Indoor Air Environment—Hygienic Factors and Limits

Complaints on the indoor environment of the residents in recent decades have become a common problem in the Swedish housing. The buildings themselves are said to be the cause of problems, and it is given a vague picture of both the exposure and the effect of the problems. The symptoms that residents and users state are often common in the population such as headache, fatigue, mucosal disorders and skin problems. It must be considered that the air that people routinely inhale contains impurities of various kinds, both in- and outdoors. An important source of contamination indoors is the microorganisms that are pathogenic, so called agents. Examples of infectious agents are viruses, fungi, bacteria and protozoa. The purpose of this project is to examine whether a physical measurement is possible to obtain for identifying a possible threshold level of air pollution in the indoor environment. In this study, carried out through physical measurements, the results show major deficiencies in the Swedish school environment. If we study the emissions in the important health-related size range of particles larger than 5.0 microns, before and after measures, the environmental benefits are clarified since over 90% of contaminants larger than 5.0 microns have been eliminated.

A Comparison of Relative Humidity between Two Swedish Buildings with Different Ventilation Solutions

This project is based on measurements of the parameter relative humidity, RH (%), in two buildings: one with natural ventilation and one with mechanical ventilation. Both buildings are located in central Sweden, which constitutes a representative climate zone with respect to Swedish conditions. An important factor for the indoor environment, which affects human health and well-being, is the level of the relative humidity, RH (%). Research studies show that the healthiest level should be in the range of 40% - 60%. Surveys have revealed that about 70% of the employees at Swedish offices, schools and kindergartens experience that the air is too dry during the winter season. Previous studies show that the level of relative humidity in the indoor environment influences the prevalence of respiratory infections and allergies. The purpose of this study is to investigate how the relative humidity differ between the two buildings, and if this may be a cause of the health problems that users are affected by. During many years, users have complained about the environment in the building with mechanical ventilation and that they suffer from health problems. The method used in the study is air measurements of the two parameters, relative humidity and air temperature in the two buildings using data loggers. The indoor environment is affected by the outdoor climate and therefore instruments are placed outdoors to record seasonal variations. The measurements were carried out during the period October 2014 to September 2015 to include all of Sweden’s four seasons with completely different climatic conditions. The results of this study show that the relative humidity in the mechanically ventilated building is consistently significantly lower than in the building with natural ventilation whatever the time of year and temperature indoors. This study shows that mechanical ventilation in buildings affects the indoor environment negatively with respect to human health during most time of the year and this fact must be taken into consideration for the existing as well as the planning of new ventilation systems.

Effect of TiO_2 calcination temperature on the photocatalytic oxidation of gaseous NH_3

Carbon-modified titanium dioxide （TiO2） was prepared by a sol-gel method using tetrabutyl titanate as precursor, with calcination at various temperatures, and tested for the photocatalytic oxidation （PCO） of gaseous NH3 under visible and UV light. The test results showed that no samples had visible light activity, while the TiO2 calcined at 400℃ had the best UV light activity among the series of catalysts, and was even much better than the commercial catalyst P25. The catalysts were then characterized by X-ray diffractometry, Brunauer-Emmett-Teller adsorption analysis, Raman spectroscopy, thermogravimetry/differential scanning calorimetry coupled with mass spectrometry, ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy. It was shown that the carbon species residuals on the catalyst surfaces induced the visible light adsorption of the samples calcined in the low temperature range （〈 300℃）. However, the surface acid sites played a determining role in the PCO of NH3 under visible and UV light over the series of catalysts. Although the samples calcined at low temperatures had very high SSA, good crystallinity, strong visible light absorption and also low PL emission intensity, they showed very low PCO activity due to their very low number of acid sites for NH3 adsorption and activation. The TiO2 sample calcined at 400℃ contained the highest number of acid sites among the series of catalysts, therefore showing the highest performance for the PCO of NH3 under UV light.