Thanks!
I see that Walmart is listing them now @ $32, shipped by third parties but for free. With a +10ppm variance, you can't take them seriously other than "if any CO found, reject tank."
I pulled my car out of the garage the other morning for a remote start warm-up since I always back into my garage to avoid running over any kids when I leave. The rear of my car was several feet from the garage, the garage door open, and there was no wind, but the Sensorcon CO I wear was giving a consistent 40ppm warning as I walked around inside the garage.