What type of gas reading should be observed to ensure safe purging procedures are followed?

To ensure safe purging procedures are followed, monitoring combustible gas readings is crucial. This measurement is essential because it helps detect any flammable gases present in the environment. During the purging process, it is vital to confirm that any potential hazardous gases are effectively removed from the piping system to prevent explosions or fire hazards. By maintaining combustible gas readings below a certain threshold, safety can be ensured, and the atmosphere can be considered safe for workers involved in the operation.

Temperature and pressure readings are important in other contexts of gas system operation, but they do not directly assess the presence of flammable gases. Air quality index readings typically pertain to general air quality and pollution levels, rather than the specific concern for combustible gas hazards in purging operations. Thus, focusing on combustible gas readings is the most relevant and necessary practice for ensuring safety during purging procedures.