Aspiration Efficiency Research Articles

Accelerated gastric emptying is associated with improved aspiration efficiency in obesity

BackgroundThe overall effectiveness of aspiration therapy (AT) for obesity relies on optimal aspiration timing after a meal, which can vary depending on a patient’s rate of gastric emptying (GE). Our...

РОЗРОБКА ЗАХОДІВ ПОКРАЩЕННЯ УМОВ ПРАЦІ ПРИ ВИРОБНИЦТВІ ЧАВУНУ

The article explores the causes of working environment pollution and identifies the sources of harmful and dangerous emissions in pig iron production, along with searching for rational measures to improve the blast furnace cast house aspiration system efficiency to remove toxic gases, dust and exhaust heat. A mathematical modeling methodology for transfer process of molten iron and slag from the blast furnace to the ladle has been employed. The best practice from Zaporizhstal Steel Works on a new aspiration system at blast furnace casting yard laid the basis for the research. An aerodynamic calculation method was used to detect deficiencies in the aspiration system. Statistical method to validate the results obtained was used for constructing of graphs and nomograms. The major causes of inefficiency of the current system of covering iron and slag troughs of a blast furnace casting yard have been revealed, in particular the bypass channel for slag from the main drain trough for molten iron and high local resistance losses on iron and slag distribution (the skimmers). Total and local resistance losses in various areas of drain gutters and aspiration systems have been calculated along with estimating the locations for additional exhaust hood installation, i.e. the special zones for skimmers, the main, transfer and bypass troughs for cast iron and slag. It is proved that by increasing the aspiration efficiency contamination of the working area is reduced, thus improving labour conditions significantly. It is proposed to use modern heat-resistant concrete troughs with higher resistance and longer life service. The proposed modification of trough slabs will facilitate their replacement when carrying out repair works on trough lining and cleaning. An aspiration system model for a typical blast furnace cast house has been developed and explored. The areas and reasons behind the loss of resistance in the exhaust system of hood covering for molten iron and slag troughs are identified. Recommendations to enhance the system efficiency to reduce contamination of the working environment and improve working conditions have been suggested.

Preferred sampler inlet configurations for collection of aerosolized nano-scale materials

Due to the lack of standard industrial hygiene sampling protocols for collection of nano-scale materials, sampling inlet device selection is left to individual researchers and professionals. The objective of this study was to compare nano-scale aspiration efficiency for common inlet configurations with that of an open-ended sampler tube that is a commonly used inlet for direct reading instruments such as a condensation particle counter. A polydisperse aerosol was generated using an electric motor as the aerosol source. Typical aerosols generated by this method produced particles with geometric mean mobility diameters of approximately 30nm with geometric standard deviations of approximately 2. Comparison of raw particle counts in size ranges measured with a scanning mobility particle analyzer was made by determining the fractional difference between the selected inlet and that of the open-ended tube. Particle size distributions were nearly identical for all inlet types. The same held true for numbers of particles collected with the exception that the needle inlet was highly variable. When completing air monitoring for nano-scale materials, inlets on most collection devices (filters, tubing) do not impact aspiration efficiency. This means that it is not necessary to match inlet configurations when using multiple methods to collect and analyze nano-scale materials.

Reducing energy consumption and increasing filter life in HVAC systems using an aspiration efficiency reducer: Long-term performance assessment at full-scale

The concept of using an aspiration efficiency reducer (AER) in building heating ventilation and air conditioning (HVAC) systems to control particulate air pollution concentrations was previously demonstrated using a 1:4 scale experimental device. The AER acted as a passive form of air pollution control and reduced the particulate loading rate on filters in HVAC systems, thus reducing fan energy consumption. This paper discusses the design considerations that were accounted for in developing a full-scale AER device during a long-term performance assessment. A field assessment of a new full-scale AER device was performed at an urban commercial building in Dublin, Ireland. The results from two air handling units (AHUs), one Control-AHU and one AER-AHU (with an attached AER device), allowed for a comparison of energy consumption and filter lifespans. Particulate matter (PM) and energy consumption in both AHUs were monitored over time for each AER design. The full-scale AER device reduced PM concentration entering the HVAC system by 34% over the operational life cycle of a filter, reducing energy consumption by up to 14%. Alternatively the AER could be used to extend the lifespan of a filter by 75%. The size distribution of PM deposited on the AER and Control filters established that the device was more effective for coarser particles. Energy and filter savings can be achieved using this passive technique, which can translate to environmental, resource and economic savings in the building HVAC sector.

