystem is ensured by a condenser, evaporator, desiccant filter, air filter, which should be checked and cleaned every 500 hours, while spare parts should be available in stock for replacement after one year of use. The formed criteria for assessing the technical condition of air filtration systems of a self-propelled mixer will provide a higher level of reliability and expand the list of their parameters. The methodology presented in this study allows increasing the reliability and maintainability of self-propelled mixers, to provide a methodical approach to the formation of reliability of engine air filtration and operator’s cabin air filtration subsystems

Correspondence on "Randomized Cross-Over Study of In-Vehicle Cabin Air Filtration, Air Pollution Exposure, and Acute Changes to Heart Rate Variability, Saliva Cortisol, and Cognitive Function".

Correspondence on "Randomized Cross-Over Study of In-Vehicle Cabin Air Filtration, Air Pollution Exposure, and Acute Changes to Heart Rate Variability, Saliva Cortisol, and Cognitive Function".

In-vehicle exposure to NO2 and PM2.5: A comprehensive assessment of controlling parameters and reduction strategies to minimise personal exposure

Vehicles are the third most occupied microenvironment, other than home and workplace, in developed urban areas. Vehicle cabins are confined spaces where occupants can mitigate their exposure to on-road nitrogen dioxide (NO2) and fine particulate matter (PM2.5) concentrations. Understanding which parameters exert the greatest influence on in-vehicle exposure underpins advice to drivers and vehicle occupants in general. This study assessed the in-vehicle NO2 and PM2.5 levels and developed stepwise general additive mixed models (sGAMM) to investigate comprehensively the combined and individual influences of factors that influence the in-vehicle exposures. The mean in-vehicle levels were 19 ± 18 and 6.4 ± 2.7 μg/m3 for NO2 and PM2.5, respectively. sGAMM model identified significant factors explaining a large fraction of in-vehicle NO2 and PM2.5 variability, R2 = 0.645 and 0.723, respectively. From the model's explained variability on-road air pollution was the most important predictor accounting for 22.3 and 30 % of NO2 and PM2.5 variability, respectively. Vehicle-based predictors included manufacturing year, cabin size, odometer reading, type of cabin filter, ventilation fan speed power, window setting, and use of air recirculation, and together explained 48.7 % and 61.3 % of NO2 and PM2.5 variability, respectively, with 41.4 % and 51.9 %, related to ventilation preference and type of filtration media, respectively. Driving-based parameters included driving speed, traffic conditions, traffic lights, roundabouts, and following high emitters and accounted for 22 and 7.4 % of in-vehicle NO2 and PM2.5 exposure variability, respectively. Vehicle occupants can significantly reduce their in-vehicle exposure by moderating vehicle ventilation settings and by choosing an appropriate cabin air filter.

Characterizing in-cabin air quality and vehicular air filtering performance for passenger cars in China

The rapidly growing vehicle population has become a crucial contributor to severe air-pollution and public health issues. In urban areas, vehicles have become one of the important sources of air pollutants such as nitrogen oxides and fine particulate matter (PM2.5). In particular, the on-road concentrations of traffic-related air pollutants (TRAPs) are typically many times higher than normal ambient concentrations, potentially leading to high in-vehicle exposure levels to TRAPs. Limited studies have focused on the variability in in-vehicle concentrations of TRAPs and linked the pollution level to both out-cabin conditions and the in-cabin filtration performance during real-world travels. Therefore, this study measured on-roadway, in-cabin concentrations of PM2.5 and carbon dioxide (CO2) by using well-calibrated low-cost sensors during various conditions. Our results indicate that, although in-cabin PM2.5 concentrations are correlated to out-cabin PM2.5 concentration levels, the control efficiency would be affected by the ventilation mode and the adoption of vehicular filtration device. The PM2.5 reduction efficiencies could achieve 45% and 77% for in-use and new filters made by vehicle manufacturers respectively, with the average CO2 concentration remained at a safe level (<800 ppm) under the in-vehicle outside air ventilation. The application of a high-efficiency cabin air (HECA) filter can further enhance the PM2.5 filtration efficiency up to 85–96%, indicating the significance of advanced cabin air filtration technology for improving in-cabin air quality and reducing health risk of Chinese drivers.

