Can you better explain how these alerts start, and why they are canceled?

Answer:
Netc.com tracks the radiation levels at over 3000 stations around the world. Some of the stations, collect gamma radiation and others collect dose rates. Each station has its own NORM (Natural Occurring Radiation Material) background level that is calculated everyday for three months. When the current radiation exceeds that level and other conditions are met, an Alert in issue: Saying the radiation at that station has increased radiation level that are higher the the 3 month range. This is very important, not because it is dangerous, but because high levels of radiation blows in the wind or rain and could be a health problem if it is breathe into your lungs. Just like a sand storm the radiation blows following the wind patterns, so then the Alert is cancelled when the radiation is within its radiation level.