What is autogenous ignition temperature (AIT) and why is it relevant for self-heating cargoes?

• A. The temperature at which a substance ignites with an external spark; relevant to all cargoes.
• B. The ambient temperature on deck; relevant for all operations.
• C. The temperature at which a substance can ignite without an external source; self-heating cargoes can reach this temperature in confinement.
• D. The boiling point of cargo; relevant to stability.

Answer: (D)

Autogenous ignition temperature is the temperature at which a substance can ignite in air without any external ignition source. This matters for self-heating cargoes because heat generated by internal oxidation can build up inside a confined space where heat cannot escape easily. When the temperature of the cargo climbs to the AIT, spontaneous ignition can occur without a spark or flame, which is a major safety risk on ships. Knowing the AIT helps with monitoring pile temperatures, ensuring adequate ventilation, and applying cooling or segregation measures to prevent reaching that point. The boiling point is not about ignition-at all; it tells you when a liquid will vaporize, not when it will ignite in air, and ignition with an external spark describes a different process than autogenous ignition.