The blast pressure effect includes a positive phase that sends out a shock wave and a negative phase that creates a vacuum.

• A. It is primarily associated with heat generation.
• B. Includes a positive phase that sends out a shock wave and a negative phase that creates a vacuum.
• C. It describes injuries caused by flying debris.
• D. It represents collateral impacts from the blast.

Answer: (B)

The blast pressure effect is defined by a rapid spike in pressure (positive phase) as the blast wave compresses air and forms a shock front, followed by a drop below ambient pressure (negative phase) creating a vacuum or rarefaction. The positive phase delivers the initial impulse and overpressure, while the negative phase produces suction as the air expands back, which can pull objects toward the center. This description precisely matches the idea of a shock wave with both a high-pressure surge and a subsequent vacuum. Heat generation, debris injuries, and collateral impacts are separate aspects and don’t capture this pressure-wave behavior.