Geiger counters are more sensitive I read after a friend mentioning it and set alarms on relatively safe numbers because there in fractional numbers. She showed me one that goes up to 10 though instead of just one before it will reach it’s level.
Here’s what she said so I don’t have to paraphrase. After this I’ll just drop the conversation about it except to her. They even have a book diets on what to eat after a blast and not to eat I remember maybe 15 or more years ago. Lots of books on it and probably get the one on. Normal ranges and exposures that in the 50s they didn’t know yet I hope they still have it…
background radiation (normal) is. That way, if you see it start to go up, you know radiation is coming in. It will zero out when it reaches its radiation limit. All you will know then is that more than 1 or whatever roentgens per hour are coming in.
See if you can find something with enough radiation but still safe to see when it zeros out so you’ll know what level it reaches.

