Particle Filtration Efficiency Research Articles

Aerosol deposition on face masks in an open environment during inhalation

The aerodynamics of aerosols and their deposition on face masks play a critical role in determining the effectiveness of respiratory protection. While existing studies have focused on the risks associated with aerosol dispersion during exhalation, little attention has been paid to aerosol aerodynamics in an open environment, where aerosols can circumvent masks, during inhalation. This is because mask performance has primarily been evaluated by the particle filtration efficiency in closed pipe setups, which do not account for the aerodynamics of aerosols around the wearer's face. In this study, we conduct experiments in an open environment to investigate the aerosol flow around a face mask and the aerosol deposition under varying inhalation pressures. Our results indicate that an aerosol flow near a mask surface behaves like a viscous flow, stagnating within the range of human inhalation. Within this range, we find that the amount of aerosol deposited can be predicted by modifying existing aerodynamics theory. Using a theoretical model, a critical inhalation pressure is identified at which water aerosols begin to penetrate through a mask. Finally, we propose the aerosol circumvention efficiency as a new metric to assess mask performance in open environments by taking into account the effects of aerosol circumvention.

3D Porous Nanocellulose Based Filter from Palm Bunch Using Tert‐Butyl Alcohol‐Assisted Pore Inducive Technique for Airborne Particulate Matter Retention

AbstractEnvironmental hazards, especially particulates, and microbiological pollutants, have resulted in significant negative impacts on human health. In this study, 3D biodegradable cellulose filters were made from nanocellulose and tested for the removal efficiency of airborne particulates. Cellulose was first extracted from palm empty fruit bunches (EFBs) using green Deep Eutectic Solvents (DESs) under moderate temperature and then homogenized at high pressure to produce cellulose at the nanoscale size. Three types of renewable choline chloride (ChCl)‐based DESs were used: lactic acid, 1,3‐butanediol, and oxalic acid. The maximum cellulose yield from DES pretreatment was 38.78 % based on raw EFB (100 % cellulose yield based on cellulose in EFB) with ChBu60 C and the maximum nanocellulose yield was 68.49 % based on cellulose in EFB with ChLa80 C after 12‐pass high pressure homogenization. The cellulose air filter was fabricated using tert‐butyl alcohol (tBuOH) solvent exchanged under freeze‐drying conditions and characterized by different state‐of‐the‐art techniques. It was shown that the ChBu80 C filter had the lowest pressure drop (10.16 mmH2O or 2.07 mmH2O cm−2) and the maximum particle filtration efficiency (32.51 % for 0.1 μm and 93.63 % for 1.0 μm particles). The process simulation and techno‐economic analysis were performed for nanocellulose production and air filter fabrication to select the most feasible technology.

Development of Multi-Walled Carbon Nanotube-Integrated Recycled Polyethylene Terephthalate Electrospun Antibacterial Face Mask

In this study, electrospun nanofiber membranes were successfully fabricated by modifying recycled polyethylene terephthalate (r-PET) with multi-walled carbon nanotubes (MWCNTs) for face mask applications. The recycling of PET bottles ensures effective waste management, while the electrospinning process facilitates the creation of delicate nano-range fibers. The inclusion of MWCNTs aimed to assess the antibacterial activity of the resulting nanomembranes. The fabricated samples underwent comprehensive characterization, including scanning electron microscopy (SEM), ultimate tensile testing, particulate filtration efficiency (PFE) testing, Fourier transform infrared spectroscopy (FTIR), and antibacterial sensitivity assays, revealing significant findings. MWCNTs incorporation led to minor bead formation in the membranes, with fiber diameters ranging from 446 to 862 nm. However, MWCNTs resulted in reduced stiffness and tensile properties due to the disruption of polymer chain alignment. The nanofiber membranes demonstrated effective filtration of 0.3 µm particulates, achieving filtration rates between 96 to 97%Functional group analysis confirmed the presence of both r-PET and MWCNTs in the composites. Although the r-PET/MWCNTs 12 kV membrane lacked an antibacterial zone of inhibition, it exhibited reductions of 28.64% for S. aureus and 31.9% for E. coli. These results collectively underscore the potential of r-PET/MWCNTs samples as an alternative nanofibrous membrane material for face masks. J. of Sci. and Tech. Res. 5(1): 63-74, 2023

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.

