The municipal weather centre said humidity and lack of wind would mean the smog will linger for another two days, before a cold front arrives on Wednesday.
The reading for the PM2.5, airborne particles smaller than 2.5 microns in diameter, hit 274 micrograms per cubic meter today in most parts of the capital.
The smog alert in Beijing for the last two days was yellow.
Under the orange weather alert mechanism, industrial plants are required to reduce or shut down production; construction sites to stop the transportation of materials and waste and heavy-duty trucks to remain off the roads.
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China's chronic pollution problem has been linked to hundreds of thousands of premature deaths, and has become a major source of problem for the government to grapple with.
Particulates are the deadliest form of air pollution due to their ability to penetrate deep into the lungs and blood streams, causing permanent DNA mutations, heart attacks, and premature death.
The smaller PM2.5 are particularly deadly, with a 36 per cent increase in lung cancer as it can penetrate deeper into the lungs.