BRAWM Question: testing food with Geiger counter
We have all seen blogs and demos of people testing various items such as food, rainwater, seaweed, etc with Geiger counters.
Question: If someone claims to have taken background samples of 38 CPM and tested food at 55 CPM, is that food safe?
I'm not an expert, but neither are most bloggers, but do you subtract test subject CPM from background CPM? (55 CPM minus 38 CPM to get 17 CPM in food sample). If so, would 17 CPM be safe or is any number above background unsafe?
At what level of CPM over background be cause for concern?
You see lots of stuff on the Internet and hear stuff from people. Thank you for your input.