Engineering nano-thin electrospun coatings for air filters with high filtration and breathability by nanofiber charge control

A modified electrospinning design was introduced to overcome the limitation in non-uniformity of the nanofibrous coating on the surface of non-conducting, statically charged polypropylene microfibers. By manipulating the charge distribution over the non-conducting surface via variations in the polarity of the Taylor cone and the electrospinning geometry, it was possible to obtain a uniformly adherent and thin nanofibrous coating over a large area to achieve a layer-by-layer simultaneous deposition of + ve and −ve fibers onto a non-conducting membrane. The uniformity and quality of this nanocoating was found to have a direct effect on particle filtration and breathability of air filters. The filter showed a high particle filtration efficiency of 96 % for 0.3 µm particles, with excellent breathability.

The Effect of the Size of SUS316L Flake Powder on the Characteristics of Metal Powder Filt ers with a Double-Layered Pore Structure Fabricated by the WPS Process

When fabricating a metal powder filter with a double-layered pore structure, which includes a microporous layer, by coating flake-shaped powder using the Wet Powder Spray (WPS) process, it is crucial to ensure that the coating is applied parallel to the surface of the metal powder filter. Failure to do so can result in a non-uniform pore structure, leading to a rapid decline in particle filtration efficiency. Therefore, it is necessary to improve the alignment of the coated flake-shaped powder on the filter surface. In this study, a metal powder filter with a double-layered pore structure was fabricated by applying a flake-shaped metal powder coating to a tube-shaped SUS316L powder filter using the WPS process. In order to improve the flake-shaped powder orientation of coating layer, the impact of the rolling process was investigated. The characteristics of the pores were analyzed based on the powder size and the rolling time. The microstructure of the fabricated metal powder filter was observed using an optical microscope, surface roughness, variations in thickness, and air permeability were analysed.

Numerical study on the filtration characteristics of fine particles in granular bed filter at high temperature

Granular bed filter (GBF) has become one of the current research hot topics due to its excellent performance in removing fine particles. In this paper, a three-dimensional fixed bed GBF filtration model was established and its accuracy was verified. Then, the GBF filtration performance at high temperature were studied. The results demonstrate that elevating the temperature diminishes the filtration efficiency, albeit to a limited extent. The increasing of inlet gas velocity can significantly improve pressure drop for GBF and the filtration efficiency for fine particles of sizes larger than 5 μm. As the diameter of stacked granular particle diameter grows, the filtration efficiency and pressure drop drops. The density of fine particles almost does not affect the filtration efficiency for fine particles of 1∼7 μm, but a higher density leads to a higher filtration efficiency for fine particles of sizes bigger than 9 μm. Additionally, as the fine particles size increases, the change of the filtration efficiency roughly goes through three stages: Stage 1: the filtration efficiency is basically unchanged; Stage 2: the filtration efficiency increases rapidly; Stage 3: the filtration efficiency increases steadily, but the rate of increase slows down. With the increase of the fine particles Stokes number, the filtration efficiency of GBF will pass through two phases of stabilization and rapid increase.

Hybrid structured silk-rPET nanotechnical cloth for advanced air purification

AbstractAir pollution has become a significant global issue due to its detrimental environmental and human health effects. In this study, a novel approach was taken to address these challenges by developing a recycled polyethylene terephthalate (rPET) nano-coated silk technical cloth embedded with green-synthesized silver nanoparticles (AgNPs) using a solution electrospinning technique. The filtration performance of the developed material was assessed through particle filtration efficiency (PFE) tests, while differential pressure (DP) tests were conducted to evaluate pressure drop. SEM, FTIR, tensile, antibacterial, radiative heat barrier performance, and moisture management properties of the developed samples were also performed. Maximum 96.58% of filtration performance was observed with corresponding low differential pressures of 29.1 Pa/cm2; maximum tensile force and elongation% were 157.47 N and 15.32%, respectively of the developed samples. FTIR analysis confirmed the presence of silk, rPET, sodium alginate, and AgNPs in the developed sample. Antibacterial assays demonstrated inhibition against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Moisture management property revealed water penetration resistance and radiative heat barrier testing showed good barrier performance. These results make the promising potential of the developed material as an advanced air filter. Graphical Abstract

Coaxial electrospun PVA-SAP functional nanofibers embedded with betel leaf extract for enhanced germicidal activity and breathability

