What is the Difference Between Flash Point and Auto Ignition Temperature?

The flash point and auto-ignition temperature are two important parameters related to the flammability of substances. Here are the key differences between them:

Flash Point: This is the lowest temperature at which a substance's vapors will ignite with the introduction of an external ignition source, such as a flame or spark. If the temperature of the substance is below its flash point, it will not ignite even in the presence of an ignition source.
Auto-Ignition Temperature: This is the lowest ambient temperature at which a substance will spontaneously combust without the presence of an ignition source. It is the minimum temperature at which a fluid will ignite by itself, without any external ignition.

In summary:

The flash point requires an external ignition source to initiate combustion.
The auto-ignition temperature does not require an external ignition source; the substance ignites spontaneously.

These two parameters are crucial for understanding the flammability and combustibility of substances, as well as for assessing the risks associated with their storage and handling. It is essential to be aware of the flash point and auto-ignition temperature of any flammable substances in your workplace or other environments to ensure safe handling and storage practices.

On this page

What is the Difference Between Flash Point and Auto Ignition Temperature?

Comparative Table: Flash Point vs Auto Ignition Temperature

The flash point and auto ignition temperature are both related to the flammability of a substance, but they represent different concepts. Here is a table summarizing the differences between the two:

Property	Flash Point	Auto Ignition Temperature
Definition	The lowest temperature at which a substance vaporizes into a gas, which can be ignited with the introduction of an external source of fire.	The lowest temperature at which a substance will spontaneously ignite without a source of ignition.
Requirements	Requires an ignition source to initiate combustion.	Does not require an ignition source, as the substance ignites spontaneously.
Measurement Methods	Open cup and closed cup measurements are used to determine flash points.	Auto-ignition temperatures are measured by placing the substance in a vessel and controlling the temperature.
Safety	Flash points are generally considered safer than auto-ignition temperatures, as they are lower. This makes flash points more widely accepted.	Auto-ignition temperatures are generally higher than flash points, which can pose a higher risk in certain workplace environments.

To determine the flash point and auto-ignition temperature of a flammable liquid, it is essential to refer to the Safety Data Sheet (SDS) of the individual chemical product.

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.