Exhaled Airflow Research Articles

Effect of Vocalization on Human Aerosol Dynamics: Whispering Produces More Aerosols than Speaking

ObjectivesSound pressure and exhaled flow have been identified as important factors associated with higher particle emissions. The aim of this study was to assess how different vocalizations affect the particle generation independently from other factors. DesignExperimental study MethodsThirty-three experienced singers repeated two different sentences in normal loudness and whispering. The first sentence consisted mainly of consonants like /k/ and /t/ as well as open vowels, while the second sentence also included the /s/ sound and contained primarily closed vowels. The particle emission was measured using condensation particle counter (CPC, 3775 TSI Inc.) and aerodynamic particle sizer (APS, 3321 TSI Inc.). The CPC measured particle number concentration for particles larger than 4 nm and mainly reflects the number of particles smaller than 0.5 µm since these particles dominate total number concentration. The APS measured particle size distribution and number concentration in the size range of 0.5 – 10 µm and data were divided into > 1 µm and < 1 µm particle size ranges. Generalized linear mixed effects models were constructed to assess the factors affecting particle generation. ResultsWhispering produced more particles than speaking and sentence 1 produced more particles than sentence 2 while speaking. Sound pressure level had effect on particle production independently from vocalization. The effect of exhaled airflow was not statistically significant. ConclusionsBased on our results the type of vocalization has a significant effect on particle production independently from other factors such as sound pressure level.

Flow-Field Inference for Turbulent Exhale Flow Measurement.

Vision-based pulmonary diagnostics present a unique approach for tracking and measuring natural breathing behaviors through remote imaging. While many existing methods correlate chest and diaphragm movements to respiratory behavior, we look at how the direct visualization of thermal CO2 exhale flow patterns can be tracked to directly measure expiratory flow. In this work, we present a novel method for isolating and extracting turbulent exhale flow signals from thermal image sequences through flow-field prediction and optical flow measurement. The objective of this work is to introduce a respiratory diagnostic tool that can be used to capture and quantify natural breathing, to identify and measure respiratory metrics such as breathing rate, flow, and volume. One of the primary contributions of this work is a method for capturing and measuring natural exhale behaviors that describe individualized pulmonary traits. By monitoring subtle individualized respiratory traits, we can perform secondary analysis to identify unique personalized signatures and abnormalities to gain insight into pulmonary function. In our study, we perform data acquisition within a clinical setting to train an inference model (FieldNet) that predicts flow-fields to quantify observed exhale behaviors over time. Expiratory flow measurements capturing individualized flow signatures from our initial cohort demonstrate how the proposed flow field model can be used to isolate and analyze turbulent exhale behaviors and measure anomalous behavior. Our results illustrate that detailed spatial flow analysis can contribute to unique signatures for identifying patient specific natural breathing behaviors and abnormality detection. This provides the first-step towards a non-contact respiratory technology that directly captures effort-independent behaviors based on the direct measurement of imaged CO2 exhaled airflow patterns.

The penetration phenomenon of the expiratory airflow from thermal plume of human body in the microenvironment around people

Understanding the influence of the human body's thermal plume on exhaled airflow is crucial for accurately assessing indoor infection risks. This study employs numerical simulations and a jet integral modeling method to investigate the airflow dispersion patterns of a single thermal manikin during sustained expiration. It was found that the thermal plume formed a two-stage evolution in exhaled airflow. Initially, the airflow was weakened by the thermal plume in the horizontal dispersion, and subsequently it was bent due to the entrainment of the surrounding air in the upward dispersion of the exhaled airflow. The thermal plume changes the trajectory and lateral dispersion distance of exhaled airflow. When the exhalation velocity is 1 m/s, the airflow is fully deflected towards the head plume region. When the exhalation velocity is between 1.5 and 2 m/s, the airflow is partially deflected, with only part of the upper airflow deflected towards the head plume region. In addition, it is interesting to note that the plume changes the dispersion trajectory of the exhaled airflow, while still adhering to the distributions of buoyant jet flow. This study suggests that the thermal effect of the human body is a significant factor in characterizing the dispersion of exhalation airflow and aerosols. Considering the thermal plume in indoor infection risk assessment is expected to yield more reliable data for theoretical modeling of respiratory airflow transport.

