가스생산기지의 탱크보수와 가스배관 기밀시험 및 가스치완에 사용되는 질소는 액화질소를 기화시켜 공급하고 있으며, 불활성 가스인 질소의 용도는 천연가스 설비에서 선박용까지 그 사용처가 다양하다. 질소발생기술은 극저온증류식(Cryogenic distillation), 흡착식(Pressure Swing Adsorption), 분리막식(Membrane)이 있으며 극저온증류식은 장치비가 높아 대형플랜트에 적합하고 흡착식 및 분리막식은 중소규모에 적합하다. 특히, 분리막식은 장치가 간단하고 진동에 대한 성능저하가 없어 이동식 질소발생에 적합한 기술이다. 분리막 방식의 이동식 질소발생플랜트의 설계기술은 분리막모듈, 장비, 배관, 전기, 진동, 에너지 관리 등의 최적화를 통해 이루어진다.

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and NO2 generation rate were estimated. Mean of ventilation rate was 1.41 ACH in houses, assuming a residential NO2 deposition constant of 0.94 hr-1. Mean generation rate of NO2 was 16.5 ppbv/hr. According to house characterization, inside smoking and family number were higher NO2 generation rates, and apartment was higher than single-family house. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

Indoor air quality is affected by source strength of pollutants, ventilation rate, decay rate, outdoor level, and so on. Although technologies measuring these factors exist directly, direct measurements of all factors are not always practical in most field studies. The purpose of this study was to develop an alternative method to estimate these factors by application of multiple measurements. For the total duration of 30 days, daily indoor and outdoor NO2 concentrations were measured in 30 houses in Brisbane, Australia, and for 21 days in 40 houses in Seoul, Korea, respectively. Using a box model by mass balance and linear regression analysis, penetration factor (ventilation divided by sum of air exchange rate and deposition constant) and source strength factor (emission rate divided by sum of air exchange rate and deposition constant) were calculated. Subsequently, the ventilation and source strength were estimated. In Brisbane, the penetration factors were 0.59±0.14 and they were unaffected by the presence of a gas range. During sampling period, geometric mean of natural ventilation was estimated to be 1.10±1.51 ACH, assuming a residential NO2 decay rate of 0.8 hr-1 in Brisbane. In Seoul, natural ventilation was 1.15±1.73 ACH with residential NO2 decay rate of 0.94 hr-1. Source strength of NO2 in the houses with gas range (12.7±9.8 ppb/hr) were significantly higher than those in houses with an electric range (2.8±2.6 ppb/hr) in Brisbane. In Seoul, source strength in the houses with gas range were 16.8±8.2 ppb/hr. Conclusively, indoor air quality using box model by mass balance was effectively characterized.