Further studies are reported on a novel room temperature tin oxide-platinum sensor for carbon monoxide (CO). The expected porous nature has been confirmed by scanning electron microscope pictures of these sensors. Pore sizes were 0.1-10 mu m. Recovery studies confirm that high resistance sensors recover more quickly. During the recovery a second fire can be detected and there are no signs of self-poisoning by CO. Preliminary results are presented for temperature and humidity cycling. (C) 1998 Chapman & Hall.