Evaluation of the spatial distribution of aerosols produced by various respiratory activities

This study investigated the dispersion and evaporation characteristics of droplets and droplet nuclei emitted during human respiratory activities. A specially designed wind tunnel was filled with purified air, wherein selected subjects performed various respiratory activities with their heads positioned inside. An optical particle sizer was used to collect particles with sizes of 0.3–10 μm at 63 points in front of the mouth. The dilution factors were analyzed to investigate the impact of combining the exhaled airflow with ambient air on droplet evaporation. At a distance of 0.01 m from the mouth opening, the volume concentration of the particles was the highest during breathing, followed by coughing and speaking. The volumetric concentration of particles decreased with an increase in the distance from the inlet for all activities. The spatial volume concentration distribution of particles showed that coughing tended to disperse the particles in the forward direction, whereas speaking tended to disperse them laterally. Utilizing these findings in CFD analysis can provide in-depth insights into dispersion and evaporation dynamics. This can contribute significantly to the development of preventive measures through the implementation of proactive HVAC systems to effectively remove infectious particles and control the spread of infectious diseases. Future studies should explore a wider range of particle sizes and advanced sampling techniques for a clear understanding of respiratory particle dynamics and infection control strategies.

Respiratory particle emission rates from children during speaking

The number of respiratory particles emitted during different respiratory activities is one of the main parameters affecting the airborne transmission of respiratory pathogens. Information on respiratory particle emission rates is mostly available for adults (few studies have investigated adolescents and children) and generally involves a limited number of subjects. In the present paper we attempted to reduce this knowledge gap by conducting an extensive experimental campaign to measure the emission of respiratory particles of more than 400 children aged 6 to 12 years while they pronounced a phonetically balanced word list at two different voice intensity levels (“speaking” and “loudly speaking”). Respiratory particle concentrations, particle distributions, and exhaled air flow rates were measured to estimate the respiratory particle emission rate. Sound pressure levels were also simultaneously measured. We found out that median respiratory particle emission rates for speaking and loudly speaking were 26 particles s−1 (range 7.1–93 particles s−1) and 41 particles s−1 (range 10–146 particles s−1), respectively. Children sex was significant for emission rates, with higher emission rates for males during both speaking and loudly speaking. No effect of age on the emission rates was identified. Concerning particle size distributions, for both respiratory activities, a main mode at approximately 0.6 µm and a second minor mode at < 2 µm were observed, and no differences were found between males and females. This information provides important input parameters in predictive models adopted to estimate the transmission risk of airborne pathogens in indoor spaces.

Low-Order Mechanistic Models for Volumetric and Temporal Capnography: Development, Validation, and Application.

The airflow model's single "alveolar" compartment has compliance and inertance, and feeds a resistive unperfused airway comprising a laminar-flow region followed by a turbulent-mixing region. The gas-mixing model tracks mixing-region CO 2 concentration, which is fitted breath-by-breath to the measured capnogram, yielding estimates of model parameters that characterize the capnogram. For the 17 examined records (310 breaths) of airflow, airway pressure and Tcap from ventilated adult patients, the models fit closely (mean rmse 1% of end-tidal cŞoncentration on Vcap; 1.7% on Tcap). The associated parameters (4 for Vcap, 5 for Tcap) for each exhalation, and airflow parameters for the corresponding forced inhalation, are robustly estimated, and consonant with each other and literature values. The models also allow, using Tcap alone, estimation of the entire exhaled airflow waveform to within a scaling. This suggests new Tcap-based tests, analogous to spirometry but with normal breathing, for discriminating chronic obstructive pulmonary disease (COPD) from congestive heart failure (CHF). A version trained on 15 exhalations from each of 24 COPD/24 CHF Tcap records from one hospital, then tested 100 times with 15 random exhalations from each of 27 COPD/31 CHF Tcap records at another, gave mean accuracy 80.6% (stdev 2.1%). Another version, tested on 29 COPD/32 CHF, yielded AUROC 0.84. Our mechanistic models closely fit Tcap and Vcap measurements, and yield subject-specific parameter estimates. This can inform cardiorespiratory care.

Thermal imaging and velocity measurements of the exhaled airflow in total laryngectomized patients during COVID-19 pandemic.

