How does condensation get inside a gas line?

Answer 1

The gas in the line contains a proportion of water vapour (which is also a gas). When the gasses in the line cool below the dew point for the gas water vapour mixture, water condenses out of the gasses inside the gas pipe.

Answer 2

Condensation can form inside a gas line when warm air comes into contact with the cold gas pipe, causing the moisture in the warm air to condense and accumulate inside the line over time. It is important to prevent this condensation as it can lead to corrosion and other issues within the gas line. This can be mitigated by insulating the gas line to prevent temperature differentials that can lead to condensation.