Long distance radiation detection, David Hahn and the clock The strange character David Hahn, obsessed with creating a nuclear reactor since a young age, was reportedly wandering around his neighborhood with a Geiger counter and by this means he located a source of radiation which turned out to be a vial of radium paint accidentally left inside an antique clock by a dial painting worker. The clock was sitting on a shelf in an antique store. This is how the event was described:

David began visiting junkyards and antiques stores in search of
  radium-coated dashboard panels or clocks. Once he found such an item,
  he’d chip paint from the instruments and collect it in pill vials. It
  was slow going until one day, driving through Clinton Township to
  visit his girlfriend, Heather, he noticed that his Geiger counter went
  wild as he passed Gloria’s Resale Boutique/Antique. The proprietor,
  Gloria Genette, still recalls the day when she was called at home by a
  store employee who said that a polite young man was anxious to buy an
  old table clock with a tinted green dial but wondered if she’d come
  down in price. She would. David bought the clock for $10. Inside he
  discovered a vial of radium paint left behind by a worker either
  accidentally or as a courtesy so that the clock’s owner could touch up
  the dial when it began to fade.

From this account it appears he detected the radium vial inside the store from a car driving by in the street perhaps 30 feet away. Since he was driving by there would have only been a short time register the activity.
This kind of confused me because in watching YouTube videos on radiation and Geiger counters, the counts seem to quickly drop off as soon as the wand is taken away. For example, with the alpha emitters the Geiger counter does not even react until the wand is an inch or so away from the emitter and the with the beta emitter maybe 3 inches or so. Given this highly limited range, how could Hahn have detected the radium from such a long distance away?
 A: As @dmckee pointed out in his comment, Radium is just at the "top of the decay chain". Specifically the decay chain looks like this source

Now these decays all look like $\alpha$ and $\beta$ emissions - none of which could be detected from any distance (since both are massive charged particles, they lose a lot of energy over a short range).
We need to dig a level deeper into the decay schemes to find the $\gamma$ radiation that can be detected at a distance.
For example, there is a wonderful resource at this link that allows you to explore the decay scheme of any isotope. If you click on the $\rm{^{222}Rn}$ entry in the isotope table (you may need to zoom in a bit to find it...), then select the "gamma" tab below, you see the following (only a partial screen shot shown):

Clearly, there are significant gamma emissions in the decay of radon - the daughter of $\rm{^{266}Ra}$ which is the first stop in the decay chain.
The 186.4 keV gamma (100% intensity - i.e. one generated for every decay) and the 262 keV gamma (intensity 134%, so more than one per decay on average) should have sufficient penetrating power that they can be picked up with a geiger counter from some distance away. Of course the inverse square law still (and always) plays a role, so there will be a significant drop-off with distance; but if the radium paint was reasonably concentrated, it's possible there would be sufficient gammas to detect the pot of paint "from a distance". There are many higher energy gammas as well, but they might be sufficiently energetic that a good fraction of them go right through the geiger counter without being detected.
Note that $\rm{^{266}Ra}$ itself also has a number of gammas in the emission scheme, including a 100% intensity peak at 67.67 keV and 143.87 keV peak - so just because the gammas are not mentioned in simplified diagrams, that doesn't mean they are not there. In fact they are everywhere...
