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The autoignition of a substance is the temperature at which the vapor of a liquid or gas ignites spontaneously from the heat of the environment without the presence of an ignition source such as a spark or flame. AIT is the temperature at which air oxidation leads to ignition. Autoignition, by its very nature, is dependent on the chemical and physical properties of the material and the method used for its determination. Factors that can influence Autoignition Temperature include ignition delay, vapor concentration, test volume, pressure, oxygen content, and catalytic material. The test is predominantly conducted on gases, however liquids and solids capable of full vaporization should be tested using this method.


Different concentrations of the material are prepared. A selected concentration of the material, typically 100µl is injected into a heated and thermally stabilized, 500 ml round bottom flask with a hypodermic syringe.

Once an ignition temperature is observed, the flask temperature is reduced, and the material concentration is varied until an auto-ignition temperature is established. The temperature of the flask is increased in steps of 30ᣞC when ignition is not observed within 10 minutes and the concentration varied until ignition is observed. The test is continued until the temperature between ignition and non-ignition is 3ᣞC.

Applicable Standard

ASTM E659 ‘’Standard Test Method for Autoignition Temperature of Chemicals’’

Data Interpretation

The auto-ignition temperature is required to define the maximum permitted surface temperature of electrical and non-electrical equipment used in areas where potential testing material is present. This allows for the correct and appropriate designation of equipment based on their temperature or “T” Class. Below are AIT’s of several flammable liquids;

  • Acetic acid : 175 °C
  • Benzene : 298 °C
  • Diethylamine : 312 °C
  • Diethyl Ether : 160 °C
  • Ethyl acetate : 410 °C

When to perform AIT

The autoignition temperature test for substances is typically recommended in several scenarios to assess the risk of spontaneous ignition without an external ignition source. Industries dealing with chemicals often require SDS that include key safety information. Determining the autoignition temperature is essential for accurate SDS preparation. Prior to handling, storing, or transporting materials, knowing the autoignition temperature helps establish safe operating conditions and storage parameters to prevent spontaneous ignition. When selecting materials for specific applications, understanding their autoignition temperature aids in choosing suitable materials that won’t spontaneously ignite under operational conditions. Many safety standards and regulations mandate the determination of autoignition temperatures for substances used in various industries, ensuring compliance with safety guidelines.

Why work with Prime Process Safety Center

  • Prime Process Safety Center is a leader in process safety testing with very experienced laboratory personnel. At Prime Process Safety Center our goal is to provide accurate, reliable and defensible data that meets industry and regulatory standards. We understand the need for the quality of your data, and we work assiduously to achieve just that.
  • We are knowledgeable and experienced in performing autoignition temperature tests, ensuring accurate and reliable results.
  • We have state-of-the-art autoignition temperature testing equipment, providing precise and sensitive measurements.
  • We follow strict testing protocols and quality control measures to ensure consistent and reliable test results.
  • Our team can interpret and analyze the data obtained from the tests, providing valuable insights and recommendations for your specific application or research.


What is Autoignition Temperature?

Answer: Autoignition temperature refers to the lowest temperature at which a substance spontaneously ignites without an external ignition source or flame, simply due to the heat of the material itself.

Why is Autoignition Temperature Important?

Answer: Knowing the autoignition temperature of a substance is crucial for understanding its potential fire hazards, determining safe handling and storage conditions, and ensuring workplace safety.

How is Autoignition Temperature Determined?

Answer: Autoignition temperature is determined through standardized laboratory testing methods. Common techniques include heating the substance in a controlled environment and observing at what temperature it ignites.

What Factors Influence Autoignition Temperature?

Answer: Various factors affect the autoignition temperature, such as the chemical composition of the substance, pressure, presence of impurities, and environmental conditions like humidity.

How is Autoignition Temperature Used in Industry?

Answer: Autoignition temperature data is utilized in industry for risk assessment, safety protocol development, material selection, storage and handling guidelines, and compliance with safety regulations.