# Auto-Ignition Temperature (AIT) #fundamental #chemistry #safety Auto-Ignition Temperature (AIT) is the minimum temperature at which a gas or vapor will spontaneously ignite without an external ignition source, under standard atmospheric conditions. ## Definition - Also known as ignition temperature - Defined in IEC 60079-4 - Process is called heat-ignition (opposite of spark-ignition) - Independent of pressure and temperature for volume concentration ## Key Examples - Methane: 595°C - Carbon Disulfide: < 100°C (lowest known) - Gasoline/Diesel/Kerosene: ~200°C - Ethers and Aldehydes: < 200°C ## Safety Relationship - Equipment temperature class must be lower than the AIT of gases present - T3 equipment (200°C max) cannot be used for gases with AIT < 200°C - This relationship ensures equipment surfaces won't ignite surrounding gases ## Measurement AIT is determined under standard conditions and represents the surface temperature that can cause ignition. ## Related Concepts - [[Temperature Classes]] - [[Hazardous Area Classification]]