Indonesian firefighters in Sumatra and Kalimantan have their work cut out for them in battling fires on peatland across the two regions, which have been the source of the haze in recent weeks.
Trying to contain such fires is not unlike playing "whack-a-mole". The fires smoulder under dry peatland and can surface anywhere to trigger another blaze.
Over half of the raging fires in Pekanbaru in Indonesia's Riau province and elsewhere, causing the haze in Singapore and other towns in West Malaysia, are on peatland.
Peatlands, which are usually waterlogged and formed over thousands of years, consist mainly of decomposed vegetation, making it carbon-rich and highly flammable during the dry season.
When burned, peatlands produce copious amounts of smoke, thus releasing a high level of carbon dioxide into the atmosphere.
The yearly haze problem is the result of slash-and-burn agricultural practices carried out largely by farmers, because it is the fastest and cheapest way of clearing plantations for pulp, oil palm and other crops.
Ironically, planting crops on peatland is not easy or cheap owing to moisture, a lack of nutrients and its high acid content. Peatland is thus not fertile. It is also prone to pests and harmful bacteria that live in the moist sponge-like soil.