Use your car's engine and cabin filters to track your fallout exposure

If you are concerned about radioactive exposure, please go purchase new engine and cabin air filters (if equipped) for your car. Record the installation date(s); keep track of how many miles and how many days you have on it; when it comes time to replace it, bag it in a zip lock and store the data with it. This may provide a historical record for your exposure to radioactive fallout particulate.

If you have a Geiger counter, test those air filters for contamination based on a repeatable sampling cycle. For example, test the filters every 250 miles and every 7 days. If you are not detecting any fallout, increase the intervals to every 500 miles and every 14 days. If you start noticing an increase in contamination start checking using a more frequent cycle.

It also would not hurt to keep a few spare filters on hand for your vehicles in case they do get contaminated.


Fortunately, for some unknown reason I have been keeping my old air filters and can establish a pre-Fukushima baseline. On my current post Fukushima engine air filter, I did find one small hot spot which read 0.015 mR/hr. The rest of the filter had readings between 0.006-.010 mR/hr.

The best way I have found to check a filter is to slowly run over its surface looking for spots that can be repeatedly detected on the Geiger counter. After those locations have been noted they should be tested for a longer duration. Ideally one would use a Geiger counter with a large pancake sensor for those purposes.