|In order to understand plasma chemistry in the plasmas which contain water
vapor, we construct a mode for describe chemical reactions involved in
such plasmas. As described in many published reports on the plasma involving
water, OH radicals are regarded as important species for oxidation or the
other treatment of materials. However, their life-time is known to be very
short. In order to know actual life time in after glow and diffusion length
from discharge area, we have performed zero and one dimensional calculation
of the density of major species in the plasma.