Beijing plans to finish building its PM2.5 monitor network across the city by the end of September, according to the official website of Beijing Municipal Environmental Protection Bureau.

PM2.5 refers to particulate matter with a diameter of 2.5 micrometers or less. These air pollutant particles can invade even the smallest airways.

Thirty-five monitoring stations will be built before collected data is published. The bureau is also working on an emergency plan for heavy pollution days.