content: Basics of Radiation Exposure & home Geiger counters https://www.gunsamerica.com/blog/smart-geiger-counter-for-android-iphone-review/ Some good basics about the different types of radiation. Worth saving to your offline disaster preparedness materials. I am also curious if anyone here has any recommendations for inexpensive Geiger counters. The type that plug into a phone seem like a good deal, but they aren't useful for 'site surveying' and immediate aftermath of disaster.