What do the simplest power source units use for plasma and cooling gas?

The simplest power source units in plasma arc cutting often utilize filtered, compressed air as both the plasma gas and the cooling gas. This is primarily due to the accessibility, affordability, and effectiveness of air in the cutting process. When compressed air is used as the plasma gas, it can ionize effectively to create the high-temperature plasma needed for cutting through materials.

Air also serves as a cooling medium, which is essential for preventing overheating in the torch and ensuring the longevity of the equipment. Additionally, using filtered air helps to avoid contaminants that could affect the quality and stability of the plasma arc.

Other gases, while they have their own advantages, typically require more specialized equipment or may be more costly. For instance, helium, nitrogen, and pure oxygen can produce different cutting characteristics but are not as commonly used in basic setups where simplicity and cost-efficiency are prioritized.