local medical procedure. This demonstrates the ability of this pilot program to detect even small amounts of radioactivity. A stationary monitor, say in the center of a city on a tall building, may not see such a release as a result of dilution and distance from the source. However, in this scenario, a police cruiser was likely near the hospital in which this isotope was released as part of a medical treatment. However, it should be noted, short lived isotopes including $^{131}$I (t$_{1/2}=$ 8 days) could be difficult to detect using automobile filters, since they can decay away before regular maintenance may occur to replace filters in vehicles.

![A gamma ray spectrum from April 7, 2011 obtained from counting an automobile filter from a Berkeley Police Department patrol vehicle. Fission products were easily identifiable in the aftermath of the radiation release. More information on the peaks displayed here are listed in [**Table \[tab:isotopes\]**]{}.[]{data-label="fig:autofilter"}](26165S-AutoFilter){width="\linewidth"}

![Counting rates for fission products from Fukushima as seen on automobile filters in Berkeley, CA. The day plotted for filters represents the date after 3/11/11 when the filter was removed from a vehicle. Counting rates were not converted to airborne activity, as the full mileage (and hence 