Search

The time-lag method is the most useful technique to determine gas permeability, diffusivity, and solubility. However, it is difficult to evaluate the transport properties of the membrane accurately because gas permeability depends on the technique used to assess gas flow. The significance of the present study is to design an economic isochoric apparatus to accurately measure micro-range gas flow rates ranging from 10−6 to 10 cm3(STP) s−1. A strategic procedure is demonstrated to eliminate possible artifacts while conducting the gas permeation experiments, including utilizing downstream pressure rise profiles to identify nanoscale defects as well as transient and steady-state permeation. An indigenous apparatus was developed to estimate the polymeric intrinsic properties of the dense and thin-film composite membranes. The device has been successfully used to measure the gas permeation flow rate ranging from 1 × 10−5 to 1 × 10−1cm3 (STP) s−1, which indicates the broad applicability and reproducibility of the data suggesting the reliability of the designed apparatus. Permeation flow rates of binary mixtures of CO2/CH4 through the defect-free membranes were compared with the numerical estimations to validate the measured transport properties. [ABSTRACT FROM AUTHOR]

The people typically spend most of their time at home and schools and also it workplaces for teachers and administrators and service staff, who might spend even more time than children in school buildings. In view of this, indoor radon concentration has been carried out in selected residential and schools located in Mandya, Karnataka, using solid-state nuclear track detector technique. Annual mean values of222Rn in selected schools and houses were found to be 17.4 and 23.3 Bq/m3, respectively. The data distribution was discussed using lognormal probability plots. The doses to different organs and tissues were calculated using the ICRP model of the respiratory tract, and intercomparison of risk is discussed. It can be seen that the larger fraction of the dose is delivered to the lungs (69%) and extrathoracic region (31%) of the body. [ABSTRACT FROM AUTHOR]

The results of radon concentration measurements carried out in dwellings with natural ventilation for 1 y in Bangalore are reported. Measurements, covering three sessions of the day (morning, afternoon, night) were performed two times in a month for 1 y at a fixed place of each dwelling at a height of 1 m above the ground surface in selected dwellings. The low-level radon detection system (LLRDS), an active method, was used for the estimation of radon concentration. The measurements were aimed to understand the diurnal variation and the effect of ventilation rate and flooring type on indoor radon concentration. The geometric mean (± geometric standard deviation) of indoor radon concentration from about 500 measurements carried out in 20 dwellings is found to be 25.4 ± 1.54 Bq m−3. The morning, afternoon and night averages were found to be 42.6 ± 2.05, 15.3 ± 2.18 and 28.5 ± 2.2 Bq m−3, respectively. The approximate natural ventilation rates of the dwellings were calculated using the PHPAIDA—the on-line natural ventilation, mixed mode and air infiltration rate calculation algorithm and their effects on indoor radon concentrations were studied. The inhalation dose and the lung cancer risk due to indoor radon exposure were found to be 0.66 mSv y−1 and 11.9 per 106 persons, respectively. The gamma exposure rate was also measured in all the dwellings and its correlation with the inhalation dose rate was studied. [ABSTRACT FROM PUBLISHER]