I've been to two major events so far, Thunder in the Mountains 2016  and COPE 2016, and I've been offering free testing for Violet wand  output and for gapped electrodes like body contacts. 

The function of the safety gap in such electrodes is to prevent the  low voltage from the wall plug from conducting through the person. The  gap needs to be small enough so that when the high voltage fires across  the gap the energy lost in the gap is minimal, but large enough that the  peak line voltage (which could be as high as 325V on a 230V line or  170V on a 120V line) can't sustain the spark when the high voltage is  not present.   

This is the same reason that fuses have voltage ratings.   A 32V automotive fuse is not guaranteed to be able to stop the current  in a circuit with higher voltage like a 120V AC line. Arcing may allow  current to continue to flow through the blown fuse! 

I've tested maybe 20 body contacts at these two events, and two of those were defective,  with the safety gap shorted.  That is not a comforting number.  This is  better odds than "Russian Roulette". but not much better. 

I have not had the opportunity to dissect those failed pieces, which  would have been interesting. I can easily predict a couple of failure  mechanisms though: 

1: Carbon tracking across a plastic insulator.  When a flush cut wire  end is used as the gap, the spark will end up running over the surface  of the plastic. The heat and ozone from the spark will carbonize the  plastic over time, turning it into a conductor.  This is similar to the  carbon tracking that happens on spark plug boots, wires and distributor  caps. 

2: Errant wires.  Any wire projecting out past the plastic could over  time, with flexing of the body contact cable, bend slightly and short  to the outer contact. 

3: Other manufacturing defect or use driven failure mechanism. 

There are a number of vendors making these devices, and I can't  possibly know all the techniques that they might have used to create the  spark gap. No matter what the failure mechanism, the effect is the same, the  safety gap no longer works as it should but the worst part is that the  user has no idea this has happened.  A safety barrier has been removed  without your knowledge. 

What do you do about it: Test your equipment.  The required equipment (a 1000V "megger") isn't  expensive.  $20-$30  A group could buy one and let the members use it  at munches and play parties.  The "megger" builds up 1000V and places  that across the test leads. You connect one lead to each end of your  body contact or other gapped electrode, and the meter reads out what the  resistance is.  It should read "1     " which indicates open circuit.  A  lower reading indicates that current is leaking through, probably due  to carbon tracking, or maybe contamination like dirt or moisture inside  the gap assembly. 

I developed my "Clearview Spark Gap" because of these issues,  The  gap material is borosilicate glass which simply will not develop carbon  tracking, and the gap spacing is determined by the diameter of the  spheres, which won't change over time.  It simply won't fail in a way  that would be dangerous.