> impedance. Ceramic tiles are good insulators BUT dirt and moisture will
> provide leakage paths.

I disagree strongly. Ceramic tiles are highly conductive for leakage
current esp. when laid on concrete or bare ground, at normal humidity
levels, in despite of the normal layer of sand under them. Only glazed
ceramic tiles are good insulators. Glazed ceramic is seldomly used for
floors because it is one of the most slippery floors possible, and it has
to be structured to prevent slipping. It is used in chemical labs and such
where hot corrosive things spill on it from time to time, and soaking that
in is not desirable (normal terra cotta tiles have pores and soak
everything in so you can't ever get it out again).

We have ceramic tile floors here and I have learned the hard way it's not
a good insulator, even when dry. Linoleum, *some* rubber mats/carpets
(incidentally, not the antistatic ones !), wood parquette and cork panel
floors are reasonably good insulators, when dry. Everything else is a
conductor from this point of view. When I need to touch HV I stand on an
inverted bottle crate (hard PVC about 40 cm tall and very sturdy) and use
only one hand. I also use a HDPE kitchen cutting board on the table when I
work with exposed HV circuits. It prevents any surprises from the wooden
tabletop (humidity can be 95% at times here).

Peter

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