This study investigates the formation of coaxial electrospun nanofibrous membrane with enhanced germicidal activity and breathability using superabsorbent polymer and polyvinyl alcohol integrated with betel leaf extract and its utilization for developing performance textiles. The functional nanofibrous membrane was fabricated through the coaxial electrospinning technique and characterized for the intended applications. The morphological investigation of the developed nano-membrane using scanning electron microscopy revealed the formation of regular nanofibers with diameters ranging from 154 to 200 nm. The FTIR spectra suggested the existence of functional compounds in the nanofibers from their characteristic peaks. The presence of the bioactive compounds in the ethanolic extract of betel leaf was explored using phytochemical screening. The analysis of antibacterial activity against S. aureus and E.coli using the agar disc diffusion method showed an enhanced zone of inhibition with a maximum dimension of 27 mm and 24 mm against S. aureus and E.coli, respectively. The developed coaxial nanofibrous membranes also demonstrated acceptable particle barrier performance with greater than 95 % efficiency and a superior tensile strength of 99.5 N. Besides, the improved moisture management and air permeability of coaxial nano-membranes embedded with betel leaf extracts suggested an easy transfer of fluid and moisture vapor from the body to the environment via the membrane. Hence, the improved germicidal activity with acceptable particle filtration efficiency and enhanced breathability of the developed coaxial electrospun nano-membranes indicated their potentiality of utilizing them in designing performance textiles with simultaneous barrier performance and breathability for comfort.

Photo-responsive polypropylene/zinc oxide/polydopamine-TEMPO composite membranes with light-induced self-sterilization

Face masks play a pivotal role in preventing infection transmission. However, the capture of infection-sourced particles in face masks poses challenges related to reuse, necessitating proper disposal. We developed a self-sterilizable polypropylene-based membrane for face masks to address challenges associated with infection transmission prevention. The membrane, created using 3D printing, underwent functionalization with zinc oxide (ZnO) and polydopamine (PDA)-TEMPO to achieve broad-spectrum light absorption and facilitate self-sterilization through photocatalytic and photothermal effects upon light exposure. The hydrophobic surface (water contact angle: 133 ± 2 °) minimized moisture accumulation, and the membrane exhibited robust mechanical properties, including shear strength (1.25 ± 0.5 kPa) and peel resistance strength (112.8 ± 11.2 kPa). The evaluation demonstrated stability in airflow (0 to 500 cm3/s) and excellent aerosol filtration efficiency (94.8 ± 0.6 %) for particles (PM 0.3, PM 2.5, PM 10), comparable to commercial masks. The membrane showed antibacterial efficacy over five uses in a simulated respiratory environment. Safety assessments confirmed biocompatibility through cytocompatibility and skin irritation assays. In conclusion, this membrane offers efficient filtration and photo-triggered sterilization, presenting a promising solution for next-generation face masks to address concerns related to reuse, disposal, and infection control.

Electrospun 3D Curly Electret Nanofiber Air Filters for Particulate Pollutants

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.

Effects of yarn properties on aerosol filtration performance of single jersey fabrics

A pandemic caused by airborne pathogens raises a great need for N95 respirators and surgical masks. Subsequently, the risk of undersupply becomes a primary challenge requiring the prioritization of those masks for healthcare workers. Health agencies recommend wearing cloth masks in low-risk groups to reduce the demand. Unlike N95 respirators and surgical masks, cloth masks can be made from various fabrics, and their filtration performance becomes material-dependent. However, the existing literature presents limited and contradictory results on the property-performance relationship of fabrics used for cloth masks. Thus, the fundamental parameters determining the effectiveness of the fabrics remain unknown. Herein, we investigated the effects of yarn properties and multilayering on the filtration performance of single jersey fabrics. The fabrics performed up to 45% particle filtration efficiency, with the range of air permeability from 110–330 ft3/min/ft2. The results revealed that while the structural differences associated with the yarn choice had a smaller impact on the particle filtration efficiency of the fabrics compared to air permeability, their effects were great enough to yield statistically significant differences between the fabrics. In addition, our findings demonstrated that multilayering effectively improved the filtration performance of fabrics but resulted in a greater increase in airflow resistance than particle filtration efficiency. To limit the tradeoff between air permeability and particle filtration efficiency, yarn properties should be considered in the material selection of multilayer masks. We anticipate that our work will be a starting point for a guide on cloth masks with minimal filtration and breathability requirements.