In patients after total laryngectomies, the trachea and the lung can be easily infected by SARS-CoV-2 because the respiration happens through the tracheostoma. The aim of our study was to examine whether patients with LaryTube™ can distribute aerosols to a greater extent than without LaryTube™, and to observe whether the surface of different protective instruments can be examined using the thermal camera in total laryngectomees. An important objective was also to confirm the assumption that the use of HME (heat and moisture exchanger) alone does not provide protection during COVID-19 pandemic. Finally, during our tests, we tried to get an answer to our assumption that the sample taken from the inner surface of the HME can be tested for SARS-CoV-2. A total of 23 patients who underwent total laryngectomies were analyzed by velocity measurements and thermal imaging with and without HMEs and laryngeal tubes, using different types of PPEs. COVID-19 PCR testing was performed on patient tracheas and the inner surfaces of the HMEs. Male patients with laryngeal tubes without HMEs demonstrated an increase in exhaled airflow velocity of more than 43% compared to male patients without laryngeal tubes; in female patients, the same value was more than 39%. Thermal imaging results confirmed that the lowest surface temperature was measured on FFP2 masks. The sent samples can be tested for SARS-CoV-2 using PCR, the presence of the virus was not detected. Laryngectomized patients without laryngeal tubes pose a lower risk for spreading viral aerosols due to the reduced velocity of the exhaled airflow caused by the absence of the tube as the narrowing factor. Patients with laryngeal tubes who undergo total laryngectomies during the COVID-19 pandemic should use HMEs with viral filter, if possible, also changing the laryngeal tubes to dermal adhesives for fitting their HMEs seems to be the best option. The surface of the used protective equipment can also be examined with thermal camera in the case of total laryngectomees. COVID-19 PCR testing of the tracheal secretion from the inner HME surfaces should become a routine in clinical practice if deemed necessary. Orv Hetil. 2023; 164(34): 1327-1336.

Portable spirometer using pressure-volume method with Bluetooth integration to Android smartphone

&lt;span lang="EN-US"&gt;This paper presents a study on an embedded spirometer using the low-cost MPX5100DP pressure sensor and an Arduino Uno board to measure the air exhaled flow rate and calculate force vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and the FEV1/FVC ratio of human lungs volume. The exhaled air flow rate was measured from differential pressure in the sections of a mouthpiece tube using the venturi effect equation. This constructed mouthpiece and the embedded spirometer resulted in a 96.27% FVC reading accuracy with a deviation of 0.09 L and 98.05% FEV1 accuracy with a deviation of 0.05 L compared to spirometry. This spirometer integrates an HC-05 Bluetooth module for spirometry data transceiving to a smartphone for display and recording in an Android application for further chronic obstructive pulmonary disease (COPD) diagnosis.&lt;/span&gt;

Interactions of exhaled buoyant jet flow and human motion-induced airflow: An experiment study in a water tank

Indoor environments with displacement ventilation or under-floor air distribution commonly exhibit thermal stratification, which can impact the dispersion of droplets in exhaled air by moving human sources. This paper presented an experimental study using a water tank to simulate the coupling characteristics of exhaled airflow and human motion-induced oncoming airflow, especially in a stratified environment. The effects of exhalation velocity and movement speed were studied. Results show that the buoyant jet flow couples with the oncoming flow, firstly spreading forwards and upwards, forming the impinging region, where the penetration distance is found to vary linearly with the ratio of movement velocity and exhalation velocity. Then the coupled flow spreads backwards, forming the wake region behind the source, where the flow rises upwards, albeit at a slower rate than in motionless conditions. In the wake region, there is an obvious stagnant layer, which is exacerbated by the thermal stratification of the ambient fluid and much lower than the lock-up height of motionless buoyant jet flow. It is expected to provide scientific basis for formulating prevention and control measures in public spaces.

Face masks provide high outward protection despite peripheral leakage: Insights from a reduced-order model of face mask aerodynamics

A reduced-order model of face mask aerodynamics and aerosol filtration is introduced. This model incorporates existing empirical data on filtration efficiency for different types of face masks, as well as the size distribution of exhaled aerosol particles. By considering realistic peripheral gap profiles, our model estimates both the extent of peripheral leakage and the fitted filtration efficiency of face masks in terms of outward protection. Simulations employing realistic peripheral gap profiles reveal that, for surgical masks, 80% or more of the total exhaled airflow could leak through the mask periphery, even when the average peripheral gap measures only 0.65 mm. However, the majority of exhaled aerosol particles do not follow the flow path through the peripheral gaps but, instead, impact directly on the mask fabric. As a result, these face masks can filter out approximately 70% of the exhaled particles despite the significant peripheral leakage. To validate our model, we compare its predictions with experimental data, and we find a reasonable agreement in estimating the outward protection provided by surgical masks. This validation underscores the reliability of our model in assessing the efficacy of surgical masks. Moreover, leveraging the insights gained from our model, we explore the impact of mask usage on the transmission of respiratory viruses within communities. By considering various scenarios, we can assess the potential reduction in viral spread achieved through widespread mask adoption.

