Ignition is the point at which heat, spark, or another energy source starts a combustion reaction. In practical terms, it is the moment a material stops merely being warmed or stressed and begins to burn or react chemically. In security work, ignition matters because it defines a critical threshold: once reached, the process can become fast, self-sustaining, and hard or impossible to reverse.
In real systems, ignition can be accidental or deliberate. A high-voltage pulse, overheated component, damaged filament, or misused trigger circuit can supply enough energy to start combustion in pyrotechnic devices, batteries, fuel vapors, or other flammable materials. Defenders and engineers reduce this risk by controlling current, limiting heat buildup, isolating ignition sources, and testing for thermal failure. Understanding ignition helps explain why small hardware changes can have large physical consequences.