[News Terms] One Cause of Wildfires: 'Natural Ignition'

'Spontaneous combustion' refers to the phenomenon where a substance naturally generates heat through a chemical reaction in the air, and as this heat accumulates over a long period, it reaches the ignition point and ignites.

When the surrounding temperature is high, the reaction rate of the substance increases, and heat generation rises. In conditions like these days, with almost no rain, dry forests, and high temperatures, the possibility of spontaneous combustion also increases. The firefighting industry generally considers the risk of spontaneous combustion to be high under natural conditions of temperatures above 30℃, humidity below 30%, and wind speeds of 30 km/h.

Dead trees drying out due to pests and diseases become dry, and when the wind causes dry trees to rub against each other, the frictional heat can create sparks. Also, water droplets left inside discarded PET bottles and broken glass pieces left by hikers can act as convex lenses, igniting sparks.

On the afternoon of the 2nd, a firefighting helicopter is conducting extinguishing operations at Inwangsan Mountain in Jongno-gu, Seoul, where a wildfire occurred.
[Photo by Yonhap News]

Recently, wildfires have been occurring consecutively. Fire authorities investigating the causes of the fires believe that the increased number of hikers during the spring outing season likely caused the wildfires by accident, but they are also considering the possibility of spontaneous combustion.

According to wildfire statistics from the Korea Forest Service, over the past 10 years (2012?2021), an average of 481 wildfires occurred annually, destroying 1,087 hectares of forest. Among these, the number of fires in March and April were 123.6 and 105.5 respectively, accounting for 47.6% of the total. The causes of wildfires are 34% due to careless fire by visitors, 15% from burning of rice paddies and fields, 14% from garbage burning, 5% from cigarette fires, and 32% from other causes.

According to the Korea Fire Insurance Association, since spontaneous combustion is also possible in ordinary households, special caution is required when dry and hot weather persists. There have been cases of spontaneous combustion in coal piles stacked at coastal yards, in outdoor warehouses storing sesame meal, in perilla powder left outside refrigerators, in compost yards, and even in latex left on indoor window chairs in ordinary homes.