  We formulate the kinetic master equation describing the production of charged
particles which are created or destroyed only in pairs due to the conservation
of their Abelian charge.Our equation applies to arbitrary particle
multiplicities and reproduces the equilibrium results for both canonical (rare
particles) and grand canonical (abundant particles) systems. For canonical
systems, the equilibrium multiplicity is much lower and the relaxation time is
much shorter than the naive extrapolation from the grand canonical ensemble
results. Implications for particle chemical equilibration in heavy-ion
collisions are discussed.
