Radioactivity is always and everywhere. It originates mainly from the universe, are in lower proportions of objects but also the work of humans. Normally it is safe, because the so-called background radiation is so weak that you can not harm the earth's inhabitants.
The radiation is measured with "Geiger counters" and usually has a value of 0.10 to 0.20/h  µSv/h (nuclear micro Sievert per hour).
Every now and again increases the radiation - caused by malfunctions of equipment, which were created by humans,  or are taken  -  such as nuclear power plants,   transportation of  "nuclear waste"  and in the

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vicinity of nuclear waste repositories - to values ​​which necessitates a warning to the population so that people can immediately initiate protective measures. The warnings are mandatory because humans have no sense organ for the feel of harmful radiation. The radiation is invisible, it does not smell, it is silent and is neither cold nor hot. But it can cause serious permanent damage to living creatures, with very high values, it is also deadly. Insidious is the fact that the radiation is stored in a certain degree of pre-irradiated substances such as water, rocks and plants and can radiate from there (ingestion).
To be dependent not only on the warnings of the authorities I had long been the desire to continuously monitor the radiation so that I can immediately see if the normal background radiation suddenly and longer lasting than average rises above safe levels. In a separate observation period can be seen that the radiation is not constant, but may also have short radiation peaks, which can significantly exceed the average duration. These short tips - if they do not have very high values ​​and are not repeated at short intervals (in minutes) - are not dangerous. But it could herald a trend change.