Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
비탁계를 사용하여 공기 중의 입자 농도를 측정할 수 있습니다.bitakgye-reul sayonghayeo gonggi jung-ui ipja nongdo-reul cheugjeonghal su itsseumnida.A nephelometer can be used to measure the concentration of particles in the air.