Nuclear weapon effects
Overpressure
The pressure above atmospheric pressure produced by the blast wave of a nuclear detonation, measured in pounds per square inch (PSI).
Nuclear blast damage is conventionally categorized by overpressure. 20 PSI destroys reinforced concrete buildings; 5 PSI collapses most residential structures and is the canonical "city killing" threshold; 1 PSI shatters windows and causes light injuries. Overpressure radius scales with yield to the 1/3 power.
Related terms
PSI (Pounds per Square Inch)
The unit used to measure blast overpressure from a nuclear detonation.
Fireball
The sphere of plasma created by a nuclear detonation, with internal temperatures exceeding 10 million °C — hotter than the surface of the Sun.
Air Burst
A nuclear detonation above the ground at optimal altitude, maximizing the area affected by blast and thermal radiation while producing minimal fallout.
Surface Burst
A nuclear detonation at ground level, producing roughly 40-50% smaller blast radius than an air burst but creating massive radioactive fallout.