Effect of turbulent thermal plume on aspiration efficiency of micro-particles

Evaluating the potential health risks from exposure to the air contaminants and evaluating the inhalability of micro-particles through the human nose or mouth is a crucial subject in designing ventilation systems. Using a realistic human body with detailed facial features, the effects of turbulent airflow field generated by the human thermal plume on the aspiration efficiency of the nasal airway for different ambient conditions were investigated. For the rest breathing rate of 7.5 l/min, the airflow was first simulationed by solving the mean continuity, momentum and energy equations using the RNG k-ε turbulence model for the buoyancy-driven flow around the heated mannequin. Then a continuous random walk (CRW) stochastic model utilizing the normalized Langevin equation was used to investigate the effect of turbulence fluctuations on particle trajectories released in the domain around the mannequin. Particular attention was given to the aspiration of the inhaled micro-particles under various conditions. In addition to the common case that the body temperature is higher than the ambient condition, the special case that the situation is reversed is also studied. The simulations results showed that the thermal plume around the human body and stochastic behavior of particles due to turbulence significantly affect the aspiration of inhaled particles through nostrils.

Numerical investigation of boundary layer suction on certain highly loaded aspirated compressor at low speeds

Boundary layer suction is considered to be an available approach to restraining or even eliminating flow separation and to improve the aerodynamic performance of the compressor. In this paper, a highly loaded axial-flow aspirated compressor based on a low-reaction design concept is investigated in detail to find an appropriate flow control strategy for boundary layer suction to achieve significant performance benefit. The flow control strategy consists mainly of the arrangement of suction hole and the aspirated flow rate. The geometrical models including aspiration cannulas, stator cavity and aspiration channel are novelly applied in this research to approach a real engineering application. Complete compressor maps are predicted by a three-dimensional computational fluid dynamics simulation. The distribution of the typical aerodynamic parameters and the partial flow structures are analysed at design and off-design conditions. Three-dimensional separation near the stall point is effectively suppressed by the aspiration on both hub and shroud, and better performance is achieved by a reasonable increase of aspirated flow rate; a peak efficiency of 0.91 and a total pressure ratio of 1.055 are attained at a total aspirated flow rate of 0.024 kg/s per passage. However, sudden turning of compressor maps at low inlet flow rate occurs without the aspiration on shroud, and a noticeable deterioration in performance occurs with the decreasing of the inlet flow rate. The main reason of performance deterioration is that the flow control efficiency of aspiration is not enough for effectively suppressing three-dimensional separation near the casing corner. The difference in the aspirated flow source is owed to the distinct flow feature at various locations caused by the aspiration efficiency of suction holes. A partial auto-readjustment feature of the suction flow rate with increasing flow separation has been found. The boundary layer suction with an appropriate flow control strategy is necessary for a higher efficiency, highly loaded aspiration compressor.

The effect and injury to the airways of different sputum aspiration pressure in a rat model of mucus hypersecretion

To explore the optimal pressure of sputum aspiration to ensure the effectiveness and safety of clinical operation. We established a rabbit model of airway mucus hypersecretion by aerosol acrolein inhalation, and the animals were divided into 4 groups randomly with different sputum aspiration pressure as follows: group A -75 mmHg (1 mmHg=0.133 kPa), group B -150 mmHg, group C -225 mmHg, group D -300 mmHg. Sputum aspiration efficiency and tracheal mucosal damage degree were evaluated by sputum volume, oxygen saturation changes, the pathological sections of tracheal mucosa and the expressions of IL-1β and TNF-α in airway secretion. The sputum suction volume of group A, B, C, D were (2.72±0.24), (4.81±0.32), (5.03±0.37) and (6.29±0.51) ml, respectively, which was significantly higher in group D, but lower in group A, as compared to other groups (P<0.05). There were no significant differences between B and C groups. The maximal SpO2 decrease of C and D groups [(18.1±5.2)% and(32.4±8.4)%]were significantly higher than those in A and B groups [(4.4±1.7)% and (6.3±2.9)%], and group D was significantly more than group C, and the difference was statistically significant (P<0.05). There were no significant differences between A and B groups. HE staining of tracheal mucosa in C and D groups showed that the inflammatory cell infiltration and mucosal damage were more serious than A and B groups, but the airway mucosal damage of group A was the least. The pressure of -150 mmHg was more effective with high oxygen saturation and less airway injury, which may be suitable for clinical sputum aspiration.

