Study On Ventilation Of Chinese Homes And The Associations With Asthma,Allergy And Sick Building Syndrome Symptoms

Ventilation is an important method for reducing indoor pollution.Measuring ventilation is an important part of ascertaining indoor air quality and evaluating occupants’ health in residential buildings.This thesis developed a mass balance method using occupant generated CO₂,investigated the present ventilation situation in Chinese residential buildings,studied associations between ventilation and occupants’ health,and hypothesized the mechanisms by which ventilation impacts health in terms of indoor pollutants.A CO₂ method based on the mass balance of occupant generated CO₂ and using the least squares method has been developed.In the practical applications,this method takes the dwelling’s internal air flow into consideration and can measure air change rates in the bedroom and whole home.The air change rate measured by the CO₂ method is reliable for low air change rates,with an error of-36.52%-+7.75%.A nationwide investigation was carried out during 2017-2018 in order to have a complete view of residential ventilation status in China.Infiltration rate,airing rate and air change rate at night were measured in all 5 climate zones during 4 seasons.By using a tracer gas method,it was found that the median infiltration rate for 294 residences to be 0.34 h-1.By using occupant generated CO₂ as the tracer gas,air change rates over the course of one year in 46 natural ventilated homes and 42 mechanical ventilated homes at night were calculated using mass balance considerations.In 54% of the measurements,windows were closed,so ventilation was only by infiltration.Windows were mainly closed when the outdoor temperature was below 15 °C,and above 26 °C.The median infiltration rates did not differ appreciably among seasons and climate zones,and were always less than 0.45 h-1.In residences with mechanical ventilation,median air change rates were 0.58-1.62 h-1.In order to study the association between ventilation and children’s asthma and allergy,a case-control study was performed.Air change rates were measured in 410 children’s homes in Tianjin and Cangzhou.Questionnaires were used to survey children’s health history.The associations of home ventilation with children’s asthma and allergy were analyzed in different strata of time and space.A low bedroom ventilation at night was significantly associated with an increased proportion of rhinitis among children（rhinitis current,adjusted odds ratio（AOR）: 1.59;95% confidence interval（CI）: 1.01-2.49; diagnosed rhinitis,AOR: 3.02（1.16-7.89））.The findings suggest a dose-response relationship between air change rate at night in children’s bedrooms and rhinitis.The night-time air change rate in bedrooms has a greater impact on health than the whole home air change rate during daytime.The concentrations of phthalates were higher in homes with lower air change rates.A high air change rate can reduce the concentration of HDM（house dust mite）allergens.Inadequate ventilation resulted in elevated concentrations of HDM allergens,and an increased prevalence rate of children’s rhinitis.High HDM allergen concentration and phthalate concentration as the intermediate species could explain how a low air change rate is associated with children’s rhinitis symptoms.In order to study the association between ventilation and sick building syndrome,an investigation of ventilation was carried out in Tianjin.Volatile organic compounds（VOCs）,formaldehyde,PM2.5,ultrafine particle and ozone were measured.Inadequate ventilation resulted in elevated concentrations of formaldehyde and VOCs,and an increased prevalence rate of SBS symptoms among occupants.In conclusion,ventilation in Chinese residential building should be increased.A low bedroom air change rate at night was related to adults’ mucosal SBS symptoms and children’s rhinitis.Exposure to high ultrafine particle concentrations,phthalate concentrations,and house dust mite allergens likely increases the odds of adults’ SBS symptoms and children’s allergic diseases.Improving ventilation could effectively decrease the odds of most studied diseases.