overp"essure wil-]. be given in all three units. 2. Compared to the blast of a large chernica] expl-osion, the d.uration of that fron a nuclear exp.Losion is considerably longer except for very sma.1l yield weapons - of the order of l- second for a 20 kt. burst and severa]. second.s for a 1Mt. burst. Since the dsmage caused. by blast increases with the duration as well as the magnitudeof the static and. dynamic overpressures, a nuclear explosion is more devastating than a chemica]. blast at a d.istance where both would have the same Deak overDressure. 3. A.Il nuclear air bursts - regardless of the design of the weapon - will release a la-r:ge portion of their tota"1 energy as blast. For a ristand.ardt' veapon this wilL anount to approximately 50 per cent. Hence, this is a naJor cause of damage. l+. Intuitively one night believe that the strongest blB.st would be p"oduced. at a given distance from grormd. zero when the nuclear weapon is detonated as a surface explosion. Due to reflections of the air shock wave against the ground, however,this is not true. For a given weapon yiel-d and a given level- of blast overpressure, there is ahtays a particu.l-ar height of burst that maxirizes the area covered by atleast that overpressure. This height of burst varies vith the leve]. of overpressure chosen. Ilence if the aim is to opti$ize d.estruction of a solidly built industrial seeti.on, tbe height of burst shou-ld be somewhat lower than if maxinum d.estruction of a resiclential area is intenaled. 5. With increasing height of burst bhe overpressure that reaches the ground. decreases rapitlly. As the height of the burst is lowered under the optimization height for some ovexpressure, the area covered by that overpressu?e decreases somer^rhat. fn the inned.iate vicinity of g"ound zero, hoveve?, blast wi]-]. become
**Analysis**
The text appears to be discussing the effects of nuclear explosions on the environment and human populations. It provides technical details about the blast waves, overpressures, and destruction caused by such explosions, suggesting a focus on the scientific and technological aspects of nuclear warfare.

**Category**
Science and technology