Three-dimensional computational fluid dynamics modeling of particle uptake by an occupational air sampler using manually-scaled and adaptive grids

This work presents fluid flow and particle trajectory simulation studies to determine the aspiration efficiency of a horizontally oriented occupational air sampler using computational fluid dynamics (CFD). Grid adaption and manual scaling of the grids were applied to two sampler prototypes based on a 37-mm cassette. The standard k–ε model was used to simulate the turbulent air flow and a second order streamline-upwind discretization scheme was used to stabilize convective terms of the Navier–Stokes equations. Successively scaled grids for each configuration were created manually and by means of grid adaption using the velocity gradient in the main flow direction. Solutions were verified to assess iterative convergence, grid independence and monotonic convergence. Particle aspiration efficiencies determined for both prototype samplers were undistinguishable, indicating that the porous filter does not play a noticeable role in particle aspiration. Results conclude that grid adaption is a powerful tool that allows to refine specific regions that require lots of detail and therefore better resolve flow detail. It was verified that adaptive grids provided a higher number of locations with monotonic convergence than the manual grids and required the least computational effort.

Sampling efficiency of modified 37-mm sampling cassettes using computational fluid dynamics

ABSTRACTIn the U.S., most industrial hygiene practitioners continue to rely on the closed-face cassette (CFC) to assess worker exposures to hazardous dusts, primarily because ease of use, cost, and familiarity. However, mass concentrations measured with this classic sampler underestimate exposures to larger particles throughout the inhalable particulate mass (IPM) size range (up to aerodynamic diameters of 100 μm). To investigate whether the current 37-mm inlet cap can be redesigned to better meet the IPM sampling criterion, computational fluid dynamics (CFD) models were developed, and particle sampling efficiencies associated with various modifications to the CFC inlet cap were determined. Simulations of fluid flow (standard k-epsilon turbulent model) and particle transport (laminar trajectories, 1–116 μm) were conducted using sampling flow rates of 10 L min−1 in slow moving air (0.2 m s−1) in the facing-the-wind orientation. Combinations of seven inlet shapes and three inlet diameters were evaluated as candidates to replace the current 37-mm inlet cap. For a given inlet geometry, differences in sampler efficiency between inlet diameters averaged less than 1% for particles through 100 μm, but the largest opening was found to increase the efficiency for the 116 μm particles by 14% for the flat inlet cap. A substantial reduction in sampler efficiency was identified for sampler inlets with side walls extending beyond the dimension of the external lip of the current 37-mm CFC. The inlet cap based on the 37-mm CFC dimensions with an expanded 15-mm entry provided the best agreement with facing-the-wind human aspiration efficiency. The sampler efficiency was increased with a flat entry or with a thin central lip adjacent to the new enlarged entry. This work provides a substantial body of sampling efficiency estimates as a function of particle size and inlet geometry for personal aerosol samplers.

An Empirical Model of Human Aspiration in Low-Velocity Air Using CFD Investigations

Computational fluid dynamics (CFD) modeling was performed to investigate the aspiration efficiency of the human head in low velocities to examine whether the current inhaled particulate mass (IPM) sampling criterion matches the aspiration efficiency of an inhaling human in airflows common to worker exposures. Data from both mouth and nose inhalation, averaged to assess omnidirectional aspiration efficiencies, were compiled and used to generate a unifying model to relate particle size to aspiration efficiency of the human head. Multiple linear regression was used to generate an empirical model to estimate human aspiration efficiency and included particle size as well as breathing and freestream velocities as dependent variables. A new set of simulated mouth and nose breathing aspiration efficiencies was generated and used to test the fit of empirical models. Further, empirical relationships between test conditions and CFD estimates of aspiration were compared to experimental data from mannequin studies, including both calm-air and ultra-low velocity experiments. While a linear relationship between particle size and aspiration is reported in calm air studies, the CFD simulations identified a more reasonable fit using the square of particle aerodynamic diameter, which better addressed the shape of the efficiency curve's decline toward zero for large particles. The ultimate goal of this work was to develop an empirical model that incorporates real-world variations in critical factors associated with particle aspiration to inform low-velocity modifications to the inhalable particle sampling criterion.

