| COVID-19 is wreaking havoc around the world,causing enormous damage to countries.More than 100,000 health care workers have been infected with COVID-19 worldwide,and the World Health Organization issued a warning on 21 2020 specifically targeting health care workers.It is generally believed in the scientific community that respiratory droplets are the main vector of SARS-Co V-2 virus transmission,and pathogens carrying droplets or droplets nuclei enter the human respiratory tract or lungs and cause infection.Health care workers are more likely to be exposed to the exhaled airflow of patients during treatment,which increases the risk of cross-infection.Therefore,how to reduce the risk of cross-infection and protect the safety of medical staff through effective ventilation intervention is of great significance.Mixed ventilation is a common form of air distribution in a doctor-patient consultation environment.Whether this air distribution form can effectively reduce the exposure risk of doctors remains to be discussed.Secondly,the relationship between air volume and exposure risk of doctors remains unclear.Therefore,this paper studies the exposure risk of doctors in doctor-patient consultation environments under different air distribution forms and air volume conditions and explores the intervention methods that can effectively reduce the infection risk of doctors in consultation environments.In this paper,a numerical human model was used to truly restore the doctor-patient consultation scene through field research on the hospital consultation scene,to determine the doctor-patient spacing and head-turning data in the common consultation environment,which were used as the basis for the posture adjustment of the numerical human model.Based on the established real doctor-patient consultation scenario,a numerical simulation study was conducted on the exposure risk of doctors under various ventilation forms(mixed ventilation,displacement ventilation,and personalized ventilation).The number of droplets inhaled by doctors and the number of droplets deposited in various parts of doctors was statistically analyzed,and the risk of inhalation exposure,mucosal exposure,and contact exposure of doctors was quantitatively analyzed.The intervention effect of different ventilation forms is evaluated by using this as an evaluation index,and reasonable protection suggestions are put forward.The typical working condition in this paper is set as mixed ventilation and ventilation times of 3h-1.In this working condition,different breathing boundary conditions of the human body are used to simulate the normal breathing and speaking activities of the human body.The breathing curve in the normal breathing state adopts the sinusoidal form,while the breathing curve in the talking state is simplified to the constant flow rate form.The number of droplets inhaled by the physician was used as a core indicator to quantify the physician’s exposure risk for different respiratory activities.The results showed that doctors were at higher risk of exposure when the patients were talking compared to when they were breathing normally,with an approximately 1.1-fold increase in inhaled droplets.The number of droplets deposited in eyes and lips increased by 1.59 times and 2.46 times,respectively.At the same time,the exposure risk analysis of doctors under the condition of exhaling different particle sizes showed that: with the increase of particle size,the number of droplets inhaled by doctors,the number of droplets deposited on the face,lips,and eyes all decreased;However,the amount of deposition on the head and body of doctors increased with the increase of particle size.However,the number of droplets deposited on the doctor’s eyes and lips increased significantly when the patient was speaking,which were 1.59 times and 2.46 times of the amount deposited on the doctor’s eyes and lips during sinusoidal breathing,respectively.At the same time,the effects of different particle sizes on the exposure risk of doctors were compared.When the particle size increased,the number of droplets inhaled,the number of droplets deposited on the face,lips,and eyes decreased.However,the number of droplets deposited on the head and body of doctors increased with the increase of particle size.Based on the doctor-patient consultation scene,the exposure risk of the doctorpatient consultation scene was studied under different ventilation times and different ventilation modes.The effects of different ventilation times on the movement characteristics of exhaled droplets and the exposure risk of doctors were compared under mixed ventilation and displacement ventilation conditions.The results showed that increasing the ventilation rate had no obvious effect on reducing the number of droplets in the respiratory area of doctors,and increased the number of droplets deposited on the body and head of doctors,but significantly reduced the number of droplets inhaled and the number of droplets deposited on the face,lips,and eyes of doctors under mixed ventilation.Under displacement ventilation,increasing ventilation times could significantly reduce the number of droplets in the respiratory area of doctors,but the number of droplets inhaled by doctors and the amount of deposition in the face,lips,and eyes did not decrease.Therefore,in the doctor-patient interview scenario,the increased ventilation frequency of mixed ventilation helps to reduce the risk of inhalation exposure but also increases the exposure risk of exposure.However,displacement ventilation increased the frequency of ventilation but did not significantly reduce the risk of inhalation exposure,mucosal exposure,and contact exposure.Based on the doctor-patient consultation scenario,the exposure risks in the doctor consultation scenario were studied for four different personalized ventilation modes,and the exposure risks of doctors under different personalized ventilation modes were compared and analyzed.The study showed that under the intervention of PV-1 and PV-2air supply modes,the number of droplets inhaled by doctors decreased significantly,but the deposition amount of doctors’ face,head,and the body was still high,which could not effectively reduce the exposure risk.Compared with the typical conditions,the number of droplets deposited on the head of the doctor increased by 2.7 times when PV-1 was used,and the number of droplets deposited on the body part of the doctor increased by 11 times when PV-2 was used.Under the intervention of PE1 and PE-2,the number of droplets inhaled and deposited on the lips,face,head,and body of doctors decreased significantly.Compared with the typical conditions,the number of droplets inhaled by the doctors decreased by 99.4% when PE-1 was used,and by 96.6%when PE-2 was used. |
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