All the suggestions here are great. While reading this thread, I remembered John Blichmann's presentation at the 2010 NHC entitled "Tips and Tricks to Setting up your own Homebrewery" which covers some of the issues of a basement brewery and is worth a read (or re-read). If interested, you can view the presentation on this website, just choose "Events", then "Seminar Presentation," then "2010". Don't forget that in addition to post-combustion gases and potential propane leaks, process steam must also be vented. So even electric brewing doesn't eliminate the need for an adequate exhaust system.
I decided that garage brewing isn't so bad afterall . . . .