Enhancing lipoaspirate efficiency by altering liposuction cannula design.

Background:Interplay between the components of a lipoplasty system (suction pump, suction tubing, collection canister, and cannula) determines liposuction efficiency. However, in clinical practice, none of the components are more important than the cannula. Cannula design including port design, port placement, and shaft characteristics is the single most influential contributor to flow resistance and dramatically effects speed of aspiration and final contour. Many variations on port design and placement are available, yet functional enhancements to the cannula shaft have largely been ignored. We have engineered a set of novel cannulas addressing vital elements of cannula design in the effort to enhance aspiration efficiency and efficacy.Methods:Two novel cannula designs (dual- and multiport, in-line configuration), created using a unique proprietary manufacturing process, were evaluated against a popular industry standard design (tri-port, Mercedes configuration) to assess aspiration efficiency. Cannulas with shaft diameters of 3, 4, and 5 mm were attached to a standardized lipoplasty system and evaluated in real time for their ability to aspirate a viscous applesauce medium over a 5-minute time course. For each cannula, we calculated (1) the cross-sectional area of the cannula shaft, (2) single and total port area, (3) port-to-shaft ratio, and (4) theoretical resistance.Results:The relationship between the cannula shaft and cannula port(s) directly influenced flow dynamics. Comparing medium uptake time, aspiration efficiency and the aspiration curves demonstrated a significant improvement of the 2 novel cannulas over the standard cannula in the 5- and 4-mm designations. In the 3-mm group, a difference in uptake time remained. However, a significant difference in aspiration efficiency was only seen between the dual-port novel cannula and tri-port Mercedes standard cannula. Further, differences in the aspiration curves between all 3-mm cannulas approached but did not reach significance.Conclusions:We have developed 2 novel cannulas that maximize port features and seek to minimize the internal shaft resistance. Both designs demonstrate enhanced aspiration and uptake compared with an industry standard design.

Efficacy Assessment of Newly Developed Open-Window Intervention Needles for the Treatment of Cystic Thyroid Nodules That Cannot Be Aspirated

The purpose of this study was to develop a novel open-window needle aspiration method and evaluate its efficacy in drainage and sclerotherapy of cystic thyroid nodules that cannot be aspirated with an 18-gauge needle. Two rectangular windows 5.0 mm in length and 1.0 mm wide were placed at the end of the percutaneous transhepatic cholangiography (PTCA) needle trocar to develop a new open-window intervention needle. The efficiency of the open-window intervention needle was compared either to a porous interventional needle or to an ordinary PTCA needle by assessing the aspiration efficiency. The efficacy of the modified open-window approach was tested by carrying out sclerotherapy and drainage on 21 thyroid cystic nodules that could not be aspirated with an 18-gauge needle and comparing it to aspiration with an 18-gauge PTCA needle of 50 cystic thyroid nodules. The efficacy of aspirating coupling agents of various specifications using the new open-window intervention was superior to aspiration using the PTCA trocar needle or a porous needle (p<0.05). Ethanol ablation efficacy in the treatment of 21 cystic thyroid nodules that could not be aspirated with an 18-gauge needle and the aspiration efficacy of 50 cystic thyroid nodules with an 18-gauge PTCA needle were not significantly different (p>0.05). The new open-window intervention needle approach was highly effective in conducting ethanol ablation of cystic thyroid nodules that could not be aspirated using conventional methodologies.

Hand Calculations for Transport of Radioactive Aerosols through Sampling Systems

Workplace air monitoring programs for sampling radioactive aerosols in nuclear facilities sometimes must rely on sampling systems to move the air to a sample filter in a safe and convenient location. These systems may consist of probes, straight tubing, bends, contractions and other components. Evaluation of these systems for potential loss of radioactive aerosols is important because significant losses can occur. However, it can be very difficult to find fully described equations to model a system manually for a single particle size and even more difficult to evaluate total system efficiency for a polydispersed particle distribution. Some software methods are available, but they may not be directly applicable to the components being evaluated and they may not be completely documented or validated per current software quality assurance requirements. This paper offers a method to model radioactive aerosol transport in sampling systems that is transparent and easily updated with the most applicable models. Calculations are shown with the R Programming Language, but the method is adaptable to other scripting languages. The method has the advantage of transparency and easy verifiability. This paper shows how a set of equations from published aerosol science models may be applied to aspiration and transport efficiency of aerosols in common air sampling system components. An example application using R calculation scripts is demonstrated. The R scripts are provided as electronic attachments.

