From the Sterno people
http://www.sterno.com/pro/pages/gel.html* Ethanol-based gel is nonexplosive and nontoxic
* Odor-free, smoke-free, carbon monoxide-free
* Resealable and reusable: Packaging made from reusable or recyclable materials
* Consistent BTUs keep food in the temperature safety zone *141°F+
* Delivers hottest maximum temperature with no spills or flare-ups
From PubMed
http://www.ncbi.nlm.nih.gov/pubmed/638911"A high school student became ill and later unconscious while working over a heating table set over three cans of burning Sterno. Measurements of 1000 to 3000 parts per million of carbon monoxide were obtained around and above the apparatus. Although the room was well ventilated there was incomplete combustion of the canned heating fuel because the apparatus was surrounded by aluminum foil, which resulted in poor oxygenation of the flame area. This case demonstrates the hazards of carbon monoxide poisoning from incompletely burned Sterno."
Carbon monoxide isn't always the problem. Everything that burns requires oxygen to do it. People require oxygen, too. Well-sealed house + Sterno burning + people breathing might cause some problems.
Sue