  Time evolution of the ionization state of metals in the cosmic baryons is
investigated in a cosmological context without the assumption of ionization
equilibrium. We find that a significant fraction of ionized oxygen ions (OVII
and OVIII) in the warm-hot intergalactic medium (WHIM) is not in the ionization
equilibrium state at a redshift of z~0. We also investigate the effect on the
detectability and observables of WHIM as a consequence of such deviation from
ionization equilibrium. It is found that the detectability of WHIM is not
altered very much both through its emission and absorption signatures, but line
ratios between OVII and OVIII are significantly different from those in the
ionization equilibrium state.
