I was purely wondering about the mats, which are not conductive enough to cause any problems when you touch mains.
Top layer, sure, as it's in the 10^8 Ohm range. But do keep in mind that the bottom conductive layer is only in the 10^5 Ohm range. Quick measurement on one of mine indicates ~20k, so a 1M in the ground cord is actually a good idea (technically, the resistor is optional, but usually present IME).
And it seems that most kits come with a 1M resistive cable (black wire = 1M resistor; green w/ yellow stripe = no resistor).
NASA's
MSFC-RQMT-2918 document may be of some interest (direct .pdf link).
But the comment about high voltage behaviour (which is exactly what the mats are supposed to remove) made me wonder how quickly they are supposed to remove static charge. Gotta get my hands on those standards.
If I understand what you're looking for,
http://www.esdjournal.com/techpapr/ryne/rynedisc.htm gives you those specs.
Worst case Human Body Model (HBM), is a discharge of 6.2mJ, and the discharge rate cannot go below 2.01ms. Anything faster than that, and you get an ESD event.
Hope this helps.
Also have good bought qute a few ESD mats from this guy there farly nice quality and the connector they come with already has the 1mohm resistor in the cable. There significantly cheaper than digkey or mouser when i looked last
http://www.ebay.com/usr/canvu0_0?_trksid=p2047675.l2559
I've bought from this seller as well. Good quality mat at decent prices.
Only time I've beaten his pricing, was with a closeout mat from all-spec (got one hell of a deal this way; paid ~ 35 - 40% of retail IIRC).