Development and Performance Evaluation of Polytetrafluoroethylene-Membrane-Based Automotive Cabin Air Filter.

A high-efficiency, long-life cabin filter unit is required for the effective purification of the air inside a vehicle. However, conventional cabin air filters that utilize electrostatic effects are less efficient and less effective owing to environmental factors. Polytetrafluoroethylene (PTFE) membranes exhibit a high porosity and surface-to-surface dust-removal performance, and maintain a stable pressure drop, indicating their good potential as filter materials. Therefore, in this study, the use of PTFE membranes for the fabrication of automobile filters and the filtration performance of the filters were examined. To this end, first, the properties of PTFE membranes mainly used in HEPA air conditioning filters and those of membranes used as vehicle cabin filters were compared. Next, the thickness, weight, stiffness, pore size, and filtration performance characteristics of filter media fabricated by blending melt-blown (MB) nonwoven, PTFE membranes, and supporting nonwoven into a total filtration layer were compared and analyzed. Lastly, the environmental change durability performance of the automobile cabin filter based on PTFE membrane and the results of the test after the installation of the filter in a vehicle were demonstrated.

NO2 levels inside vehicle cabins with pollen and activated carbon filters: A real world targeted intervention to estimate NO2 exposure reduction potential

Traffic related nitrogen dioxide (NO2) poses a serious environmental and health risk factor in the urban environment. Drivers and vehicle occupants in general may have acute exposure to NO2 levels. In order to identify key controllable measures to reduce vehicle occupant's exposure, this study measures NO2 exposure inside ten different vehicles under real world driving conditions and applies a targeted intervention by replacing previously used filters with new standard pollen and new activated carbon cabin filters. The study also evaluates the efficiency of the latter as a function of duration of use. The mean in-vehicle NO2 exposure across the tested vehicles, driving the same route under comparable traffic and ambient air quality conditions, was 50.8 ± 32.7 μg/m3 for the new standard pollen filter tests and 9.2 ± 8.6 μg/m3 for the new activated carbon filter tests. When implementing the new activated carbon filters, overall we observed significant (p < 0.05) reductions by 87 % on average (range 80 - 94.2 %) in the in-vehicle NO2 levels compared to the on-road concentrations. We further found that the activated carbon filter NO2 removal efficiency drops by 6.8 ± 0.6 % per month; showing a faster decay in removal efficiency after the first 6 months of use. These results offer novel insights into how the general population can control and reduce their exposure to traffic related NO2. The use and regular replacement of activated carbon cabin air filters represents a relatively inexpensive method to significantly reduce in-vehicle NO2 exposure.

Impact of activated carbon contents on cabin air filter performance at different fume flow rates

The present study has been undertaken to analyze the filtration performance of two different nonwoven polypropylene filter media, viz. needle felt and spun-bonded sandwiched with granular activated carbon of varying concentration under different face velocities. The materials are studied on a laboratory based cabin air filter test rig. Spun bonded material reveals relatively lower emission and pressure drop. Interestingly, lower face velocity reveals relatively improved filter behavior in case of both the filter materials. Further, a reduction in downstream emission in terms of PM 2.5 &amp; PM 10 , number concentration and peal pressure drop is observed at higher concentration of activated carbon.

Fibrous and granular activated carbon mixed media for effective gas removal as a cabin air filter

Fibrous and granular activated carbon mixed media for effective gas removal as a cabin air filter

Comparison of the service life of an automotive cabin air filter under dust loading conditions of the laboratory environment and on-road driving

