What must be done after an oxygen system has been opened to the atmosphere?

Selecting the necessity of purging an oxygen system of moisture after it has been opened to the atmosphere is based on the understanding of how moisture can affect the performance and safety of the system. The introduction of moisture can lead to corrosion and can also create hazardous conditions if the oxygen system is used in conjunction with flammable materials. Purging the system ensures that any moisture is removed, maintaining the integrity and functionality of the oxygen setup.

In this context, the focus is on the importance of ensuring that the oxygen system remains free of contaminants. While inspecting for leaks is a routine safety procedure, it does not specifically address the critical concern of moisture contamination. Refilling the system immediately may not be advisable until the moisture issue is resolved, as introducing more oxygen without addressing the contamination could pose safety risks. Lastly, using the system without further action is not advisable because it could compromise the safety and efficiency of the oxygen delivery during flight situations. Thus, appropriately purging the system of moisture is a necessary step after exposure to the atmosphere.