That is more a vapor planet rather than a true gas planet. Think of it as an Ice planet or water world with a runaway greenhouse effect.
Edit: This is not to say true gas planets can't get very small under the right circumstances.
TonioDeter wrote:You guys should read the first post of this topic before calling an atmosphere breathable. You forgot to take the SO2 into account, its pressure has to be below 5.10^-6 at worst, and below 1.10^-6 to be comfortable.