Numerical investigation of impinging jet ventilation in ICUs: Is thermal stratification a problem?

Intensive care units (ICUs) are the high incidence sites of hospital-acquired infections, where impinging jet ventilation (IJV) shows great potential. Thermal stratification of IJV and its effect on contaminants distribution were systematically investigated in this study. By changing the setting of heat source or the air change rates, the main driving force of supply airflow can be transformed between thermal buoyancy and inertial force, which can be quantitatively described by the dimensionless buoyant jet length scale (). For the investigated air change rates, namely 2 ACH to 12 ACH, varies between 0.20 and 2.80. The thermal buoyancy plays a dominant role in the movement of the horizontally exhaled airflow by the infector under low air change rate, where the temperature gradient is up to 2.45 °C/m. The flow center remains close to the breathing zone of the susceptible ahead, resulting into the highest exposure risk (6.6‰ for 10-µm particles). With higher heat flux of four PC monitors (from 0 W to 125.85 W for each monitor), the temperature gradient in ICU rises from 0.22 °C/m to 1.02 °C/m; however, the average normalized concentration of gaseous contaminants in the occupied zone is reduced from 0.81 to 0.37, because their thermal plumes are also able to carry containments around them to the ceiling-level readily. As the air change rate was increased to 8 ACH (), high momentum weakened the thermal stratification by reducing the temperature gradient to 0.37 °C/m and exhaled flow readily rose above the breathing zone; the intake fraction of susceptible patient located in front of the infector for 10-µm particles reduces to 0.8‰. This study proved the potential application of IJV in ICUs and provides theoretical guidance for its appropriate design.}.

Quantitatively Visualizing Airborne Disease Transmission Risks of Different Exhalation Activities through CO2 Imaging.

Aerosol transmission has played a leading role in COVID-19 pandemic. However, there is still a poor understanding about how it is transmitted. This work was designed to study the exhaled breath flow dynamics and transmission risks under different exhaling modes. Using an infrared photography device, exhaled flow characteristics of different breathing activities, such as deep breathing, dry coughing, and laughing, together with the roles of mouth and nose were characterized by imaging CO2 flow morphologies. Both mouth and nose played an important role in the disease transmission though in the downward direction for the nose. In contrast to the trajectory commonly modeled, the exhaled airflows appeared with turbulent entrainments and obvious irregular movements, particularly the exhalations involving mouth were directed horizontal and had a higher propagation capacity and transmission risk. While the cumulative risk was high for deep breathing, those transient ones from dry coughing, yawning, and laughing were also shown to be significant. Various protective measures including masks, canteen table shields, and wearable devices were visually demonstrated to be effective for altering the exhaled flow directions. This work is useful to understanding the risk of aerosol infection and guiding the formulation of its prevention and control strategies. Experimental data also provide important information for refining model boundary conditions.

Relationship between surgical field contamination by patient's exhaled air and the state of the drapes during eye surgery

The coronavirus disease (COVID-19) pandemic has led to a dramatic increase in facemask use. Consequently, it has been reported that exhaled airflow toward the eyes can cause the dispersal of bacteria into the eyes, potentially increasing the incidence of postoperative endophthalmitis. In addition to wearing a facemask, gaps between the surgical drape and skin can also direct exhaled airflow toward the eyes. Here, we aimed to examine how the risk of contamination varies depending on the state of the drapes. We used a carbon dioxide imaging camera to visualize changes in exhaled airflow under different drape conditions and a particle counter to evaluate changes in the number of particles around the eye. The results revealed airflow present around the eye and a significant increase in the number of particles when the nasal side of the drape was detached from the skin. However, when a metal rod called “rihika” was used to create space above the body, the airflow and number of particles were significantly reduced. Thus, if drape coverage becomes incomplete during surgery, exhaled airflow toward the eye may contaminate the surgical field. On hanging up the drape, airflow can escape in the direction of the body, potentially preventing contamination.

