syttymispiste

Syttymispiste, typically translated as ignition point or autoignition temperature in English, is the minimum temperature at which a material will spontaneously ignite in air without an external ignition source. It is a property of a substance under specified conditions and is usually expressed in degrees Celsius (or Kelvin).

The autoignition temperature depends on multiple factors, including the material’s composition and physical state, particle size or surface area, pressure, oxygen concentration, and heating rate. Test methods involve heating a sample in a controlled furnace or hot-air stream and monitoring whether ignition occurs, following standardized procedures defined by international or national standards. The measured value can vary with test conditions, so it is reported together with the method and atmosphere used.

Understanding syttymispiste is important in process safety, chemical storage, and handling, as substances with low autoignition temperatures can ignite spontaneously at elevated temperatures or during processing if heat buildup occurs. It is distinct from the flash point, which is the lowest temperature at which vapors above a liquid can ignite in the presence of an ignition source. Many safety classifications use autoignition temperature together with other properties to assess fire risk.

Note that syttymispiste is the term used in Finnish technical contexts for autoignition temperature, and it should be interpreted as the temperature at which a material may ignite without an external flame or spark, rather than as a threshold for ignition by external heating alone.