When the factory seal fails, water will permeate the area between the two panes and reduce visibility. If the window has not mineral etched (fogged), it is repairable. The seal needs to be repaired or the water will return. No special gasses are used in the assembly of RV dual pane windows.
Adhesive foam spacers, infused with a desiccant, are available on the internet in various thickness to match your needs. I use 3M Windo-weld urethane (pt.# 08609) to reform the seal. A good handy knife, razor blades and lots of cleaning are required.
Richard