As smog-hit Beijing enforced its first-ever red alert for pollution on Tuesday, air in the Chinese capital turned 'hazardous' even as restrictions kept half of private cars in the city of over 22 million people off the roads and schools and construction sites closed.
Beijing's air on Tuesday morning turned from 'very unhealthy' to 'hazardous' as PM 2.5 -- particulate matter with size equal to or less than 2.5 micron and the main gauge to identify pollutant particles in the air -- touched 365 compared to Monday's 256 level.
Under the red alert, which is the highest in the four-tier emergency response system created in 2013, all schools have been ordered to be closed, and outdoor construction halted.
The red alert, the most serious level, issued on Monday will last from 7 am on Tuesday to noon on Thursday. Officials also clamped restrictions on factories and traffic.
The Beijing Air Quality Monitor showed the reading of the PM 2.5 -- the particulate matter in the air -- at the United States Embassy at 365 on Tuesday morning.
According to the US embassy classification, anything beyond 300 is categorised as 'hazardous' warranting people to take preventive measures like avoiding outdoor exposure.
A few students showed up at the Beijing No. 2 Experimental Primary School on Monday as the school sent out text messages giving them the choice of staying at home.
He Jinglong, a physical education teacher of the affiliated school of Beijing Jiaotong University, led students in indoor exercise on Monday.
"We designed a set of exercises, especially for smoggy weather to keep students fit," he was quoted as saying by state-run Xinhua news agency.
The Beijing Education Commission issued a notice on Monday night asking all middle, primary schools and kindergartens to suspend classes during the red alert period.
Car use will be limited during the red alert period as cars are allowed on the roads on alternating days depending on the odd or even numbers of their licence plates.
In addition, 30 per cent of the government cars will be banned from streets on an odd/even basis.
The restriction of car use is expected to push an extra two million passengers onto public transport per day.
Beijing will add 21,000 to 25,000 buses, including 8,182 clean-energy buses, to the roads from Tuesday, officials said.
According to the Beijing Municipal Environmental Monitoring Centre, heavy smog will linger until Thursday. It is expected to disperse on Thursday afternoon as a cold front arrives.
The air quality in Beijing in every winter suffers as the city operates dozens of massive coal fired heaters to keep millions of homes warm, but add to the industrial, vehicular pollution besides burning of agricultural waste in the outskirts.