BEIJING -- Beijing experienced 22 "blue sky" days, or days with fairly good air quality, last month. That was the best run of clear days since the year 2000.

Beijing Environment Protection Administration authorities said that persistent cold air was the major factor that kept the air clear, since updrafts and northerly winds helped disperse pollutants.

Another factor was the closure of more heavily-polluting industrial facilities in or near the capital, with 10 major polluting facilities having been closed. Desulfurization projects are under way at several other facilities.

Beijing had 20 "blue sky" days in January 2007 and 245 such days for the whole year.

This year, the Olympic host city aims to have 70 percent of the days up to standard, which means there should be at least 256 "blue sky" days.

The capital city launched its "blue sky" drive in 1998.