BEIJING - Beijing has recorded three fewer "blue sky days" in the past 11 months of the year compared to the same period last year.

The city reported 22 days with grade I or II air quality in November, an increase of 4 days compared with the same period last year, according to the Beijing Municipal Environmental Protection Bureau.

However, Beijing also experienced several days of poor air quality as a result of bad weather conditions. Factors such as weaker winds and a rise in humidity are unsuitable for the dispersal of atmospheric pollutants, the environmental watchdog said.

The environmental bureau has been keeping a close watch on construction sites and coal-fired boilers in order to reduce emissions of pollutants since the city began supplying heat in mid-November.

Beijing uses a five-grade classification of air quality on the basis of pollution indices, with grade I being the best and grade V the worst. Days with grade I or II air quality are considered "blue sky days."

The municipal government has vowed to hit 274 "blue sky days" this year, and it still needs 13 "blue sky days" in order to achieve this goal by the end of the year.

Meanwhile, air quality monitoring in Beijing made headlines recently due to public debate over different standards of measurements.

China currently uses PM10, or particular matter under 10 micrometers, to measure air quality, but the public has urged government authorities to apply the tighter PM2.5 standard, which measures finer matter that is considered more hazardous to people's health as it can go deeper into the lungs.

The Ministry of Environmental Protection said it has been considering revising present standards, and a new index standard which includes the measuring of PM2.5 and ozone density is scheduled to be fully implemented nationwide in 2016 with pilot projects conducted in certain regions ahead of the national deadline.