Final answer:
Carbon dioxide (CO2) is the agent most commonly used to induce pneumoperitoneum for laparoscopic procedures due to its safety profile and physiologic compatibility.
Step-by-step explanation:
The agent typically used for inducing pneumoperitoneum during a diagnostic laparoscopy is carbon dioxide (CO2). This gas is preferred because it is non-flammable, which is a critical safety feature considering the use of electrical equipment during surgery. Additionally, carbon dioxide is readily absorbed by tissue and removed by the respiratory system, which makes it safer in instances of inadvertent intravascular placement or gas embolism. Helium, argon, air, and nitrogen are not commonly used for this purpose due to various risks such as air embolism, difficulty in absorption, and flammability potential.