We demonstrate a direct and stable aerosol synthesis of single-walled carbon nanotubes (SWCNTs) using a hot wire generator (HWG) method, with iron physically evaporated in a carbon monoxide (CO) atmosphere as the catalyst source. A small amount of added carbon dioxide increased the lifetime of the Fe wire in reacting CO up to several weeks. This approach allowed us to significantly increase the yield of SWCNTs as compared to the previously employed inert hydrogen-containing flow through the wire. High quality and purity SWCNTs were produced, as demonstrated by high-resolution transmission electron microscopy and Raman and optical absorption spectroscopy.