Comparison of in situ and padding method to incorporate Green synthesized AgNPs by using Calendula arvensis into nonwoven fabrics

Nonwoven fabrics are the primary source of disposable medical clothing, which cause a huge medical waste. One possible way to reuse this disposable clothing is through antibacterial treatment. Among various metal nanoparticles, silver nanoparticles (AgNPs) are preferable regarding ecology and human health. Green synthesis is an ecological alternative to synthesize AgNPs from silver nitrate (AgNO3) solution. The silver nanoparticles (AgNPs) were successfully synthesized from Calendula arvensis extract and AgNO3 at a certain temperature and incorporated into the fabric by padding and in-situ method. The pretreatments applied to the nonwoven fabric were found very important in terms of providing antibacterial activity. AgNPs applied according to the in situ method could provide 99% antibacterial activity on nonwoven surface fabrics. The samples treated by AgNPs with the in situ method performed better for both particle filtration efficiency (PFE) and bacterial filtration efficiency (BFE) than the samples treated with the padding method.

Influence of Electrospinning Parameters on the Morphology of Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Fibrous Membranes and Their Application as Potential Air Filtration Materials.

A large number of non-degradable materials have severely damaged the ecological environment. Now, people are increasingly pursuing the use of environmentally friendly materials to replace traditional chemical materials. Polyhydroxyalkonates (PHAs) are receiving increasing attention because of the unique biodegradability and biocompatibility they offer. However, the applications of PHAs are still limited due to high production costs and insufficient study. This project examines the optimal electrospinning parameters for the production of PHA-based fibrous membranes for air filtration. A common biodegradable polyester, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), was electrospun into a nanofibrous membrane with a well-controlled surface microstructure. In order to produce smooth, bead-free fibers with micron-scale diameters, the effect of the process parameters (applied electric field, solution flow rate, inner diameter of hollow needle, and polymer concentration) on the electrospun fiber microstructure was optimized. The well-defined fibrous structure was optimized at an applied electric field of 20 kV, flow rate of 0.5 mL/h, solution concentration of 12 wt.%, and needle inner diameter of 0.21 mm. The morphology of the electrospun PHBV fibrous membrane was observed by scanning electron microscopy (SEM). Fourier transform infrared (FTIR) and Raman spectroscopy were used to explore the chemical signatures and phases of the electrospun PHBV nanofiber. The ball burst strength (BBS) was measured to assess the mechanical strength of the membrane. The small pore size of the nanofiber membranes ensured they had good application prospects in the field of air filtration. The particle filtration efficiency (PFE) of the optimized electrospun PHBV fibrous membrane was above 98% at standard atmospheric pressure.

Nitrogen and sulfur doped carbon dots coupled cellulose nanofibers: A surface functionalized nanocellulose membranes for air filtration

BackgroundThe current study demonstrates a process to produce a hybrid bio-organic cellulose nanofiber (CNF) membrane with high filtration performance and mechanical strength. This was accomplished by 1) tailoring the functional groups of CNFs, notably using the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical oxidation and 2) coupling them with carbon dots (CDs). MethodsThe surface chemistry of CNF was modified through TEMPO oxidation. Subsequently, a coupling reaction was conducted with CDs synthesized hydrothermally, as well as synthesized N/S-CDs derived from palm bunch. The impact of these modifications on the formation of air filters was investigated. Modification and coupling of surface modified CNF were evaluated by advanced analytical techniques. The toxicity of pristine and N/S-CDs coupled cellulose nanofibers was studied by cytotoxicity assay. Vacuum filtration and sequential compression molding techniques were applied to fabricate CNF filters, and the particle filtration efficiency of different filters was determined. Significant findingsThe coupling of N/S-CDs to CNF significantly enhanced the tensile strength of the membranes. Coupling of N/S-CDs to TEMPOCNF membrane showed the highest tensile strength (9.3 ± 1.9 MPa), while N/S-CDs coupling to CNF membrane exhibited slightly lower tensile strength (9.0 ± 1.3 MPa). The average pore diameter of the filters was slightly reduced after the CNF surface modification, which led to higher differential pressure across the filters. Both the pristine and TEMPO-modified CNF filters displayed high filtration efficiency for 0.3 μm-aerosol particles (∼70–81 %) and 0.1 μm-aerosol model particles (∼50–68 %), which was in a range of bacteria and viruses. This study provided detailed information about the fabrication of modified CNF filters with high air filtration efficiency for micro/nano-sized particles using cost-effective biodegradable raw materials.

