Well, I think Sterno is basing their claim on laboratory tests. In those tests, there must have been plenty of oxygen available while the Sterno was aflame. If your theory is correct, and it sure sounds reasonable to me, the only way they could measure zero carbon dioxide is if there weren't an instance during the testing when oxygen levels ran low, or below a certain (unknown) threshhold.

For our coleague fesigohl, who is probably right now sleeping in the van with 2 large, oxygen-sucking dogs, and with him sucking up his own share, we need to know how much oxygen must be available to save the three of them from carbon monoxide poisoning. He mentioned cracking a window, maybe two. Plus, there should be other intake ports where fresh air (and oxygen) are taken into the van.

Now, if someone were to use a carbon monoxide detection device, in a van, whilst burning Sterno, and the device were to register zero (or negative) for the presence of carbon monoxide, he would have some basis for refuting your claim, or at least making some oxygen variant arguement. If the device showed the presence of carbon monoxide, he could send that in to Sterno and say, "See! Your independant laboratory tests are b.s.!", or something silly like that.

I feel like I'm suffering from carbon monoxide poisoning right now.