Influence of secondary aspiration on human aspiration efficiency

Computational fluid dynamics (CFD) was used to evaluate the contribution of secondary aspiration to human aspiration efficiency estimates using a humanoid model with realistic facial features. This study applied coefficient of restitution (CoR) values for working-aged human facial skin to the facial regions on the humanoid CFD model. Aspiration efficiencies for particles ranging from 7 to 116μm were estimated for bounce (allowing for secondary aspiration) and no-bounce (CoR=0) simulations. Fluid simulations used the standard k–epsilon turbulence model over a range of test conditions: three freestream velocities, two breathing modes (mouth and nose breathing, using constant inhalation), three breathing velocities, and five orientations relative to the oncoming wind. Laminar particle trajectory simulations were used to examine inhaled particle transport and estimate aspiration efficiencies. Aspiration efficiency for the realistic CoR simulations, for both mouth- and nose-breathing, decreased with increasing particle size, with aspiration around 50% for 116μm particles. For the CoR=0 simulations, aspiration decreased more rapidly with increasing particle size and approached zero for 116μm compared to realistic CoR models (differences ranged from 0% to 80% over the particle sizes and velocity conditions). Differences in aspiration efficiency were larger with increasing particle size (>52μm) and increased with decreasing freestream velocity and decreasing breathing rate. Secondary aspiration was more important when the humanoid faced the wind, but these contributions to overall aspiration estimates decreased as the humanoid rotated through 90°. There were minimal differences in aspiration between uniform CoR values of 0.5, 0.8, 1.0 and realistic regionally-applied CoR values, indicating differences between mannequin surfaces and between mannequin and human skin will have negligible effect on aspiration for facing-the-wind orientation.

Computational fluid dynamics investigation of human aspiration in low velocity air: orientation effects on nose-breathing simulations.

An understanding of how particles are inhaled into the human nose is important for developing samplers that measure biologically relevant estimates of exposure in the workplace. While previous computational mouth-breathing investigations of particle aspiration have been conducted in slow moving air, nose breathing still required exploration. Computational fluid dynamics was used to estimate nasal aspiration efficiency for an inhaling humanoid form in low velocity wind speeds (0.1-0.4 m s(-1)). Breathing was simplified as continuous inhalation through the nose. Fluid flow and particle trajectories were simulated over seven discrete orientations relative to the oncoming wind (0, 15, 30, 60, 90, 135, 180°). Sensitivities of the model simplification and methods were assessed, particularly the placement of the recessed nostril surface and the size of the nose. Simulations identified higher aspiration (13% on average) when compared to published experimental wind tunnel data. Significant differences in aspiration were identified between nose geometry, with the smaller nose aspirating an average of 8.6% more than the larger nose. Differences in fluid flow solution methods accounted for 2% average differences, on the order of methodological uncertainty. Similar trends to mouth-breathing simulations were observed including increasing aspiration efficiency with decreasing freestream velocity and decreasing aspiration with increasing rotation away from the oncoming wind. These models indicate nasal aspiration in slow moving air occurs only for particles <100 µm.

Variability in coefficient of restitution in human facial skin.

If particles rebound on human facial skin, they can be re-entrained into the airflow and subsequently inhaled, increasing aspiration efficiency estimates. A realistic estimate of facial skin coefficient of restitution (CoR) is necessary to accurately model particle bounce. This study investigated the effects of sampling location, temperature, humidity levels, age, gender, and BMI on facial skin CoR. A torsional ballistometer was used to measure facial CoR for 30 participants divided into three age groups (18-30, 31-40, and 41-65 years), at three temperatures and three humidity levels. The study was repeated twice: once in the late winter and once in the early summer to capture the seasonal variability. The CoR significantly varied across five facial locations, with values ranging from 0.55 to 0.75. Gender, sampling season and the interaction between sampling location and age were found to be significant, but changes in values were relatively small (0.05 at most) and are not considered practically significant. CoR was non-uniform across the face. The use of uniform CoR value as modeling input parameters or for mannequin facial surfaces in experimental wind tunnel studies may not be accurate due to the high variability in CoR between facial sampling locations.

