BEIJING, Sept. 28 (Xinhua) -- Beijing authorities on Friday started to release official air quality data collected by 20 monitoring stations scattered across the city.

Real-time data regarding particulate matter (PM) 2.5 will be released regularly starting from Friday, an official from the Beijing Environmental Protection Monitoring Center said.

The PM2.5 air quality standard monitors fine particles with a diameter of 2.5 microns or less.

The city's air quality monitoring network is designed to accommodate a total of 35 monitoring stations, with 20 stations in operation as of Friday, the official said.

The rest of the stations will start operating on a trial basis during the upcoming National Day holiday and are expected to produce data by early October, the official said.

PM2.5 readings from most of the operational stations were significantly reduced on Friday due to continuous strong winds that have battered the capital for the last two days.

Data from individual stations does not reflect the entire city's air quality and more monitoring will be done over the next three months, the official said.

The center will release an evaluation of the city's air quality in Jan. 2013 according to the national Ambient Air Quality Standard. Enditem