Thailand's tried for years to solve its pollution problem, but 'haze season' always comes back

When the haze season comes, villagers in northern Thailand start preparing the land for fire. They set areas of forest alight, part of controlled burns that will clear their fields for planting — and before long large plumes of smoke rise up, adding to some of the worst air in the world. It's a practice that is unavoidable due to the mountainous terrain, which prevents harvesting machines from operating. During the haze season, from February to April, Chiang Mai city regularly tops the list of the world’s worst cities for air pollution. At nearby Chiang Mai university, an app called FireD has been developed to try to control burning. People register their planned fires through the app. It uses weather and satellite data to predict if a fire on a particular day will cause more pollution or whether conditions will blow away the smoke and pollutants.