Thanks guys.
I think it might have been allergies as well. I felt like I had an upset stomach, but the feelings went away. It also didn't feel as bad as when I was outside.
I hardly get the feeling at my own home; must be because of a greater air exchange.

Good to know it isn't radon.
BTW, what sort of radioactivity does radon produce? Alpha? Beta? Both?

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I calculated the odds of this succeeding versus the odds I was doing something incredibly stupid...and I went ahead anyway. - Crow T. Robot

Godspeed, John Glenn. - Scott Carpenter

And these atomic bombs that science burst upon the world that night were strange even to the men that used them.
- H.G Wells, The World Set Free

To the conspiracy crowd, radiation is a big Boogey Man that inspires terror and death in all who encounter it. - JayUtah