What is one of the effects of the primary blast?

The primary blast effect refers to the injuries and damage caused directly by the shockwave produced during an explosion. This shockwave travels at high speeds, creating a rapid increase in pressure that can lead to various types of trauma, particularly to air-filled organs such as the lungs, ears, and gastrointestinal tract. This can result in pneumothorax, tympanic membrane rupture, or other forms of internal injury without any external projectiles or heat being involved.

In contrast, the other options listed pertain to secondary effects of an explosion. Injury from debris involves objects being propelled by the blast, burns from heat relate to the thermal effects of an explosion, and falling debris injuries are caused by structures or materials collapsing due to the force of the blast. However, the primary blast effect specifically highlights the immediate trauma caused by the shockwave itself.