Automobile cabin air filters (ACAFs) play an important role in protecting passengers from health risks associated with exposure to high concentrations of particulate matter (PM). Therefore, understanding the filtration mechanism of ACAFs is essential to assessing human exposure to PM. Despite the importance of ACAFs, changes in filter performance over their operation time remain largely uncharacterized; therefore, prediction of the service life of air filters is unreliable. In this study, changes in the performance of ACAFs were analyzed according to operating time under laboratory and on-road driving dust loading conditions. In the laboratory, with constant temperature and humidity, the filtration efficiency increased from 87.5% to 99.1% with increased loading time in the particle size range of 0.3–0.5 μm. This increase occurs as air paths narrow due to the clogging caused by dust, which increases filtration efficiency and causes a pressure drop. However, under on-road driving conditions, filter performance dropped to 58.7% with similar dust loading. These results indicate that dust loading, which is the most widely used variable in service life estimation, is not sufficient to characterize the service life of an ACAF. Therefore, additional studies are needed to evaluate and establish certification parameters and test methods for determining the service life of an ACAF. The present study provides useful baseline information on the lifespan of ACAFs, which will help to improve automotive cabin indoor air quality.

Eco-Friendly Poly(Vinyl Alcohol) Nanofiber-Based Air Filter for Effectively Capturing Particulate Matter

Due to the increasing use of polypropylene-based nonwoven dust masks and air filters, environmental problems that occur due to the plastic pollution resulting from the disposal of these materials have also increased. Hence, an eco-friendly air filter based on PVA nanofibers (NFs) was fabricated by electrospinning on a nonwoven fabric, and its performance was evaluated as a filter capable of blocking or capturing particulate matter. The quality factor of the optimized PVA NF-based air filter was found to be 0.010606 Pa−1, which is lower than that of a HEPA filter (0.015394 Pa−1), but higher than that of a cabin air filter (0.010517 Pa−1) and a dust mask (0.009102 Pa−1). The contamination level of the PVA NF-based filter was analyzed by optical and structural analyses of the filter surface. Finally, the filter was soaked in water to selectively remove the contaminated PVA NF layer, and the remaining nonwoven fabric was able to be reused to make the filter.

Study on Performance of Cabin Air filters Under Different Work Conditions

The in-vehicle air quality has increasingly attracted the attention of people. Hence, air filter performance under actual work conditions demonstrates remarkable significance. It is verified that the electrostatic adsorption can dramatically enhance the fractional efficiency of small-particle pollutants without increasing the pressure loss; as regard a lack of fractional efficiency test on the filter during the whole life cycle in current standards, the paper studied the tendency of filter’s fractional efficiency variation in the whole life cycle and discovered that fractional efficiency of small particles decreased first after increase due to the shielding of electrostatic charge; the tests on different air speed and area of filtered paper were carried out, showing that increasing the area of filtered paper can significantly lower the pressure loss and increase the filtration efficiency, which is of vital significance to provide the reference for further improving the performance of cabin air filter.

Aerosols and SARS-CoV-2: Statement of the "Expert Group Aerosols" on the development, infectivity, spread and reduction of airborne, virus-containing particles in the air

ZusammenfassungAerosole werden gegenwärtig als einer der wesentlichen Übertragungswege für SARS-CoV-2 angesehen, doch ein umfassendes Verständnis der Prozesse und entsprechendes Handeln/Anpassen von Schutzkonzepten erfordert den Austausch von Informationen über interdisziplinäre Grenzen hinweg. Vor diesem Hintergrund hat die baden-württembergische Landesregierung Anfang Oktober 2020 einen multidisziplinären „Expertenkreis Aerosole“ aus Ingenieuren, Naturwissenschaftlern und Medizinern ins Leben gerufen. In seiner Stellungnahme hat der Kreis den aktuellen Kenntnisstand in allen relevanten Fachrichtungen im Kontext der luftübertragenen SARS-CoV-2 Infektion zusammengetragen. Darin wird neben den allseits bekannten Hygiene- und Abstandsregeln die Bedeutung des richtigen Tragens wirksamer Masken hervorgehoben und der Eigen- sowie Fremdschutz verschiedener Masken gegenübergestellt. Weiterhin wird auf die Notwendigkeit des dynamischen und richtigen Lüftens hingewiesen und es werden exemplarisch Lüftungsintervalle und -zeiträume für unterschiedliche Szenarien illustriert. Auf die Wirksamkeit stationärer oder mobiler Innenraumluftfilter als ein wichtiger Baustein im Schutzkonzept wird eingegangen. Die erste Stellungnahme des Expertenkreises macht deutlich, dass die bestehenden Hygiene- und Abstandsregeln (AHA+L) nur in ihrer Kombination und richtig angewandt, den bestmöglichen Schutz vor einer SARS-CoV-2 Infektion bieten.