Evaluation of a novel personal nanoparticle sampler

This work investigated the performance in terms of collection efficiency and aspiration efficiency of a personal sampler capable of collecting ultrafine particles (nanoparticles) in the occupational environment. This sampler consists of a cyclone for respirable particle classification, micro-orifice impactor stages with an acceleration nozzle to achieve nanoparticle classification and a backup filter to collect nanoparticles. Collection efficiencies of the cyclone and impactor stages were determined using monodisperse polystyrene latex and silver particles, respectively. Calibration of the cyclone and impactor stages showed 50% cut-off diameters of 3.95 μm and 94.7 nm meeting the design requirements. Aspiration efficiencies of the sampler were tested in a wind tunnel with wind speeds of 0.5, 1.0, and 1.5 m s(-1). The test samplers were mounted on a full size mannequin with three orientations toward the wind direction (0°, 90°, and 180°). Monodisperse oleic acid aerosols tagged with sodium fluorescein in the size range of 2 to 10 μm were used in the test. For particles smaller than 2 μm, the fluorescent polystyrene latex particles were generated by using nebulizers. For comparison of the aspiration efficiency, a NIOSH two-stage personal bioaerosol sampler was also tested. Results showed that the orientation-averaged aspiration efficiency for both samplers was close to the inhalable fraction curve. However, the direction of wind strongly affected the aspiration efficiency. The results also showed that the aspiration efficiency was not affected by the ratio of free-stream velocity to the velocity through the sampler orifice. Our evaluation showed that the current design of the personal sampler met the designed criteria for collecting nanoparticles ≤100 nm in occupational environments.

Anisokinetic Shrouded Nozzle System for Constant Low-Flow Rate Aerosol Sampling from Turbulent Duct Flow

An anisokinetic shrouded nozzle system was designed for sampling particles at a constant low flow rate from a ventilation duct to an aerodynamic particle sizer (APS). Shrouded anisokinetic nozzles are a means for sampling from a moving airstream with higher particle transmission than with unshrouded isokinetic nozzles. This shrouded nozzle sampling system was evaluated in an experimental ventilation duct system. Aspiration and transport efficiency measurements were made for five particle sizes in the range 1–13 μm at each of three duct air speeds in the range 2.2–8.8 m/s. Under these conditions, the shrouded nozzle system showed improved performance compared to buttonhook isokinetic nozzles, especially for larger particles and higher air speeds. Measured transmission efficiencies through the shrouded nozzle sampling system were generally higher and more reliably predictable than those through buttonhook isokinetic nozzles. Model predictions of transport and aspiration efficiencies of the shrouded nozzle s...

Numerical Study of the RespiCon Sampler Performance in the Calm Air

Results of a numerical study of the RespiCon sampler performance in the calm air are presented. The air flow is described by the Navier–Stokes equations of axisymmetric stationary viscous flow of incompressible fluid that are numerically integrated by the computational fluid dynamics (CFD) software FLUENT. The collection efficiencies of RespiCon impactor stages agree quite well with experimental data and curves of the European standards for the thoracic and respirable dust fractions. The aspiration efficiencies derived from the numerical model overestimate the experimental data in the range of particle sizes of 10 μm < dp < 40 μm; however, they correctly predict the value of maximal size of aspirated particles. A new design of the RespiCon sampler with a higher volume flow rate was developed. Copyright 2014 American Association for Aerosol Research

Evaluating Aerosol Aspiration Efficiency in Fast-moving Air

Sampling representative aerosol particles in fast-moving air is a challenging task. Aerosols are significantly more massive than gas molecules, thus they might not follow air streamlines well and could be more easily subjected to sampling errors. This work examines the physical factors that govern the aspiration efficiency of an aerosol sampling probe in unidirectional moving air, and explores the plausible sampling deviations under various high air velocity scenarios. The particle sizes of 0.5 and 5 μm are of particular interest due to their use in defining air cleanliness levels in ISO 14644-1[1] and FED-STD-209.[2]* Our analytical results indicate that significant sampling errors could occur for 5-μm particles when a thick-walled sampling probe is used, or when the air velocity at the sampling probe inlet does not match the velocity of the incoming air (i.e., anisokinetic sampling). The aspiration efficiency of 0.5-μm particles, on the other hand, is nearly 100% due to sufficiently small inertia of these particles.