The ignition temperature of wood chips is around 250°C. When a pile of wood chips undergoes biological processes, a chemical reaction takes over, causing chemical oxidation. This process produces more heat, moisture, and carbon dioxide, which can cause the temperature in the pile to rise. If the temperature continues to climb, it can eventually hit the ignition temperature of wood, which can cause the chips to ignite. So, it's important to be cautious when handling and storing wood chips to avoid any potential accidents due to self-ignition.