EB789320 wrote:
no readings were in the high 20's in the area. Also, my mistake the airport was Schaumburg airport, not DuPage.
This is concerning because my regular waist high background readings are between 15-27 CPM using the same type of geiger counter as you.
Have your readings returned to the middle 20's?
Side note: I find the graph display setting on the GMC-3xx to be useless, I prefer for myself using the large CPM display function with the backlight locked on.