Particle Filtration Efficiency, Breathability, and Reusability of Common Masks

Particle Filtration Efficiency, Breathability, and Reusability of Common Masks

Engineering surgical face masks with photothermal and photodynamic plasmonic nanostructures for enhancing filtration and on-demand pathogen eradication.

The shortage of face masks and the lack of antipathogenic functions has been significant since the recent pandemic's inception. Moreover, the disposal of an enormous number of contaminated face masks not only carries a significant environmental impact but also escalates the risk of cross-contamination. This study proposes a strategy to upgrade available surgical masks into antibacterial masks with enhanced particle and bacterial filtration. Plasmonic nanoparticles can provide photodynamic and photothermal functionalities for surgical masks. For this purpose, gold nanorods act as on-demand agents to eliminate pathogens on the surface of the masks upon near-infrared light irradiation. Additionally, the modified masks are furnished with polymer electrospun nanofibrous layers. These electrospun layers can enhance the particle and bacterial filtration efficiency, not at the cost of the pressure drop of the mask. Consequently, fabricating these prototype masks could be a practical approach to upgrading the available masks to alleviate the environmental toll of disposable face masks.

Do Surface Charges on Polymeric Filters and Airborne Particles Control the Removal of Nanoscale Aerosols by Polymeric Facial Masks?

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.

Selenium nanoparticles incorporated in nanofibers media eliminate H1N1 activity: a novel approach for virucidal antiviral and antibacterial respiratory mask.

The consecutive viral infectious outbreaks impose severe complications on public health besides the economic burden which led to great interest in antiviral personal protective equipment (PPE). Nanofiber-based respiratory mask has been introduced as a significant barrier to eliminate the airborne transmission from aerosols toward reduction the viral infection spreading. Herein, selenium nanoparticles incorporated in polyamide 6 nanofibers coated on spunbond nonwoven were synthesized via electrospinning technique (PA6@SeNPs), with an average diameter of 180 ± 2 nm. The nanofiber-coated media were tested for 0.3 μm particulate filtration efficiency based on Standard NIOSH (42 CFR 84). PA6@SeNPs had a pressure drop of 45 ± 2 Pa and particulate filtration efficiency of more than 97.33 which is comparable to the N95 respiratory mask. The bacterial killing efficiency of these nanofibers was 91.25% and 16.67% against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively. Furthermore, the virucidal antiviral test for H1N1 infected Madin-Darby Canine Kidney cells (MDCK) exhibited TCID50 of 108.13, 105.88, and 105.5 for 2, 10, and 120 min of exposure times in comparison with 108.5, 107.5, and 106.5 in PA6 nanofibers as control sample. MTT assay indicated excellent biocompatibility of electrospun PA6@SeNP nanofibers on L292 cells. These results propose the PA6@SeNP nanofibers have a high potential to be used as an efficient layer in respiratory masks for protection against respiratory pathogens.

An assessment of the application of catalyst preheating prior to engine cold start to improve the filtration performance of CDPF on particulate emissions

The catalytic diesel particulate filter (CDPF) is an effective technology for reducing particle emissions. However, during engine startup, especially in cold start conditions, notable particle emissions are observed at the CDPF outlet. These emissions are attributed to combustion deterioration during startup and the low temperature of the aftertreatment catalyst. Addressing this challenge, this study investigated the effectiveness of rapidly preheating the diesel oxidation catalyst (DOC) and CDPF substrate temperatures before engine start to enhance particle removal during cold starts. Experimental results indicated that CDPF filtration efficiency during cold start was lower compared to hot start conditions, with a clean CDPF exhibiting very low efficiency due to minimal particle deposition. Substrate temperature preheating of either the DOC or CDPF was found to improve CDPF filtration efficiency for particles during cold start, albeit with a concurrent increase in emissions of particles smaller than 50 nm. Notably, a combination of a 250 °C DOC with a 22 °C CDPF yielded the most significant reduction in particle emissions, particularly for particles under 50 nm. Given that the DOC shares the same material composition as the CDPF but has a smaller volume that requires less energy for heating, preheating the DOC emerges as a more energy-efficient strategy. These findings underscore the need for more comprehensive studies on catalyst preheating to further the commercialization of technologies that effectively reduce cold start particle emissions, aligning with increasingly stringent future emission regulations.