Study On The Mechanism Of Aerosol Diffusion And The Effect Of Ventilation Control In Dental Office

In the era of "appearance economy",oral health and dental aesthetics have attracted more and more attention from young consumers.Therefore,due to the nature of work,the dental office has become a key place for the spread of the epidemic.During oral surgery,the use of surgical equipment may further promote the vaporization and atomization of saliva,blood,and tissue fluid in the patient’s mouth to form droplets and aerosols.In the dental office,the installation position of the return air outlet of the air-conditioning system is limited by the space,resulting in unreasonable airflow distribution in the room,and the traditional ventilation method may not meet the hygienic standards.Therefore,it is very important to study the diffusion mechanism and removal effect of airflow and aerosol in the dental office.In this study,a dental office laboratory platform was built,and airflow experiments and aerosol concentration test experiments were carried out.Based on the experiments,a numerical model is established.In order to obtain the mechanism of aerosol diffusion in the dental clinic and the effect of different ventilation modes,this study conducted a numerical simulation study on the influence of different influencing factors on the indoor airflow and aerosol distribution.At the same time,a comparative study of the new attachment ventilation(AV)mode and the traditional mixed ventilation(MV)mode was carried out.In addition,local purification measures are proposed,and a more reasonable airflow organization is used to optimize the indoor airflow to improve the air quality of the office.The main conclusions are as follows:In this study,the diffusion mechanism and distribution of aerosols in the dental office under the conditions of human thermal plume and ventilation mode were obtained.At a lower background wind speed,the thermal plume effect of the human body is more obvious,and the aerosol will flow to the upper space with the action of the thermal plume of the human body.A good aerosol removal effect cannot be achieved only by relying on the thermal plume effect.From the perspective of removal rate,MV is slightly better than AV;from the perspective of aerosol destination distribution,AV is better than MV,and the exhaust outlet is located in the upper part than in the lower part.Airflow organization form is one of the main factors affecting aerosol removal.Under the isothermal working conditions of AV and MV,for the research on the influencing factors and effects of aerosol in the dental office,the ventilation effect has not been significantly improved after continuing to increase the number of air exchange rate.Therefore,the air exchange rate is not the most important factor in determining the behavior of aerosol particles after reaching a certain height.From the perspective of aerosol destination distribution,AV was superior to MV in terms of deposition rate and escape rate,but was slightly inferior to MV in terms of suspension rate.On this basis,airflow optimization measures and ventilation strategies under the AV were proposed in this study.After adding deflectors and changing the position of the exhaust outlet to the lower part,it was found that there is no advantage in the removal rate of indoor aerosols.After turning on the portable air cleaner(PAC),a very obvious ventilation effect has been achieved,and all evaluation indicators are better than other working conditions.Among them,compared with no PAC,the aerosol deposition rate in this mode is reduced by 15.33%,the escape rate has decreased by 2.66%,and the escape rate has increased by 17.99%,which reduces the risk of infection of personnel.In addition,due to the effect of gravity,aerosols will first be deposited on the surface of the patient’s body,so more than 5% of the aerosols were detected on the surface of the patient.Therefore,wearing protective clothing for the patient during the operation is recommended.For non-isothermal conditions,due to the heavy cold air during cooling in summer,more aerosols carried by the airflow will be deposited on the ground,which also leads to a lower escape rate in summer conditions.On the contrary,the aerosol escape rate is higher under heating conditions in winter.Overall,the effect of winter conditions is slightly better than that of summer conditions.However,the effect of non-isothermal conditions is similar to that of isothermal conditions,which also verifies that the aerosol removal effect has a weak relationship with temperature.This study puts forward the application of different ventilation modes in the dental office,and concludes that the optimal ventilation strategy in this study is the joint operation mode of AV and PAC.In addition,the recommendations made in this study can guide the health protection and epidemic prevention of personnel in dental offices.