Place the operating end of an argon analyzer against an argon-filled window's glass. If the window has a low-emissivity (low-e) glass coating, then test the side of the window that isn't coated.
Turn on the argon analyzer. The analyzer will measure the amount of argon in the window.
Interpret the result that appears on the argon analyzer's display screen. The result probably is a percentage. The ideal percentage of argon in windows for maximum energy efficiency is 90 percent or greater. A window has no or very little argon if the analyzer displays an error message or a very low percentage.