| Indoor volatile organic compounds(VOCs)exposure is closely related to human health.The research of indoor pollutant concentration and health risk provides data and scientific support for controlling indoor pollutant concentration and establishing control system.In the previous studies of health risk assessment,most of the exposure parameters are not the characteristic parameters of the specific population.Meanwhile,time distribution of the population is closely related to exposure time.Rational use of time-weighted model and establishment of a reasonable risk assessment model are the basis for calculating the health risk level.In the study of VOCs emission rate,most of the previous studies are carried out in the chamber to study the emission characteristics of some or several VOCs,but this conclusion is difficult to apply in the actual environment.The source of VOCs in the actual environment is difficult to determine,and the indoor environment is in a dynamic change.Establishing the accurate model to calculate VOCs emission rates can provide guidance for indoor air control strategies and provide guidance for the establishment of indoor environment optimization strategies.Most of the residential buildings adopt mixed ventilation mode,almost no regional ventilation and protected ventilation mode are used in the residences.However,people stay in the residences for much longer than any other indoor environments.Controlling the indoor air quality of residential buildings can greatly improve human health.It is necessary to develop a ventilation system which can meet the health needs and thermal comfort of human body in different modes of activity state.Therefore,relevant studies have been carried out,the primary conclusions are as follows:Firstly,the VOCs concentration levels in residences in the main urban area of Chongqing were tested.Benzene,toluene,xylene,butyl acetate and formaldehyde have the high concentration levels.BTX accounted for more than 55% of indoor air environment.The concentration of styrene,cumene and undecane is very low,and the detection rate is not more than 50%.In particular,styrene is only detected in some bedrooms,while undecane is only detected in some living rooms and kitchens.In all three different functional rooms,the proportion of v styrene,isopropylbenzene and undecane were not more than 5%.By comparing with similar studies in developed countries and other regions of China,it is found that the indoor environment level in developed countries is generally better than that in Chongqing,while there is little difference in VOCs concentration between other regions of China.As renovation and decoration materials containing VOCs are widely used in Chinese residences,indoor air quality problems in China need more attention than developed countries.Secondly,based on Monte Carlo simulation method,considering the uncertainty of exposure parameters,the evaluation system of population inhalation exposure was established.The non-carcinogenic risk and carcinogenic risk of adult males and females in Chongqing were evaluated by calculating and selecting different exposure parameters.The results showed that among the eight VOCs studied,toluene had the largest daily intake,followed by formaldehyde and xylene,while styrene,cumene and undecane had the smallest daily intake.Health risk assessment shows that the long-term inhalation exposure of adult males and females in Chongqing is much lower than the long-term inhalation exposure limit(REL),and most of them are at safe level.For carcinogenic risk assessment,the increase of inhalation exposure risk of adult males and females in Chongqing is more than 1.0 ×10-6,long-term exposure to this environment,adult males and females have a higher risk of cancer.By comparing the contribution of exposure,it is found that the concentration is the most important contribution.Among them,the concentration in bedroom has the most important contribution,while the contribution in kitchen is very low.This is closely related to the time distribution of people in different functional rooms determined in the study,and the body weight of people which is the most important factor besides oncentration.Then,by comparing the indoor and outdoor formaldehyde concentration,there is no significant difference between indoor and outdoor formaldehyde concentration in Chongqing urban area.The correlation analysis also points out that indoor formaldehyde pollution is mainly caused by the emission of indoor sources.Based on this,the indoor formaldehyde emission model was established.The human activity schedule and the formaldehyde released by human breathing were taken into account in the model,and the effects of different factors on the emission rate were studied.The results show that the formaldehyde emission rate during daytime is higher than that at nighttime,which may be caused by the difference of ventilation mode,temperature and human activity schedule.According to the results of sensitivity analysis,pollution source control is an effective method to control indoor concentration.Because indoor pollutant concentration mainly comes from indoor pollutant source itself,and the difference between indoor pollutant concentration and formaldehyde concentration in outdoor environment is very small.The purifier can provide better indoor air quality.Thirdly,through experiment in lab,real subject test and software simulation,the thermal plume characteristics of human body in sitting and sleeping posture are studied.It is found that when there are no ventilation modes in the room,the thermal plume around human body is the dominant factor of indoor air flow.Controlling the flow of human thermal plumes is the key to control the air quality in the breathing area.The change and development characteristics of human thermal plumes were studied by experiments on different postures.Based on the study of different breathing modes to modify the thermal plume,it is found that the nose can provide better air quality than mouth breathing in sitting posture,while in sleeping posture,no matter which breathing mode,pollutants will smoothly enter the breathing area with the flow of indoor air.Finally,the laminar air supply device is modified and applied in the simulated bedroom and living room environment.The effect of optimized regional laminar air distribution mode is studied through different air supply velocities.When the supply air velocity is set to the middle level,the pollutant removal efficiencies measured in sitting and sleeping posture experiments are over 80%.For sitting posture,the contaminant exposure index is below 0.3,and for sleeping posture,the contaminant exposure index is below 0.5.Regional laminar air has the characteristics of protected regional ventilation,meeting the health needs of the breathing area,while meeting other parameters,it can also provide better quality air.Regional laminar air supply has a positive effect on improving indoor air quality.It can reduce the concentration of gaseous pollutants in the respiratory region and meet the needs of human health. |
PDF Full Text Request