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The methods of experimental measurements and theoretical calculation are used to research the relationship of indoor CO2 concentration and building air tightness in natural ventilation and mechanical ventilation, respectively. Three experimental conditions of windows closed and opened are designed. The blower door test method is used to test natural ventilation, and the indoor CO2 concentration is tested. The general ventilation theoretical calculation formula is used to calculate the indoor CO2 concentration of mechanical ventilation conditions. The results show that the indoor CO2 concentration difference of windows opened and closed is about 20% in natural ventilation, and it is 10% in mechanical ventilation. [ABSTRACT FROM AUTHOR]

China is one of the countries with serious forest fires. Besides the methods of strengthening management of fire source and increasing forest fire monitoring and rescue efforts, improving the ability of forest itself to resist fire is also the key to prevent forest fires. In this study, we examined the characteristics of the bark across 11 main tree species in Korean pine broad-leaved forest at Jiaohe Forestry Experimental Area in Jilin Province. Fire resistance of bark acorss the tree species was evaluated comprehensively with four indices of water content, ash content, calorific value and oxygen index, using the methods of entropy weight, variance analysis and cluster analysis. Results showed that water content of bark was the highest in Phellodendron amurense. Calorific value of bark was the lowest and ash content was the highest in Ulmus davidiana. Oxygen index of bark was the highest in Fraxinus mandshurica. Bark fire resistance of 11 tree species followed the order of U. davidiana > Acer mono > Acer triflorum > Acer mandshuricum > F. mandshurica > Quercus mongolica > P. amurense > Tilia amurensis > Juglans mandshurica > Pinus koraiensis > Betula costata. The tree species in Korean pine broad-leaved forest could be classified to five categories according to bark fire resistance: U. davidiana belonged to the category of strongest fire-resistance; A. mono and A. triflorum belonged to the category of strong fire-resistance; A. mandshuricum, F. mandshurica, Q. mongolica, P. amurense, T. amurensis belonged to the category of common fire-resistance; J. mandshurica and P. koraiensis belonged to the category of weak fire-resistance; and B. costata belonged to the category of poor fire-resistance.