 Fires in Kalimantan produce great amounts of smoke, burn a long time and are difficult to extinguish because they are on peatland, and once lit the fires can burn for months and release gases that produce sulphuric acid.Air quality across the region appeared to improve in late October as heavy rainfall doused fires in Indonesia.Brunei, an independent sultanate that is surrounded by East Malaysia's Sarawak state on Borneo, had been affected by the haze from Kalimantan.