Contactless Breathing Airflow Detection on Smartphone

Accurate and continuous breathing rate detection is crucial as it can help people to assess their physical health and provide early warning and diagnosis for potential human diseases. Traditional breathing detection approaches involving intrusive devices are uncomfortable for long-term continuous monitoring. While contactless detection approaches utilizing radio-frequency (RF) signals or acoustic signals mainly focus on sensing the changes of chest and abdomen displacements, which are not a good indicator recording breathing event due to existing false body movements. In this article, we present Wi-Tracker, a contactless breathing detection system based on commercial off-the-shelf (COTS) smartphones, which detects breathing event through capturing the Doppler effect caused by human exhaled airflow on the reflected acoustic wave. Specifically, Wi-Tracker uses the speaker on smartphone to transmit ultrasound signals and its microphone to receive the reflected acoustic signals recording breathing event. Then, we adopt a cumulative power spectral density (CPSD) method to extract fine-grained breathing pattern from the received signals. Finally, we design algorithms to accurately capture the breathing event from the extracted breathing pattern. We evaluate Wi-Tracker with six volunteers for a period of one month. Experimental results show that Wi-Tracker is able to achieve contactless breathing detection with a mean estimation error (MEE) of 0.17 bpm, which is even better as compared to RFID-based or WiFi-based approaches.

Boundary conditions for exhaled airflow from a cough with a surgical or N95 mask.

Wearing surgical or N95 masks is effective in reducing the infection risks of airborne infectious diseases. However, in the literature there are no detailed boundary conditions for airflow from a cough when a surgical or N95 mask is worn. These boundary conditions are essential for accurate prediction of exhaled particle dispersion by computational fluid dynamics (CFD). This study first constructed a coughing manikin with an exhalation system to simulate a cough from a person. The smoke visualization method was used to measure the airflow profile from a cough. To validate the setup of the coughing manikin, the results were compared with measured data from subject tests reported in the literature. The validated coughing manikin was then used to measure the airflow boundary conditions for a cough when a surgical mask was worn and when an N95 mask was worn, respectively. Finally, this study applied the developed airflow boundary conditions to calculate person‐to‐person particle transport from a cough when masks are worn. The calculated exhaled particle patterns agreed well with the smoke pattern in the visualization experiments. Furthermore, the calculated results indicated that, when the index person wore a surgical and a N95 mask, the total exposure of the receptor was reduced by 93.0% and 98.8%, respectively.

호흡주기 동안 방독면 내 호흡저항 및 내부 온도 변화에 대한 수치해석 연구

We perform numerical simulations of unsteady thermal flows inside a gas mask. Time-dependent respiratory profiles for normal and heavy breathing conditions are imposed at two different inlets, depending on the exhalation and inhalation periods. We assess the respiration resistance (pressure drops) and the regional averaged temperature, considering the effects of nosecup in the gas mask. Simulation results show that the nosecup significantly reduces the exhaled hot airflows to the eye area, reducing the temperature to approximately 26.5°C. In contrast, the maximum of the averaged temperature inside the nosecup is increased by less than 3.6°C during the exhalation period. Under normal and heavy breathing conditions, the nosecup-induced pressure drops during inhalation are approximately 4 Pa and 20 Pa, respectively. However, the induced pressure drops are relatively small than expected from an air purification filter. Thus, the results imply that the nosecup can improve visibility by reducing condensation near the goggles while it can slightly worsen breathing and thermal comfort.

Speech air flow with and without face masks

Face masks slow exhaled air flow and sequester exhaled particles. There are many types of face masks on the market today, each having widely varying fits, filtering, and air redirection characteristics. While particle filtration and flow resistance from masks has been well studied, their effects on speech air flow has not. We built a schlieren system and recorded speech air flow with 14 different face masks, comparing it to mask-less speech. All of the face masks reduced air flow from speech, but some allowed air flow features to reach further than 40 cm from a speaker’s lips and nose within a few seconds, and all the face masks allowed some air to escape above the nose. Evidence from available literature shows that distancing and ventilation in higher-risk indoor environment provide more benefit than wearing a face mask. Our own research shows all the masks we tested provide some additional benefit of restricting air flow from a speaker. However, well-fitted mask specifically designed for the purpose of preventing the spread of disease reduce air flow the most. Future research will study the effects of face masks on speech communication in order to facilitate cost/benefit analysis of mask usage in various environments.

