The South Korean government is replacing drones with larger and more tech-savvy unmanned airships for more efficient surveillance of fine dust emissions from industrial sites. 

The Environment Ministry said on Thursday that it recently purchased two unmanned aerial vehicles equipped with emission gauges and surveillance cameras and flew them over the national industrial complex in Asan, South Chungcheong Province, for three days. 

Each vehicle is eleven-meters wide and four-point-five-meter tall but only weighs 30 kilograms. 

They can also fly for up to four hours on a single charge and travel up to 140 kilometers per mission. Drones used in such situations are limited by their shorter flying hours.