Flash point and ignition point


Many of the organic solvents we handle have a flash point.


What is a flash point?

The flash point is the lowest temperature at which combustion begins when the ignition source (Source of fire such as fire and static electricity) is brought close to the liquid level.

Conversely, if the liquid has not reached the flash point, it will not ignite even if the ignition source is brought closer to the liquid.

Please refer to the video below.

*There are some exceptions

For example, if there is a “core” on the liquid surface that expands the surface area, such as an “oil stove,” or if it is atomized with a sprayer, it will ignite even below the flash point.


The following are common cases.

  • A rag soaked with liquid ← The rag is the core
  • Liquid with dust on the surface ← Dust becomes the core
  • Apply liquid by spraying ← It is in the form of mist

In these cases, please note that it will ignite even below the flash point.


What is the ignition point?

If the temperature of the flammable liquid continues to rise, it will reach the temperature at which combustion will start without an ignition source.

Normally, flammable liquids do not start burning until they cross the peak of activation energy, as shown in the figure below. However, as the temperature rises, the peak of activation energy becomes lower, and when the peak disappears, it naturally begins to burn.



Light oil indicates high flammability by “cetane number”, and gasoline indicates low flammability by “octane number”.

Why does light oil represent high flammability, while gasoline represents low flammability?

This is because it is said that light oil has better quality when it is easy to ignite spontaneously, and gasoline is said to have better quality when it is hard to ignite spontaneously.

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