Until 10 years ago, the air in my country was fresh and I could see the blue sky in spring and fall. However, due to the rapidly industrialization of neighboring countries, the air quality has deteriorated and the number of days to wear masks has increased. On a very bad day the air is running an air purifier with the windows of the house closed. I always wonder about indoor air quality, company air quality, and air quality in the subway when commuting. I hope this app has an answer to solve my question.