During the blast pressure effect, what is the initial phase called?

During the blast pressure effect, what is the initial phase called?

• A. Negative Phase
• B. Early Phase
• C. Primary Phase
• D. Positive Phase

Answer: (D)

In a blast pressure effect, the initial portion is the positive phase. This is the sharp spike in pressure caused by the detonation’s shock front, where air is rapidly compressed and pressure rises well above ambient. That overpressure is what drives most of the early damage to structures and objects. After this surge, the pressure swings below ambient in the negative phase as the gases expand and rarefy. Terms like early phase or primary phase aren’t standard descriptors for this first, high-overpressure moment, making the positive phase the precise label for the initial event.

In a blast pressure effect, the initial portion is the positive phase. This is the sharp spike in pressure caused by the detonation’s shock front, where air is rapidly compressed and pressure rises well above ambient. That overpressure is what drives most of the early damage to structures and objects. After this surge, the pressure swings below ambient in the negative phase as the gases expand and rarefy. Terms like early phase or primary phase aren’t standard descriptors for this first, high-overpressure moment, making the positive phase the precise label for the initial event.