On 3/24/2011 the alarm on my Geiger Counter/Dosimeter sounded when radiation levels exceeded the default threshold level of .30 μSv/h (microsieverts/hour).

Later that afternoon I recorded spikes of 565 times normal (50.85 μSv/h microsieverts/hour), but only for a few seconds. Normal is usually .09 μSv/h. There was definitely some VERY hot particles in the air that day, although very diluted. I had to disable the alarm, as it was keeping me from sleeping that night.

I got a few alarms the next day (3/25) and it has been quiet ever since.