To combat persisting high levels of pollution and smog, Beijing Municipal Education Commission announced that starting today air purification systems would be installed in some of the city's schools and kindergartens.<br/><br/>State-run Xinhua news agency reported that, the city government has allocated money to help the schools cover the cost of the installation. The announcement came last night in the wake of Beijing extending its orange alert for heavy air pollution again as smog is expected to persist until the weekend. On Tuesday, the national observatory issued a red alert for fog and renewed an orange alert for smog in a number of northern, eastern and central regions.<br/><br/>Many regions in China have experienced heavy smog since Friday last week. Schools and other education institutions in the city have been ordered to stop outdoor courses and activities. China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.