Ionization by electron collisions is important if the gas temperature approaches a fraction of the ionization threshold energy of the most abundant ions in the gas. For ground states we include the rates from [Raymond and Smith 1986] for elements other than iron, and from [Arnaud and Raymond 1992] for iron. Collisional ionization from excited levels may also be important to the ionization balance. We include ionization rates for all excited levels of every ion using approximate formulae by D. Sampson and coworkers ([Zhang and Sampson, 1987]). 3-body recombination rates to all levels are calculated from the collisional ionization rates using the detailed balance principle.