On Windows, which it sounds like you're using, find this
file: c:\program files\common files\Adobe AIR\Versions\1.0\Adobe
AIR.dll. Right-click and select properties; the version tab will
show you the version number.
This may get outdated, but as of AIR 1.5.3 the paths are:
Mac OS X
Open the/Library/Frameworks/Adobe AIR.framework/Versions/1.0/Resources/Info.plisttext file and locatethe<key>CFBundleVersion</key>entry. The corresponding string entry represents the version of AIR, for example:<string>220.127.116.1130</string>
Open theApolloVersiontext filelocatedinside the/opt/Adobe AIR/Versions/1.0/Resourcesdirectory (for example theApolloVersiontext file would show18.104.22.16830)