A Versatile Filter Test System to Assess Removal Efficiency for Viruses in Aerosols

ABSTRACT Mitigation measures to reduce indoor transmission of SARS-CoV-2 and other pathogenic microorganisms are urgently needed to combat the current pandemic and to prevent future airborne epidemics or pandemics. Very efficient exhaust filters for nanoparticles down to sizes of only a few nanometers have been available for many years; they are used, for example, in diesel and, more recently, gasoline vehicles to reduce emissions. The size of soot particles emitted by combustion engines, i.e., primary particles and aggregates, includes those of viruses. Therefore, such particle filters should also efficiently remove viruses. This study aimed to design a filter test system with a controlled airflow allowing to aerosolize particles at the aerosol inlet and collect samples before and after the particle filter. As an example, results obtained for the NanoCleaner®, a filter designed to clean cabin air in vehicles, are presented. Validation with soot particles produced with a CAST soot generator revealed a filter efficiency higher than 99.5%. To assess the relevance of the test filter system to measure efficiency for viral particles removal, MS2 bacteriophages, also called Escherichia virus MS2, were used as virus surrogate and aerosolized into the filter test system with the commercially available Emser nebulizer. Filter efficiencies of more than 99% for MS2 bacteriophages were achieved using the NanoCleaner® in the filter test system. Experiments with ceramic wall-flow filters showed similar results. To enlighten the versatility of the filter test system, a typical aircraft cabin air filter was also characterized. The measurements confirmed the high filter efficiency, and in addition, we show a decrease of bacteriophage’s survival on the filter material over 48 h post-exposure. In conclusion, we have established a versatile system that is modular to test any filter system for the efficiency of eliminating MS2 bacteriophages as virus surrogates from air.

Determinants of ultrafine particles, black carbon, nitrogen dioxide, and carbon monoxide concentrations inside vehicles in the Paris area: PUF-TAXI study.

This study presents real-time concentrations of traffic-related air pollutants during 499 trips conducted by 50 Parisian taxi drivers from PUF-TAXI project. Ultrafine particles (UFP), black carbon (BC), and nitrogen dioxide (NO2 )/carbon monoxide (CO) were measured inside vehicles by Diffusion Size Classifier Miniature® , microAeth® , and Gas-Pro® , respectively, for nine hours. Vehicle/trip data characteristics were collected by questionnaires and on ambient conditions by monitoring stations. The associations between pollutant levels and their potential determinants were analyzed using generalized estimating equation model. Determinants of in-vehicle pollutants levels were identified: (1) ambient factors (meteorology and ambient pollution)-affecting BC, NO2, and CO; (2) vehicle characteristics-affecting all pollutants; and (3) trip-related driving habits-affecting UFP, BC, and CO. We highlight that commuters can, therefore, avoid high in-vehicle air pollutant concentrations mainly by (1) closing windows and activating air-conditioning under air recirculation mode in congested traffic; (2) smooth driving; and (3) maintaining cabin air filters.

Big Data Analysis on the State of Automotive Cabin Air Filters in China

Under the influence of the COVID-19, consumers pay more and more attention to the safety and health of the air in the car. As the core component of the air purification in the car, the performance of the cabin air filter is a hot topic for vehicle enterprises and parts enterprises. This paper introduces the inspection and data analysis of cabin air filter products in China by China Automotive Technology And Research Center, which includes the product geographical distribution, brand compliance rate, the compliance rate of different testing items. Based on the analysis of fractional efficiency of 0.3 μm, 2.5 μm and 10 μm particle sizes and particle sizes distribution in the atmosphere, this paper puts forward the view that it is necessary to pay more attention to the fractional efficiency of particulates which below 1 μm. In addition, the existing problems of cabin air filter are studied by data and its development direction is prospected.

