Here is a picture of one of my basement unit, not currently online. Pictured is a Holmes HEPA air purifier with a GMC-200 connected to (not pictured) a Raspberry Pi running custom NETC software.

The particles with radiation are trapped in the HEPA filter around the geiger counter.

Sorry about the poor quality. I did a zoom first then used heavy compression to reduce the file size to save bandwidth on the forum.

@KingCobra, yes I agree. The filter is standard gauze. I'll add another layer or two so that air still passes through, but achieves what you describe. Thanks for checking it out. I already see a difference in the way the data graph is being rendered. I'll keep tinkering with your thoughts in mind.

You could also buy the largest high quality furnace filter and cut it up to use as your filter material.

Oh that's a great idea. I'll post when I've installed the furnace filter.

I was washing some towels last night. As I was cleaning out the lint trap, I realized the thick half inch of clean white fiber would be a good temporary medium to trap all kinds of particles for monitoring. I tested the fiber with my Inspector EXP and didn't pick up anything beyond the background I usually get. I fashioned a new filter and positioned it right up to the tube in the GMC-320. Seems like I did it just in time as the equipment picked up a plume of something over the last 24 hours. In these situations, it would be nice to have a scintillator to get an idea of what's being detected.

The new tweeks seemed to work. My station is now rendering a chart that seems to match what EPA stations are picking up on. And judging from those charts, it's a bad day to be an aerobic organism... I wonder if the Jetstream http://squall.sfsu.edu/gif/jetstream_norhem_00.gif has any role in today's hot airborne particles. Maybe the radon from Porter Ranch is a part of these measurements. I wonder...

Here is a site that I find very useful for all types of atmospheric modeling. The bottom left corner has a menu that exposes a ton of options. This link should open it up at the Jetstream model.
http://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=-141.88,21.91,262

yes nullschool.net is amazing. thanks for the direct jetstream link