The fate of inhaled aerosol particles within the respiratory tract is determined by factors such as the particle size distribution, breathing pattern, and airway geometry. Thus, matching the aerosol therapy device to the patient is crucial to achieving a high target site dose and minimizing side effects. High output efficiency and minimal residual volume have been reported for vibrating mesh nebulizers, which generate a high percentage of particles in the respirable fraction. Using custom-made plates, this work aimed to investigate and identify the major operating parameters of these devices and their effects on the characteristics of the aerosol output.Each plate contained between 279 and 4606 tapered apertures that ranged from 3 to 12 µm in diameter and were uniformly sized per plate. To investigate the effect of coagulation during droplet generation, the distance between the apertures was varied from 75 to 450 µm. The resonance frequency of the piezoelectric element was scanned, and the aperture plates were then vibrated at a fixed frequency (100-300 kHz), causing the ejection of liquid droplets. The nebulizers were mainly evaluated using a 0.9% sodium chloride solution. A syringe pump injected the solution into the vibrating mesh plates. The aerosol output was carried, dried, and introduced into the mixing chamber by a dilution air flow of 160 L min -1 . An aerosol size spectrometer was employed to measure both the number concentration and the size distribution of the output.The droplet size increased with the aperture diameter. The distance between apertures did not affect the number concentration or the size distribution of the generated droplets. The droplet size decreased as the resonance frequency increased, but the extent was less than we expected. Each mesh possessed an optimal vibration frequency, which varied according to the size and the number of the apertures, for consistently maximizing the aerosol output. The optimal feeding rate increased with the number of apertures and the applied electric current, but the aerosol size distribution remained the same. Additionally, our results using a cotton wick to deliver the solution from the reservoir to the vibrating mesh indicate that fibrous sorbent materials can potentially replace the syringe pump.
This study characterized the effects of smoldering incenses and combustion conditions on gaseous pollutant yields. Incense comes in three types: non-smoke (A), reduced-smoke (B) and traditional-smoke incense (C and D). Each incense type was burned in a test chamber with various combustion conditions (airflow rate and relative humidity). An extractive Fourier transform infrared (FTIR) was used to measure gas pollutants from smoldering incense in real time. Concentrations of methane, ethylene, methanol, formaldehyde and ammonia were measured using the IR spectra of smoldering incense samples. The resulting order of total emission factors of the identified gas pollutants (sum of methane, ethylene, methanol, formaldehyde and ammonia) were non-smoke < reduced-smoke < traditional smoke incenses. Total gas-pollutant emission rates and factors increased logarithmically as the airflow rate increased (2-28 L/min). Finally, the emission rates and factors of ethylene and methane decreased linearly as relative humidity increased (18-97%), while those for ammonia, methanol and formaldehyde increased. Results can be utilized to solve indoor air pollution problems caused by burning incense. Assuming that incense will continue to be burned when paying respect to ancestors, using incense made of lowvolatility materials, with high carbon levels, low airflow rates and high environmental relative humidity can minimize gas-pollutant production.
The generation of aerosols during "silent" tidal breathing via the bronchiole fluid film burst (BFFB) mechanism, which involves the rupturing of mucus meniscus or film in terminal bronchioles, has been described in recent studies. To replicate the BFFB mechanism and identify the characteristics of aerosol generation during normal breathing, this study set up a single-film generation system employing tubes ranging from 0.7 to 2.94 cm in diameter that simulated the bronchioles. A liquid film of artificial mucus or soap solution was applied on the bottom of each tube and moved upward by filtered carrier air, which eventually led to the rupturing of the film. The resultant airborne particles (> 7 nm) were then counted with a condensation particle counter, and the number size distributions (0.6-20 µm) were measured with an Aerodynamic Particle Sizer. The experimental results show that the film's rising velocity, rise distance and surface tension in addition to the tube diameter all affected the total particle count and the size distribution. The total particle count increased with the rising velocity until the latter reached 3 cm s -1 and then decreased as the velocity continued growing-a phenomenon that was mainly due to the curvature of the film increasing with the velocity. Moreover, the larger the tube diameter, the higher the particle count. When a 0.9% NaCl solution was added to increase the surface tension of the film, the total particle count decreased as the surface tension increased, regardless of whether artificial mucus or soap solution was used. This approach to reducing the propagation of infectious diseases in healthcare facilities seems to merit further exploration.
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