In order to meet the national standard and public needs for Seoul Metro subway, air purification has been taken into a consistent consideration with the addition of high quality control facilities. This work focuses on the review of the cost effectiveness to improve the air filtration of an MVAC (mechanical ventilation & air conditioning) in a field subway. The inflow PM₁₀ and PM_2.5 into the test MVAC chamber were 19.4 kg/yr and 8.9 kg/yr respectively. It corresponds to the environmental cost of 5,857,000 won for PM₁₀ and 6,608,000 won for PM_2.5 every year. While the current filtration system collects approximately 55% of the inlet PM₁₀ and 35% of PM_2.5, a new lay-out showed 80% for PM₁₀ and 55% for PM_2.5. The new design presented the environmental benefit for PM10 with 1,464,000 won, whilst the additional cost required 3,192,744 won. In the future, however, the increase of environmental benefits for the indoor dust over the atmospheric aerosols will more or less compensate the potential cost.

Seoul is one of the most dynamic capital cities in the world of which population is about 10.49 million. The air quality of Seoul subway is a great concern to users and the public authorities, especially the pollution of particulate matters. The metallic particulate matters are generated from the friction of wheels and subway rails, which causes dispersion into the platform and even to the trains. This study attempted to characterize the current filters in subway MVAC system and a newly developed filter which was a type of thin electret fiber bundle. Collection efficiency of the filtration system varies from 20% to 90% depending on filter life and dust particle size. The removal of fine dust with diameter smaller than 1㎛, which could not be well achieved by current filtration system, is very important in the subway air cleaning system. The new electret filter was found to have a high potential for the use in subway MVAC with high collection efficiency, especially for fine mode dust.