Just curious I've always wondered, how can you confirm the gas that is supposed to be in your windows, is in the window? I know what a broken seal looks like but, how do you know it's in there from the begining? Can you expose the window to some sort of special light or something to confirm the gas is in there?
When a seal is broken or on the way typically condesation will develop between the panes -- and over time the LOW E will also oxidze and show a definitive haze.
Otherwise you may also take the temperature of the glass on the outside and then on the inside of the glass - Since Gas deals with conductivity of heat pass through you should see a significant temperature between the two panes.
You should also feel the convection from a high emperature variance from the outside to the inside (a draft) through the glass - not around the window.
Any reputable company would also have resource to test.
Good luck with the project.
Radio shack has digital themometers for like 50 bucks.