Performance optimization of airliner cabin air filters

This study aims to design a cabin air filter with a high dust loading performance that is suitable for functioning under haze conditions. A longitudinal comparison study was carried out on the initial filtration performance and resistance change rate during the dust holding process of real cabin air filters with different structures (V-shape, Cylinder and Pleat-Plate filters). It was found that the Cylinder filter was better than the other two in terms of the initial quality factor and resistance change rate during operation. Based on the measured data, a calculation model was developed to predict the service life of the filter. The Cylinder filter shows a service life that is 17% longer than that of the V-shape filter. The energy consumption of the Cylinder filter over 6000 flight hours is lower than that of the V-shape and Pleat-Plate filters. Through the flow field analysis based on the filter structure, a preliminary qualitative analysis of the difference in filter performance is provided. For the Cylinder filter, the airflow steering and unique pleat structure enhance the dust holding capacity. We believe that the Cylinder filter is more suitable for areas with a high PM10 concentration in the atmospheric environment, such as China.

Study on Surface Structure of Filter Material of Cabin Air Filter Impacted by Droplets

As the filter material of cabin air filter is closely related to the filtration effect, this paper establishes a physical model of the droplet impact on different surface structures of filter material and numerically simulates dynamic characteristics of the droplet impact on different surface structures. The results show that the ability of filter material to capture droplets is directly proportional to the hydrophilic strength of filter material and the surface roughness (⩽ droplet diameter).

Monitoring the levels of brominated and organophosphate flame retardants in passenger cars: Utilisation of car air filters as active samplers

Filters in residential and office air conditioning (A/C) systems have been used as sampling devices for monitoring different pollutants. However, cabin air filters (CAFs) in the A/C system of passenger cars have not been utilised for this purpose. In this study, we collected 22 used CAFs from passenger cars in Hanoi, Vietnam to analyse for 8 polybrominated diphenyl ethers (PBDEs) and 10 organophosphate esters (OPEs). All the analytes were detected in more than 50% of samples with the exception of BDE153 and BDE154. The average concentrations of ∑10OPEs and ∑8BDEs in the captured dust were 2600 and 40 ng/g, respectively with Tris (1-chloro-2-propyl) phosphate (TCIPP) and BDE209 as the dominant congener in OPE and BDE groups, respectively. CAFs are a potential tool to qualitatively assess the levels of semi-volatile chemicals in suspended dust in cars as a screening step for exposure assessment of those chemicals.

Comparison of filtration performance of commercially available automotive cabin air filters against various airborne pollutants

Controlling air pollutants in the automobile cabin environment has become increasingly important owing to the health risks of exposure to high concentrations of harmful air pollutants. To protect daily commuters and drivers against the harmful effects of air pollution, modern automobiles are commonly equipped with automotive cabin air filters (ACAFs). Thus, understanding the filtration performance of ACAFs is essential for assessing cabin indoor air quality. In this study, six original equipment manufacturer (OEM) and nine after-market ACAFs were selected and their particulate matter (PM) filtration performance against standard particle (ISO 12103-1 A2 dust), filter pressure drop under various airflow velocities, and gas removal performance against standard test gases (n-butane and toluene) were estimated. In the PM filtration test, the lowest filtration performance occurred at a particle size range of 0.3–0.5 μm, with a filtration efficiency of 50–90%, and the filtration performance increased with increasing particle size. The PM filtration performance of OEM ACAFs (72.3 ± 13.81%) was higher than that of after-market ACAFs (56.4 ± 23.72%). All test OEM ACAFs satisfied the Korea Air Cleaning Association standard filtration performance guidelines for 0.3–0.5-μm particles (>50%), but four of the nine after-market ACAFs did not satisfy the standard guidelines. In addition, only one of the six OEM ACAFs simultaneously satisfied the standard removal performance guidelines for n-butane (>70% after 1 min and >45% after 5 min) and toluene (>80% after 1 min and >70% after 5 min). This study provides valuable baseline information on ACAFs for understanding and improving cabin indoor air quality.