We have parameterized the times to arc formation in CO2 : N2 : He mixtures using a TEA configuration which produces homogeneous 10‐liter laser discharges. The onset of arcing is suppressed by increasing the helium or decreasing the CO2concentration. Arcs are also suppressed by adding a low‐ionization‐potential seedant such as tripropylamine. Direct variation of the uv spark intensity which establishes the initial preionization has minimal impact on the arc formation process.