Why do we not use oxygen to purge hvac system?

Using oxygen to purge an HVAC system is not advisable because oxygen can support combustion, creating a potential fire hazard, especially in systems that may have flammable debris or materials. Additionally, the presence of oxygen can lead to corrosion and deterioration of metal components over time. Instead, nitrogen is typically used for purging because it is inert, non-combustible, and effectively removes moisture and contaminants without posing safety risks.