Advanced ventilation chair for source control of respiratory infectious diseases

Since the outbreak of the new crown, a large number of people at home and abroad have been infected, causing great damage to human lives, the economy, and the whole society, which has led to a great deal of concern about respiratory infections. Hospitals are at high risk for the spread of respiratory infections, and hospital outpatient rooms are a focal point for the prevention and control of nosocomial infections due to the small space and frequent visit of many people, where effective measures can greatly reduce the risk of the spread of respiratory infections. Airborne transmission is generally controlled by strengthening ventilation and dilution. However, full space dilution ventilation is less effective in removing exhaled droplet nuclei and is limited by the capacity of the ventilation system and other conditions. Therefore, airborne transmission is a weak section in hospital infection prevention and control, and there is an urgent need to develop advanced technical means aiming for source control. In this paper, computational fluid dynamics (CFD) simulation was used to study the interaction between exhaled airflow, thermal plume, and ventilation airflow when patients stayed in the outpatient consulting room for a short period (from a few minutes to more than ten minutes). After comparing the two styles of wearing mask, it was determined that only the top exhaust was the best distribution form. When patient wear face masks, the top exhaust with ventilation volume rate of 20 m3/h can achieve 90% collection efficiency in 30 s. After the patient left, it takes only 15 s to collect most exhaled particles. The air volume and vent dimension is important to the design of ventilation plate, when the design is not reasonable, it can cause up to 50% impact. This paper propose a personalized ventilated chair for airborne transmission which could contribute new solutions and technologies to achieve the goal of significantly reducing hospital infection rates.

Современное представление о витамине D и генетической регуляции воспаления на примере бронхиальной астмы

Bronchial asthma (BA) is a heterogeneous chronic inflammatory disease characterized by a variety of symptoms in the form of wheezing, breathlessness, chest tightness and/or cough, as well as variable exhaled airflow limitation, with both the combination of symptoms and airflow limitation changing with time and intensity. Asthma is associated with both airway hyperresponsiveness to direct or indirect stimuli and chronic airway inflammation. Therapy for BA in accordance with national guidelines and clinical recommendations successfully controls asthma symptoms in most patients. However, there are several problems. Firstly, up to 5% of patients with asthma have a refractory course, respond inadequately to traditional therapeutic approaches and, therefore, are at greater risk of life-threatening asthma exacerbations. Secondly, a significant number of patients, even with mild to moderate asthma, have poor symptom control and may experience severe exacerbations. Low vitamin D levels are associated with decreased lung function, increased asthma exacerbations, and drug use, although it is not clear whether there is a causal relationship between these observations, and whether asthma patients may benefit from vitamin D supplementation. The authors present in this literature review the mechanisms by which vitamin D can reduce the severity of inflammation in BA. The research is focused on studying the mechanisms of chronic respiratory inflammation and their exogenous and genetic regulation involving genetic variants of the VDR gene and vitamin D metabolites. Keywords: children, vitamin D, 25(OH)D deficiency, asthma, inflammation, VDR

Exhaled Jet and Viral-Laden Aerosol Transport from Nasal Sneezing

The recognition that the spread of COVID-19 is primarily through airborne transmission has brought renewed urgency to understand the spread of aerosols generated from patients. Viral-laden aerosols generated from oral coughs have been well studied; however, aerosols generated from nasal sneezing has been overlooked. This scenario arises from patients who suffer allergenic rhinosinusitis, or the nasal cavity is irritated, particularly during naso-endoscopy. Nasal sneezing is characterised by an explosive blast of air exiting the nostrils, which can be considered as dual jets, resulting in the spread of viral-laden aerosols remaining suspended in the air. This study used computational fluid dynamics consisting of a hybrid RANS-LES turbulence method to model the airflow and the discrete phase model to track aerosol dispersion during nasal sneezing. The results demonstrated that the exhaled airflow jets during nasal sneezing resemble the flow characteristics of two parallel jets in co-flow. These two jets interfere with each other in the merging zone, and after they merge, the sneeze plume expands radially. The nasal sneeze forms a V-shaped plume with smaller particles in the core region. At the end of the sneeze, when the exhaled jets have lost their initial momentum, the large particle dispersion is dominated by gravity. We detected the presence of a ‘sneeze puff’ that transport droplets away from the body, similar to the buoyant puff observed in recent COVID-19 studies of oral coughs.