New Delhi, May 31 -- Non-residential high-rise buildings more than five storeys tall will need to install and use anti-smog guns, the government has ordered in a plan aimed at reducing urban air pollution. The order, issued by the environment department on May 29, applies to commercial complexes, malls, and hotels with a built-up area greater than 3,000 square metres, and to office and institutional buildings that are at least ground plus five floors tall. Residential houses, apartment complexes, and group housing societies have been exempt. According to the directive, the applicable buildings will have to install anti-smog guns within the next six months and operate them throughout the year, except the monsoon - between June 15 and October...