Air Filter Readings


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In the first reading, the goal was to establish a baseline. The geiger counter was placed on the metal surface of a potting table on the back porch. The table was wiped clean before beginning. Multiple readings were taken. As you can see, the readings range from .009 to .013 mR/hr. The fifth reading was done with the back cover open so as to detect alpha radiation. As you can see, the reading was consistent with the others: .009 mR/hr.

Please note: the changes in readings do not indicate poor performance in the detector. The device counts "hits" by radiation. The rate of emissions and direction are not constant so an unfortunate encounter — such as occurs when inhaling or ingesting a particle — are basically random events. In short, all the geiger counter can do it measure the number of such random encounters it has.

The next two readings were taken of a new filter in its original packaging. You can see that the measurements remained more or less the same as with the other readings. Note the back cover is open.

Now we are going to look at the used filter, removed on June 14, 2011.

Note that with the back cover open, the readings ranged from .013 to .025 mR/hr. It is possible that the method used was flawed because even the very thin packaging material might block alpha particles, but decontamination would be very difficult without that thin sheeting.

With the back cover closed, the readings ranged from .007 to .014 mR/ hr.

Since what would be most dangerous is the rumored alpha particles, said to have amounted to several per day in the Seattle area, this test was conducted to determine the likelihood that potentially dangerous alpha particles were present in the home.

To understand this better, please listen to the videos produced by Arne Gundersen and posted on his web site as well as and elsewhere.



The average person probably breaths about 10,000 liters of air per day. Obviously, this varies enormously based on the activities of the individual, i.e. sitting versus exertion. It varies according to the size of the individual, age, gender, and breathing habits. So, a rough estimate of 10,000 liters per day is very conservative. The number could actually be double or even triple the average.

However, based on examination of filters in homes and automobiles as well as more sophisticated air testing devices, it has been variously estimated that people in the Seattle area inhaled 5-20 hot particles per day due to the nuclear disaster in Fukushima.


The subject house is on the Kitsap Peninsula across Puget Sound from Seattle. One should expect variations in readings due not only to wind and weather but also location, use of doors and windows, traffic in and out of the house, and more subtle factors such as building materials. It would be logical if carpeted rooms have a higher concentration of particulates than rooms with easier to clean surfaces such as room and tile. The house in question has no carpeting. In addition, it has a powerful filtration system and sealed crawl space, measures deemed necessary after a rendezvous with mold.

Since hot particles would normally precipitate, it is reasonable to expect that more people going in and out as well as wearing shoes in the house would increase the presence of particulates.


test of the geiger counter using radioactive beads || Rock Dust Measurements


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