ST. PAUL, MN (KDAL) - The Minnesota Department of Health is urging residents to check their homes for radon gas.  Radon is a naturally occurring, colorless, odorless gas that is present in many homes and is the second leading cause of lung cancer in the U-S.  Tuesday is "Livestrong day" and the Lance Armstrong Foundation wants to see all Minnesota homes tested for radon.  Testing kits are available from county health departments and many hardware stores and are priced under 20 dollars.  The kits can also be obtained at www.health.state.mn.us/radon