We had a radon reading in our first house we moved into back in 2007, it read enough that we had an abatement system put in. My TV and gaming rig were in the basement, never had any issues. Split entry similar to your setup. The house we are currently in we moved into in 2011, Radon reading didn't register enough to need abatement. Basement is unfinished so the only time I spend down in basement is grabbing beer and running on the treadmill. Our garage opens from the basement to the back yard and I brew there with the door open. When I finally get around to getting the basement finished to make my proper mancave/bar I will probably test again. If you're concerned you can get someone to come check for you. Tests typically take 2-7 days. An abatement system isn't too costly and gives peace of mind.