I think we discussed this before on this list. Anyway, I can verify that
John Denker's response is on target with my experience. I was once "in the
business" of making nuclear detectors, and I solved quite a few problems
with high voltage (up to 50 kV in spaces as tiny as one centimeter yielding
electric fields at least as high as 10E6 volts per meter).
Humid air is not more conductive than dry air. Humid conditions can lead to
increased current along the surfaces of insulators, but the effect is not
much if the surfaces are clean. If the surfaces are "dirty" then the
increased water film on the surface (that can be present with high humidity)
can dissolve enough ions from the dirt to make a conductive path along the
surface.
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817