Which substance could create a dangerous condition when checking a refrigeration system for leaks?

When checking a refrigeration system for leaks, the substance that could create a dangerous condition is Carbon Dioxide. This gas, in high concentrations, can displace oxygen in the air and lead to asphyxiation. Carbon Dioxide is also a heavier-than-air gas, meaning it can accumulate in low-lying areas, further increasing the risk of reduced oxygen levels for anyone present.

In scenarios involving a leak test within a confined space or an environment that doesn't have proper ventilation, using Carbon Dioxide can pose serious health risks. Unlike R-22, Nitrogen, and Oxygen, which have their unique properties and risks, Carbon Dioxide specifically can create an immediate hazard by affecting the breathable air quality. Therefore, when working in or around refrigeration systems, it is vital to exercise caution, especially with substances like Carbon Dioxide.